Title: Elements of Chemistry,
Author: Antoine Laurent Lavoisier
Translator: Robert Kerr
Release date: December 28, 2009 [eBook #30775]
Most recently updated: January 5, 2021
Language: English
Credits: Produced by Mark C. Orton, Josephine Paolucci and the
Online Distributed Proofreading Team at https://www.pgdp.net
Member of the Academy of Sciences, Royal Society of Medicine, andAgricultural Society of Paris, of the Royal Society of London, andPhilosophical Societies of Orleans, Bologna, Basil, Philadelphia,Haerlem, Manchester, &c. &c.
Member of the Royal College of Surgeons, and Surgeon to the OrphanHospital of Edinburgh.
EDINBURGH:printed for WILLIAM CREECH, and sold in london by g. g. andj. j. robinsons.
MDCCXC.
[Pg v]
The very high character of Mr Lavoisier as a chemical philosopher, andthe great revolution which, in the opinion of many excellent chemists,he has effected in the theory of chemistry, has long made it muchdesired to have a connected account of his discoveries, and of the newtheory he has founded upon the modern experiments written by himself.This is now accomplished by the publication of his Elements ofChemistry; therefore no excuse can be at all necessary for giving thefollowing work to the public in an English dress; and the onlyhesitation of the Translator is with regard to his own abilities for thetask. He is most ready to confess, that his knowledge of the composition[Pg vi]of language fit for publication is far inferior to his attachment tothe subject, and to his desire of appearing decently before the judgmentof the world.
He has earnestly endeavoured to give the meaning of the Author with themost scrupulous fidelity, having paid infinitely greater attention toaccuracy of translation than to elegance of stile. This last indeed, hadhe even, by proper labour, been capable of attaining, he has beenobliged, for very obvious reasons, to neglect, far more than accordedwith his wishes. The French copy did not reach his hands before themiddle of September; and it was judged necessary by the Publisher thatthe Translation should be ready by the commencement of the UniversitySession at the end of October.
He at first intended to have changed all the weights and measures usedby Mr Lavoisier into their correspondent English denominations, but,upon trial, the task was found infinitely too great for the timeallowed; and to have executed this part of the work inaccurately, musthave been both useless and misleading to the reader. All that has beenattempted in this way is adding, between brackets ( ), the degrees ofFahrenheit's[Pg vii] scale corresponding with those of Reaumeur's thermometer,which is used by the Author. Rules are added, however, in the Appendix,for converting the French weights and measures into English, by whichmeans the reader may at any time calculate such quantities as occur,when desirous of comparing Mr Lavoisier's experiments with those ofBritish authors.
By an oversight, the first part of the translation went to press withoutany distinction being preserved between charcoal and its simpleelementary part, which enters into chemical combinations, especiallywith oxygen or the acidifying principle, forming carbonic acid. Thispure element, which exists in great plenty in well made charcoal, isnamed by Mr Lavoisiercarbone, and ought to have been so in thetranslation; but the attentive reader can very easily rectify themistake. There is an error in Plate XI. which the engraver copiedstrictly from the original, and which was not discovered until the platewas worked off at press, when that part of the Elements which treats ofthe apparatus there represented came to be translated. The two tubes 21.and 24. by which the gas is conveyed[Pg viii] into the bottles of alkalinesolution 22. 25. should have been made to dip into the liquor, while theother tubes 23. and 26. which carry off the gas, ought to have been cutoff some way above the surface of the liquor in the bottles.
A few explanatory notes are added; and indeed, from the perspicuity ofthe Author, very few were found necessary. In a very small number ofplaces, the liberty has been taken of throwing to the bottom of thepage, in notes, some parenthetical expressions, only relative to thesubject, which, in their original place, tended to confuse the sense.These, and the original notes of the Author, are distinguished by theletter A, and to the few which the Translator has ventured to add, theletter E is subjoined.
Mr Lavoisier has added, in an Appendix, several very useful Tables forfacilitating the calculations now necessary in the advanced state ofmodern chemistry, wherein the most scrupulous accuracy is required. Itis proper to give some account of these, and of the reasons for omittingseveral of them.[Pg ix]
No. I. of the French Appendix is a Table for converting ounces, gros,and grains, into the decimal fractions of the French pound; and No. II.for reducing these decimal fractions again into the vulgar subdivisions.No. III. contains the number of French cubical inches and decimals whichcorrespond to a determinate weight of water.
The Translator would most readily have converted these Tables intoEnglish weights and measures; but the necessary calculations must haveoccupied a great deal more time than could have been spared in theperiod limited for publication. They are therefore omitted, asaltogether useless, in their present state, to the British chemist.
No. IV. is a Table for converting lines or twelfth parts of the inch,and twelfth parts of lines, into decimal fractions, chiefly for thepurpose of making the necessary corrections upon the quantities ofgasses according to their barometrical pressure. This can hardly be atall useful or necessary, as the barometers used in Britain are graduatedin decimal fractions of the inch, but, being referred to by the Authorin[Pg x] the text, it has been retained, and is No. I. of the Appendix tothis Translation.
No. V. Is a Table for converting the observed heights of water withinthe jars used in pneumato-chemical experiments into correspondentheights of mercury for correcting the volume of gasses. This, in MrLavoisier's Work, is expressed for the water in lines, and for themercury in decimals of the inch, and consequently, for the reasons givenrespecting the Fourth Table, must have been of no use. The Translatorhas therefore calculated a Table for this correction, in which the wateris expressed in decimals, as well as the mercury. This Table is No. II.of the English Appendix.
No. VI. contains the number of French cubical inches and decimalscontained in the corresponding ounce-measures used in the experiments ofour celebrated countryman Dr Priestley. This Table, which forms No. III.of the English Appendix, is retained, with the addition of a column, inwhich the corresponding English cubical inches and decimals areexpressed.[Pg xi]
No. VII. Is a Table of the weights of a cubical foot and inch, Frenchmeasure, of the different gasses expressed in French ounces, gros,grains, and decimals. This, which forms No. VI. of the English Appendix,has been, with considerable labour, calculated into English weight andmeasure.
No. VIII. Gives the specific gravities of a great number of bodies, withcolumns, containing the weights of a cubical foot and inch, Frenchmeasure, of all the substances. The specific gravities of this Table,which is No. VII. of the English Appendix, are retained, but theadditional columns, as useless to the British philosopher, are omitted;and to have converted these into English denominations must haverequired very long and painful calculations.
Rules are subjoined, in the Appendix to this translation, for convertingall the weights and measures used by Mr Lavoisier into correspondingEnglish denominations; and the Translator is proud to acknowledge hisobligation to the learned Professor of Natural Philosophy in theUniversity of Edinburgh, who kindly supplied him with the necessaryinformation for this purpose. A Table is likewise added, No. IV. of[Pg xii] theEnglish Appendix, for converting the degrees of Reaumeur's scale used byMr Lavoisier into the corresponding degrees of Fahrenheit, which isuniversally employed in Britain[1].
This Translation is sent into the world with the utmost diffidence,tempered, however, with this consolation, that, though it must fallgreatly short of the elegance, or even propriety of language, whichevery writer ought to endeavour to attain, it cannot fail of advancingthe interests of true chemical science, by disseminating the accuratemode of analysis adopted by its justly celebrated Author. Should thepublic call for a second edition, every care shall be taken to correctthe forced imperfections of the present translation, and to improve thework by valuable additional matter from other authors of reputation inthe several subjects treated of.
Edinburgh, }
Oct. 23. 1789. }
[1] The Translator has since been enabled, by the kindassistance of the gentleman above alluded to, to give Tables, of thesame nature with those of Mr Lavoisier, for facilitating thecalculations of the results of chemical experiments.
[Pg xiii]
When I began the following Work, my only object was to extend andexplain more fully the Memoir which I read at the public meeting of theAcademy of Sciences in the month of April 1787, on the necessity ofreforming and completing the Nomenclature of Chemistry. While engaged inthis employment, I perceived, better than I had ever done before, thejustice of the following maxims of the Abbé de Condillac, in his Systemof Logic, and some other of his works.
"We think only through the medium of words.—Languages are trueanalytical methods.—Algebra,[Pg xiv] which is adapted to its purpose in everyspecies of expression, in the most simple, most exact, and best mannerpossible, is at the same time a language and an analytical method.—Theart of reasoning is nothing more than a language well arranged."
Thus, while I thought myself employed only in forming a Nomenclature,and while I proposed to myself nothing more than to improve the chemicallanguage, my work transformed itself by degrees, without my being ableto prevent it, into a treatise upon the Elements of Chemistry.
The impossibility of separating the nomenclature of a science from thescience itself, is owing to this, that every branch of physical sciencemust consist of three things; the series of facts which are the objectsof the science, the ideas which represent these facts, and the words bywhich these ideas are expressed. Like three impressions of the sameseal, the word ought to produce the idea, and the idea to be a pictureof the fact. And, as ideas are preserved and communicated by means ofwords, it necessarily follows[Pg xv] that we cannot improve the language ofany science without at the same time improving the science itself;neither can we, on the other hand, improve a science, without improvingthe language or nomenclature which belongs to it. However certain thefacts of any science may be, and, however just the ideas we may haveformed of these facts, we can only communicate false impressions toothers, while we want words by which these may be properly expressed.
To those who will consider it with attention, the first part of thistreatise will afford frequent proofs of the truth of the aboveobservations. But as, in the conduct of my work, I have been obliged toobserve an order of arrangement essentially differing from what has beenadopted in any other chemical work yet published, it is proper that Ishould explain the motives which have led me to do so.
It is a maxim universally admitted in geometry, and indeed in everybranch of knowledge, that, in the progress of investigation, we shouldproceed from known facts to what is unknown. In early infancy, our ideasspring from our wants; the sensation of want excites the idea of[Pg xvi] theobject by which it is to be gratified. In this manner, from a series ofsensations, observations, and analyses, a successive train of ideasarises, so linked together, that an attentive observer may trace back toa certain point the order and connection of the whole sum of humanknowledge.
When we begin the study of any science, we are in a situation,respecting that science, similar to that of children; and the course bywhich we have to advance is precisely the same which Nature follows inthe formation of their ideas. In a child, the idea is merely an effectproduced by a sensation; and, in the same manner, in commencing thestudy of a physical science, we ought to form no idea but what is anecessary consequence, and immediate effect, of an experiment orobservation. Besides, he that enters upon the career of science, is in aless advantageous situation than a child who is acquiring his firstideas. To the child, Nature gives various means of rectifying anymistakes he may commit respecting the salutary or hurtful qualities ofthe objects which surround him. On every occasion his judgments arecorrected by experience; want and pain are the necessary[Pg xvii] consequencesarising from false judgment; gratification and pleasure are produced byjudging aright. Under such masters, we cannot fail to become wellinformed; and we soon learn to reason justly, when want and pain are thenecessary consequences of a contrary conduct.
In the study and practice of the sciences it is quite different; thefalse judgments we form neither affect our existence nor our welfare;and we are not forced by any physical necessity to correct them.Imagination, on the contrary, which is ever wandering beyond the boundsof truth, joined to self-love and that self-confidence we are so apt toindulge, prompt us to draw conclusions which are not immediately derivedfrom facts; so that we become in some measure interested in deceivingourselves. Hence it is by no means to be wondered, that, in the scienceof physics in general, men have often made suppositions, instead offorming conclusions. These suppositions, handed down from one age toanother, acquire additional weight from the authorities by which theyare supported, till at last they are received, even by men of genius, asfundamental truths.[Pg xviii]
The only method of preventing such errors from taking place, and ofcorrecting them when formed, is to restrain and simplify our reasoningas much as possible. This depends entirely upon ourselves, and theneglect of it is the only source of our mistakes. We must trust tonothing but facts: These are presented to us by Nature, and cannotdeceive. We ought, in every instance, to submit our reasoning to thetest of experiment, and never to search for truth but by the naturalroad of experiment and observation. Thus mathematicians obtain thesolution of a problem by the mere arrangement of data, and by reducingtheir reasoning to such simple steps, to conclusions so very obvious, asnever to lose sight of the evidence which guides them.
Thoroughly convinced of these truths, I have imposed upon myself, as alaw, never to advance but from what is known to what is unknown; neverto form any conclusion which is not an immediate consequence necessarilyflowing from observation and experiment; and always to arrange thefacts, and the conclusions which are drawn from them, in such an orderas shall render it most easy for beginners in the[Pg xix] study of chemistrythoroughly to understand them. Hence I have been obliged to depart fromthe usual order of courses of lectures and of treatises upon chemistry,which always assume the first principles of the science, as known, whenthe pupil or the reader should never be supposed to know them till theyhave been explained in subsequent lessons. In almost every instance,these begin by treating of the elements of matter, and by explaining thetable of affinities, without considering, that, in so doing, they mustbring the principal phenomena of chemistry into view at the very outset:They make use of terms which have not been defined, and suppose thescience to be understood by the very persons they are only beginning toteach. It ought likewise to be considered, that very little of chemistrycan be learned in a first course, which is hardly sufficient to make thelanguage of the science familiar to the ears, or the apparatus familiarto the eyes. It is almost impossible to become a chemist in less thanthree or four years of constant application.
These inconveniencies are occasioned not so much by the nature of thesubject, as by the method of teaching it; and, to avoid them, I[Pg xx] waschiefly induced to adopt a new arrangement of chemistry, which appearedto me more consonant to the order of Nature. I acknowledge, however,that in thus endeavouring to avoid difficulties of one kind, I havefound myself involved in others of a different species, some of which Ihave not been able to remove; but I am persuaded, that such as remain donot arise from the nature of the order I have adopted, but are ratherconsequences of the imperfection under which chemistry still labours.This science still has many chasms, which interrupt the series of facts,and often render it extremely difficult to reconcile them with eachother: It has not, like the elements of geometry, the advantage of beinga complete science, the parts of which are all closely connectedtogether: Its actual progress, however, is so rapid, and the facts,under the modern doctrine, have assumed so happy an arrangement, that wehave ground to hope, even in our own times, to see it approach near tothe highest state of perfection of which it is susceptible.
The rigorous law from which I have never deviated, of forming noconclusions which are not fully warranted by experiment, and of never[Pg xxi]supplying the absence of facts, has prevented me from comprehending inthis work the branch of chemistry which treats of affinities, althoughit is perhaps the best calculated of any part of chemistry for beingreduced into a completely systematic body. Messrs Geoffroy, Gellert,Bergman, Scheele, De Morveau, Kirwan, and many others, have collected anumber of particular facts upon this subject, which only wait for aproper arrangement; but the principal data are still wanting, or, atleast, those we have are either not sufficiently defined, or notsufficiently proved, to become the foundation upon which to build sovery important a branch of chemistry. This science of affinities, orelective attractions, holds the same place with regard to the otherbranches of chemistry, as the higher or transcendental geometry doeswith respect to the simpler and elementary part; and I thought itimproper to involve those simple and plain elements, which I flattermyself the greatest part of my readers will easily understand, in theobscurities and difficulties which still attend that other very usefuland necessary branch of chemical science.
Perhaps a sentiment of self-love may, without my perceiving it, havegiven additional force to[Pg xxii] these reflections. Mr de Morveau is atpresent engaged in publishing the articleAffinity in the MethodicalEncyclopædia; and I had more reasons than one to decline entering upon awork in which he is employed.
It will, no doubt, be a matter of surprise, that in a treatise upon theelements of chemistry, there should be no chapter on the constituent andelementary parts of matter; but I shall take occasion, in this place, toremark, that the fondness for reducing all the bodies in nature to threeor four elements, proceeds from a prejudice which has descended to usfrom the Greek Philosophers. The notion of four elements, which, by thevariety of their proportions, compose all the known substances innature, is a mere hypothesis, assumed long before the first principlesof experimental philosophy or of chemistry had any existence. In thosedays, without possessing facts, they framed systems; while we, who havecollected facts, seem determined to reject them, when they do not agreewith our prejudices. The authority of these fathers of human philosophystill carry great weight, and there is reason to fear that it will evenbear hard upon generations yet to come.[Pg xxiii]
It is very remarkable, that, notwithstanding of the number ofphilosophical chemists who have supported the doctrine of the fourelements, there is not one who has not been led by the evidence of factsto admit a greater number of elements into their theory. The firstchemists that wrote after the revival of letters, considered sulphur andsalt as elementary substances entering into the composition of a greatnumber of substances; hence, instead of four, they admitted theexistence of six elements. Beccher assumes the existence of three kindsof earth, from the combination of which, in different proportions, hesupposed all the varieties of metallic substances to be produced. Stahlgave a new modification to this system; and succeeding chemists havetaken the liberty to make or to imagine changes and additions of asimilar nature. All these chemists were carried along by the influenceof the genius of the age in which they lived, which contented itselfwith assertions without proofs; or, at least, often admitted as proofsthe slighted degrees of probability, unsupported by that strictlyrigorous analysis required by modern philosophy.[Pg xxiv]
All that can be said upon the number and nature of elements is, in myopinion, confined to discussions entirely of a metaphysical nature. Thesubject only furnishes us with indefinite problems, which may be solvedin a thousand different ways, not one of which, in all probability, isconsistent with nature. I shall therefore only add upon this subject,that if, by the termelements, we mean to express those simple andindivisible atoms of which matter is composed, it is extremely probablewe know nothing at all about them; but, if we apply the termelements,orprinciples of bodies, to express our idea of the last point whichanalysis is capable of reaching, we must admit, as elements, all thesubstances into which we are capable, by any means, to reduce bodies bydecomposition. Not that we are entitled to affirm, that these substanceswe consider as simple may not be compounded of two, or even of a greaternumber of principles; but, since these principles cannot be separated,or rather since we have not hitherto discovered the means of separatingthem, they act with regard to us as simple substances, and we oughtnever to suppose them compounded until experiment and observation hasproved them to be so.[Pg xxv]
The foregoing reflections upon the progress of chemical ideas naturallyapply to the words by which these ideas are to be expressed. Guided bythe work which, in the year 1787, Messrs de Morveau, Berthollet, deFourcroy, and I composed upon the Nomenclature of Chemistry, I haveendeavoured, as much as possible, to denominate simple bodies by simpleterms, and I was naturally led to name these first. It will berecollected, that we were obliged to retain that name of any substanceby which it had been long known in the world, and that in two cases onlywe took the liberty of making alterations; first, in the case of thosewhich were but newly discovered, and had not yet obtained names, or atleast which had been known but for a short time, and the names of whichhad not yet received the sanction of the public; and, secondly, when thenames which had been adopted, whether by the ancients or the moderns,appeared to us to express evidently false ideas, when they confoundedthe substances, to which they were applied, with others possessed ofdifferent, or perhaps opposite qualities. We made no scruple, in thiscase, of substituting other names in their room, and the greatest numberof these were borrowed from the Greek language. We[Pg xxvi] endeavoured to framethem in such a manner as to express the most general and the mostcharacteristic quality of the substances; and this was attended with theadditional advantage both of assisting the memory of beginners, who findit difficult to remember a new word which has no meaning, and ofaccustoming them early to admit no word without connecting with it somedeterminate idea.
To those bodies which are formed by the union of several simplesubstances we gave new names, compounded in such a manner as the natureof the substances directed; but, as the number of double combinations isalready very considerable, the only method by which we could avoidconfusion, was to divide them into classes. In the natural order ofideas, the name of the class or genus is that which expresses a qualitycommon to a great number of individuals: The name of the species, on thecontrary, expresses a quality peculiar to certain individuals only.
These distinctions are not, as some may imagine, merely metaphysical,but are established by Nature. "A child," says the Abbé de Condillac,[Pg xxvii]"is taught to give the nametree to the first one which is pointed outto him. The next one he sees presents the same idea, and he gives it thesame name. This he does likewise to a third and a fourth, till at lastthe wordtree, which he first applied to an individual, comes to beemployed by him as the name of a class or a genus, an abstract idea,which comprehends all trees in general. But, when he learns that alltrees serve not the same purpose, that they do not all produce the samekind of fruit, he will soon learn to distinguish them by specific andparticular names." This is the logic of all the sciences, and isnaturally applied to chemistry.
The acids, for example, are compounded of two substances, of the orderof those which we consider as simple; the one constitutes acidity, andis common to all acids, and, from this substance, the name of the classor the genus ought to be taken; the other is peculiar to each acid, anddistinguishes it from the rest, and from this substance is to be takenthe name of the species. But, in the greatest number of acids, the twoconstituent elements, the acidifying principle,[Pg xxviii] and that which itacidifies, may exist in different proportions, constituting all thepossible points of equilibrium or of saturation. This is the case in thesulphuric and the sulphurous acids; and these two states of the sameacid we have marked by varying the termination of the specific name.
Metallic substances which have been exposed to the joint action of theair and of fire, lose their metallic lustre, increase in weight, andassume an earthy appearance. In this state, like the acids, they arecompounded of a principle which is common to all, and one which ispeculiar to each. In the same way, therefore, we have thought proper toclass them under a generic name, derived from the common principle; forwhich purpose, we adopted the termoxyd; and we distinguish them fromeach other by the particular name of the metal to which each belongs.
Combustible substances, which in acids and metallic oxyds are a specificand particular principle, are capable of becoming, in their turn, commonprinciples of a great number of substances. The sulphurous combinationshave[Pg xxix] been long the only known ones in this kind. Now, however, we know,from the experiments of Messrs Vandermonde, Monge, and Berthollet, thatcharcoal may be combined with iron, and perhaps with several othermetals; and that, from this combination, according to the proportions,may be produced steel, plumbago, &c. We know likewise, from theexperiments of M. Pelletier, that phosphorus may be combined with agreat number of metallic substances. These different combinations wehave classed under generic names taken from the common substance, with atermination which marks this analogy, specifying them by another nametaken from that substance which is proper to each.
The nomenclature of bodies compounded of three simple substances wasattended with still greater difficulty, not only on account of theirnumber, but, particularly, because we cannot express the nature of theirconstituent principles without employing more compound names. In thebodies which form this class, such as the neutral salts, for instance,we had to consider, 1st, The acidifying principle, which is common tothem all; 2d, The acidifiable principle which constitutes their peculiaracid; 3d, The saline,[Pg xxx] earthy, or metallic basis, which determines theparticular species of salt. Here we derived the name of each class ofsalts from the name of the acidifiable principle common to all theindividuals of that class; and distinguished each species by the name ofthe saline, earthy, or metallic basis, which is peculiar to it.
A salt, though compounded of the same three principles, may,nevertheless, by the mere difference of their proportion, be in threedifferent states. The nomenclature we have adopted would have beendefective, had it not expressed these different states; and this weattained chiefly by changes of termination uniformly applied to the samestate of the different salts.
In short, we have advanced so far, that from the name alone may beinstantly found what the combustible substance is which enters into anycombination; whether that combustible substance be combined with theacidifying principle, and in what proportion; what is the state of theacid; with what basis it is united; whether the saturation be exact, orwhether the acid or the basis be in excess.[Pg xxxi]
It may be easily supposed that it was not possible to attain all thesedifferent objects without departing, in some instances, from establishedcustom, and adopting terms which at first sight will appear uncouth andbarbarous. But we considered that the ear is soon habituated to newwords, especially when they are connected with a general and rationalsystem. The names, besides, which were formerly employed, such aspowder of algaroth,salt of alembroth,pompholix,phagadenicwater,turbith mineral,colcathar, and many others, were neitherless barbarous nor less uncommon. It required a great deal of practice,and no small degree of memory, to recollect the substances to which theywere applied, much more to recollect the genus of combination to whichthey belonged. The names ofoil of tartar per deliquium,oil ofvitriol,butter of arsenic and of antimony,flowers of zinc, &c.were still more improper, because they suggested false ideas: For, inthe whole mineral kingdom, and particularly in the metallic class, thereexists no such thing as butters, oils, or flowers; and, in short, thesubstances to which they give these fallacious names, are nothing lessthan rank poisons.[Pg xxxii]
When we published our essay on the nomenclature of chemistry, we werereproached for having changed the language which was spoken by ourmasters, which they distinguished by their authority, and handed down tous. But those who reproach us on this account, have forgotten that itwas Bergman and Macquer themselves who urged us to make thisreformation. In a letter which the learned Professor of Upsal, M.Bergman, wrote, a short time before he died, to M. de Morveau, he bidshimspare no improper names; those who are learned, will always belearned, and those who are ignorant will thus learn sooner.
There is an objection to the work which I am going to present to thepublic, which is perhaps better founded, that I have given no account ofthe opinion of those who have gone before me; that I have stated only myown opinion, without examining that of others. By this I have beenprevented from doing that justice to my associates, and more especiallyto foreign chemists, which I wished to render them. But I beseech thereader to consider, that, if I had filled an elementary work with amultitude of quotations; if I had allowed myself to enter into[Pg xxxiii] longdissertations on the history of the science, and the works of those whohave studied it, I must have lost sight of the true object I had inview, and produced a work, the reading of which must have been extremelytiresome to beginners. It is not to the history of the science, or ofthe human mind, that we are to attend in an elementary treatise: Ouronly aim ought to be ease and perspicuity, and with the utmost care tokeep every thing out of view which might draw aside the attention of thestudent; it is a road which we should be continually rendering moresmooth, and from which we should endeavour to remove every obstaclewhich can occasion delay. The sciences, from their own nature, present asufficient number of difficulties, though we add not those which areforeign to them. But, besides this, chemists will easily perceive, that,in the first part of my work, I make very little use of any experimentsbut those which were made by myself: If at any time I have adopted,without acknowledgment, the experiments or the opinions of M.Berthollet, M. Fourcroy, M. de la Place, M. Monge, or, in general, ofany of those whose principles are the same with my own, it is owing tothis circumstance, that frequent intercourse, and the habit ofcommunicating our[Pg xxxiv] ideas, our observations, and our way of thinking toeach other, has established between us a sort of community of opinions,in which it is often difficult for every one to know his own.
The remarks I have made on the order which I thought myself obliged tofollow in the arrangement of proofs and ideas, are to be applied only tothe first part of this work. It is the only one which contains thegeneral sum of the doctrine I have adopted, and to which I wished togive a form completely elementary.
The second part is composed chiefly of tables of the nomenclature of theneutral salts. To these I have only added general explanations, theobject of which was to point out the most simple processes for obtainingthe different kinds of known acids. This part contains nothing which Ican call my own, and presents only a very short abridgment of theresults of these processes, extracted from the works of differentauthors.
In the third part, I have given a description, in detail, of all theoperations connected with modern chemistry. I have long thought that a[Pg xxxv]work of this kind was much wanted, and I am convinced it will not bewithout use. The method of performing experiments, and particularlythose of modern chemistry, is not so generally known as it ought to be;and had I, in the different memoirs which I have presented to theAcademy, been more particular in the detail of the manipulations of myexperiments, it is probable I should have made myself better understood,and the science might have made a more rapid progress. The order of thedifferent matters contained in this third part appeared to me to bealmost arbitrary; and the only one I have observed was to classtogether, in each of the chapters of which it is composed, thoseoperations which are most connected with one another. I need hardlymention that this part could not be borrowed from any other work, andthat, in the principal articles it contains, I could not deriveassistance from any thing but the experiments which I have made myself.
I shall conclude this preface by transcribing, literally, someobservations of the Abbé de Condillac, which I think describe, with agood deal of truth, the state of chemistry at a period not far distantfrom our own. These observations[Pg xxxvi] were made on a different subject; butthey will not, on this account, have less force, if the application ofthem be thought just.
'Instead of applying observation to the things we wished to know, wehave chosen rather to imagine them. Advancing from one ill foundedsupposition to another, we have at last bewildered ourselves amidst amultitude of errors. These errors becoming prejudices, are, of course,adopted as principles, and we thus bewilder ourselves more and more. Themethod, too, by which we conduct our reasonings is as absurd; we abusewords which we do not understand, and call this the art of reasoning.When matters have been brought this length, when errors have been thusaccumulated, there is but one remedy by which order can be restored tothe faculty of thinking; this is, to forget all that we have learned, totrace back our ideas to their source, to follow the train in which theyrise, and, as my Lord Bacon says, to frame the human understanding anew.
'This remedy becomes the more difficult in proportion as we thinkourselves more learned.[Pg xxxvii] Might it not be thought that works whichtreated of the sciences with the utmost perspicuity, with greatprecision and order, must be understood by every body? The fact is,those who have never studied any thing will understand them better thanthose who have studied a great deal, and especially than those who havewritten a great deal.'
At the end of the fifth chapter, the Abbé de Condillac adds: 'But, afterall, the sciences have made progress, because philosophers have appliedthemselves with more attention to observe, and have communicated totheir language that precision and accuracy which they have employed intheir observations: In correcting their language they reason better.'
PART FIRST.
Of the Formation and Decomposition ofAëriform Fluids,
—of the Combustionof Simple Bodies, and the Formationof Acids,Page 1
CHAP. I.—Of the Combinations of Caloric, andthe Formation of Elastic Aëriform Fluids orGasses,ibid.
CHAP. II.—General Views relative to the Formationand Composition of our Atmosphere,26
CHAP. III.—Analysis of Atmospheric Air, and itsDivision into two Elastic Fluids;
one fit forRespiration, the other incapable of being respired,32
CHAP. IV.—Nomenclature of the several constituentParts of Atmospheric Air,48
CHAP. V.—Of the Decomposition of OxygenGas by Sulphur,
Phosphorus, and Charcoal, and[Pg xl]of the Formation of Acids in general,54
CHAP. VI.—Of the Nomenclature of Acids in general,and particularly of those drawn fromNitre and Sea Salt,66
CHAP. VII.—Of the Decomposition of OxygenGas
by means of Metals, and the Formation ofMetallic Oxyds,78
CHAP. VIII.—Of the Radical Principle of Water,and of its Decomposition by Charcoal andIron,83
CHAP. IX.—Of the Quantities of Caloric disengagedfrom different Species of Combustion,97
Combustion of Phosphorus,100
SECT. I.—Combustion of Charcoal,101
SECT. II.—Combustion of Hydrogen Gas,102
SECT. III.—Formation of Nitric Acid,102
SECT. IV.—Combustion of Wax,105
SECT. V.—Combustion of Olive Oil,106
CHAP. X.—Of the Combustion of CombustibleSubstances with each other,109
CHAP. XI.—Observations upon Oxyds and Acidswith several Bases,
and upon the Compositionof Animal and Vegetable Substances,115
CHAP. XII.—Of the Decomposition of Vegetableand Animal Substances by the Action of Fire,123
CHAP. XIII.—Of the Decomposition of VegetableOxyds by the Vinous Fermentation,129
CHAP. XIV.—Of the Putrefactive Fermentation,141
CHAP. XV.—Of the Acetous Fermentation,146
CHAP. XVI.—Of the Formation of Neutral Salts,and of their Bases,149
[Pg xli]
SECT. I.—Of Potash,151
SECT. II.—Of Soda,155
SECT. III.—Of Ammoniac,156
SECT. IV.—Of Lime, Magnesia, Barytes, and Argill,157
SECT. V.—Of Metallic Bodies,159
CHAP. XVII.—Continuation of the Observationsupon Salifiable Bases, and the Formationof Neutral Salts,161
PART II.
Of the Combinations of Acids with SalifiableBases, and of the Formationof Neutral Salts,175
INTRODUCTION,ibid.
TABLE of Simple Substances,175
SECT. I.—Observations upon simple Substances,176
TABLE of Compound Oxydable and AcidifiableBases,179
SECT. II.—Observations upon Compound Radicals,180
SECT. III.—Observations upon the Combinationsof Light and Caloric with different Substances,182
[Pg xlii]TABLE of the Combinations of Oxygen with theSimple Substances, to face185
SECT. IV.—Observations upon these Combinations,185
TABLE of the Combinations of Oxygen with CompoundRadicals,190
SECT. V.—Observations upon these Combinations,191
TABLE of the Combinations of Azote with theSimple Substances,194
SECT VI.—Observations upon these Combinationsof Azote,195
TABLE of the Combinations of Hydrogen withSimple Substances,198
SECT. VII.—Observations upon Hydrogen, and itsCombinations,199
TABLE of the Binary Combinations of Sulphurwith the Simple Substances,202
SECT. VIII.—Observations upon Sulphur, and itsCombinations,203
TABLE of the Combinations of Phosphorus withSimple Substances,204
SECT. IX.—Observations upon Phosphorus and itsCombinations,205
TABLE of the Binary Combinations of Charcoal,207
SECT. X.—Observations upon Charcoal, and itsCombinations,208
SECT. XI.—Observations upon the Muriatic, Fluoric,and Boracic Radicals, and their Combinations,209
[Pg xliii]SECT. XII.—Observations upon the Combinationsof Metals with each other,219
TABLE of the Combinations of Azote, in the Stateof Nitrous Acid, with the Salifiable Bases,212
TABLE of the Combinations of Azote, in the Stateof Nitric Acid, with the Salifiable Bases,213
SECT. XIII.—Observations upon Nitrous and NitricAcids, and their Combinations with SalifiableBases,214
TABLE of the Combinations of Sulphuric Acidwith the Salifiable Bases,218
SECT. XIV.—Observations upon Sulphuric Acid,and its Combinations,219
TABLE of the Combinations of Sulphurous Acid,222
SECT. XV.—Observations upon Sulphurous Acid,and its Combinations with Salifiable Bases,223
TABLE of the Combinations of Phosphorous andPhosphoric Acids,225
SECT. XVI.—Observations upon Phosphorous andPhosphoric Acids, and their Combinationswith Salifiable Bases,226
TABLE of the Combinations of Carbonic Acid,228
SECT. XVII.—Observations upon Carbonic Acid,and its Combinations with Salifiable Bases,229
TABLE of the Combinations of Muriatic Acid,231
TABLE of the Combinations of Oxygenated Muriatic Acid,232
[Pg xliv]SECT. XVIII.—Observations upon Muriatic andOxygenated Muriatic Acid,
and their Combinationswith Salifiable Bases,233
TABLE of the Combinations of Nitro-Muriatic Acid,236
SECT. XIX.—Observations upon Nitro-muriaticAcid, and its Combinations with SalifiableBases,237
TABLE of the Combinations of Fluoric Acid,239
SECT. XX.—Observations upon Fluoric Acid, andits Combinations with Salifiable Bases,240
TABLE of the Combinations of Boracic Acid,242
SECT. XXI.—Observations upon Boracic Acid,and its Combinations with Salifiable Bases,243
TABLE of the Combinations of Arseniac Acid,246
SECT. XXII.—Observations upon Arseniac Acid,and its Combinations with Salifiable Bases,247
SECT. XXIII.—Observations upon Molibdic Acid,and its Combinations with Salifiable Bases,249
SECT. XXIV.—Observations upon Tungstic Acid,and its Combinations with Salifiable Bases,
anda Table of these in the order of their Affinity,251
TABLE of the Combinations of Tartarous Acid,253
SECT. XXV.—Observations upon Tartarous Acid,and its Combinations with Salifiable Bases,254
SECT. XXVI.—Observations upon Mallic Acid,and its Combinations with Salifiable Bases,256
TABLE of the Combinations of Citric Acid,258
SECT. XXVII.—Observations upon Citric Acid,and its Combinations with Salifiable Bases,259
[Pg xlv]TABLE of the Combinations of Pyro-lignous Acid,260
SECT. XXVIII.—Observations upon Pyro-lignousAcid, and its Combinations with Salifiable Bases,261
SECT. XXIX.—Observations upon Pyro-tartarousAcid, and its Combinations with SalifiableBases,ibid.
TABLE of the Combinations of Pyro-mucous Acid,263
SECT. XXX.—Observations upon Pyro-mucousAcid, and its Combinations with Salifiable Bases,264
TABLE of the Combinations of Oxalic Acid,265
SECT. XXXI.—Observations upon Oxalic Acid,and its Combinations with Salifiable Bases,266
TABLE of the Combinations of Acetous Acid, toface267
SECT. XXXII.—Observations upon Acetous Acid,and its Combinations with the Salifiable Bases,267
TABLE of the Combinations of Acetic Acid,271
SECT. XXXIII.—Observations upon Acetic Acid,and its Combinations with Salifiable Bases,272
TABLE of the Combinations of Succinic Acid,273
SECT. XXXIV.—Observations upon Succinic Acid,and its Combinations with Salifiable Bases,274
SECT. XXXV.—Observations upon Benzoic Acid,and its Combinations with Salifiable Bases,275
SECT. XXXVI.—Observations upon CamphoricAcid, and its Combinations with Salifiable[Pg xlvi]Bases,276
SECT. XXXVII.—Observations upon Gallic Acid,and its Combinations with Salifiable Bases,277
SECT. XXXVIII.—Observations upon Lactic Acid,and its Combinations with Salifiable Bases,278
TABLE of the Combinations of Saccholactic Acid,280
SECT. XXXIX.—Observations upon SaccholacticAcid, and its Combination with Salifiable Bases,281
TABLE of the Combinations of Formic Acid,282
SECT. XL.—Observations upon Formic Acid, andits Combinations with the Salifiable Bases,283
SECT. XLI.—Observations upon the Bombic Acid,and its Combinations with the Salifiable Bases,284
TABLE of the Combinations of the Sebacic Acid,285
SECT. XLII.—Observations upon the Sebacic Acid,and its Combinations with the Salifiable Bases,286
SECT. XLIII.—Observations upon the Lithic Acid,and its Combinations with the Salifiable Bases,287
TABLE of the Combinations of the Prussic Acid,288
SECT. XLIV.—Observations upon the Prussic Acid,and its Combinations with the Salifiable Bases,289
PART III.
[Pg xlvii]Description of the Instruments and Operationsof Chemistry,291
INTRODUCTION,291
CHAP. I.—Of the Instruments necessary for determining
the Absolute and Specific Gravities ofSolid and Liquid Bodies,295
CHAP. II.—Of Gazometry, or the Measurementof the Weight and Volume of Aëriform Substances,304
SECT. I.—Of the Pneumato-chemical Apparatus,ibid.
SECT. II.—Of the Gazometer,308
SECT. III.—Some other methods for Measuringthe Volume of Gasses,319
SECT. IV.—Of the method of Separating the differentGasses from each other,323
SECT. V.—Of the necessary Corrections of the Volumeof Gasses,
according to the Pressure ofthe Atmosphere,328
SECT. VI.—Of the Correction relative to the Degreesof the Thermometer,335
SECT. VII.—Example for Calculating the Corrections
relative to the Variations of Pressure andTemperature,337
SECT. VIII.—Method of determining the Weightof the different Gasses,340
CHAP. III.—Description of the Calorimeter, orApparatus for measuring Caloric,343
CHAP. IV.—Of the Mechanical Operations forDivision of Bodies,357
[Pg xlviii]SECT. I.—Of Trituration, Levigation, and Pulverization,ibid.
SECT. II.—Of Sifting and Washing PowderedSubstances,361
SECT. III.—Of Filtration,363
SECT. IV.—Of Decantation,365
CHAP. V.—Of Chemical means for Separating theParticles of Bodies
from each other withoutDecomposition, and for Uniting them again,367
SECT. I.—Of the Solution of Salts,368
SECT. II.—Of Lixiviation,373
SECT. III.—Of Evaporation,375
SECT. IV.—Of Cristallization,379
SECT. V.—Of Simple Distillation,384
SECT. VI.—Of Sublimation,388
CHAP. VI.—Of Pneumato-chemical Distillations,Metallic Dissolutions,
and some other operationswhich require very complicated instruments,390
SECT. I.—Of Compound and Pneumato-chemicalDistillations,ibid.
SECT. II.—Of Metallic Dissolutions,398
SECT. III.—Apparatus necessary in Experimentsupon Vinous and Putrefactive Fermentations,401
SECT. IV.—Apparatus for the Decomposition ofWater,404
CHAP. VII.—Of the Composition and Use ofLutes,407
CHAP. VIII.—Of Operations upon Combustionand Deflagration,414
SECT. I.—Of Combustion in general,ibid.
SECT. II.—Of the Combustion of Phosphorus,418
[Pg xlix]SECT. III.—Of the Combustion of Charcoal,422
SECT. IV.—Of the Combustion of Oils,426
SECT. V.—Of the Combustion of Alkohol,433
SECT. VI.—Of the Combustion of Ether,435
SECT. VII.—Of the Combustion of HydrogenGas, and the Formation of Water,437
SECT. VIII.—Of the Oxydation of Metals,441
CHAP. IX.—Of Deflagration,452
CHAP. X.—Of the Instruments necessary for Operatingupon Bodies in very high Temperatures,460
SECT. I.—Of Fusion,ibid.
SECT. II.—Of Furnaces,462
SECT. III.—Of increasing the Action of Fire, byusing Oxygen Gas instead of Atmospheric Air,474
APPENDIX.
No. I.—Table for Converting Lines, or TwelfthParts of an Inch,
and Fractions of Lines, intoDecimal Fractions of the Inch,481
No. II.—Table for Converting the ObservedHeighth of Water in the Jars of the Pneumato-Chemical
Apparatus, expressed in Inches andDecimals, into Corresponding Heighths of Mercury,482
No. III.—Table for Converting the OunceMeasures used
by Dr Priestley into French andEnglish Cubical Inches,483
[Pg l]No. IV.—Table for Reducing the Degrees of
Reaumeur's Thermometer into its correspondingDegrees of Fahrenheit's Scale,484
No. V.—Additional.—Rules for ConvertingFrench Weights
and Measures into correspondentEnglish Denominations,485
No. VI.—Table of the Weights of the differentGasses, at 28 French inches,
or 29.84 Englishinches barometrical pressure, and at 10° (54.5°)of temperature,
expressed in English measureand English Troy weight,490
No. VII.—Tables of the Specific Gravities ofdifferent bodies,491
No. VIII.—Additional.—Rules for Calculatingthe Absolute Gravity in English TroyWeight of a
Cubic Foot and Inch, EnglishMeasure, of any Substance whose Specific Gravityis known,505
No. IX.—Tables for Converting Ounces, Drams,and Grains, Troy, into
Decimals of the TroyPound of 12 Ounces, and for Converting Decimalsof the Pound Troy
into Ounces, &c.508
No. X.—Table of the English Cubical Inches andDecimals corresponding to a determinate Troy
Weight of Distilled Water at the Temperatureof 55°, calculated from Everard's experiment,511
Of the Formation and Decomposition of Aëriform Fluids—of theCombustion of Simple Bodies—and the Formation of Acids.
That every body, whether solid or fluid, is augmented in all itsdimensions by any increase of its sensible heat, was long ago fullyestablished as a physical axiom, or universal proposition, by thecelebrated Boerhaave. Such facts as have been adduced for controvertingthe[Pg 2] generality of this principle offer only fallacious results, or, atleast, such as are so complicated with foreign circumstances as tomislead the judgment: But, when we separately consider the effects, soas to deduce each from the cause to which they separately belong, it iseasy to perceive that the separation of particles by heat is a constantand general law of nature.
When we have heated a solid body to a certain degree, and have therebycaused its particles to separate from each other, if we allow the bodyto cool, its particles again approach each other in the same proportionin which they were separated by the increased temperature; the bodyreturns through the same degrees of expansion which it before extendedthrough; and, if it be brought back to the same temperature from whichwe set out at the commencement of the experiment, it recovers exactlythe same dimensions which it formerly occupied. But, as we are stillvery far from being able to arrive at the degree of absolute cold, ordeprivation of all heat, being unacquainted with any degree of coldnesswhich we cannot suppose capable of still farther augmentation, itfollows, that we are still incapable of causing the ultimate particlesof bodies to approach each other as near as is possible; and,consequently, that the particles of all bodies do not touch each otherin any state hitherto known, which, tho'[Pg 3] a very singular conclusion, isyet impossible to be denied.
It is supposed, that, since the particles of bodies are thus continuallyimpelled by heat to separate from each other, they would have noconnection between themselves; and, of consequence, that there could beno solidity in nature, unless they were held together by some otherpower which tends to unite them, and, so to speak, to chain themtogether; which power, whatever be its cause, or manner of operation, wename Attraction.
Thus the particles of all bodies may be considered as subjected to theaction of two opposite powers, the one repulsive, the other attractive,between which they remain in equilibrio. So long as the attractive forceremains stronger, the body must continue in a state of solidity; but if,on the contrary, heat has so far removed these particles from eachother, as to place them beyond the sphere of attraction, they lose theadhesion they before had with each other, and the body ceases to besolid.
Water gives us a regular and constant example of these facts; whilstbelow Zero[2] of the French thermometer, or 32° of Fahrenheit,[Pg 4] itremains solid, and is called ice. Above that degree of temperature, itsparticles being no longer held together by reciprocal attraction, itbecomes liquid; and, when we raise its temperature above 80°, (212°) itsparticles, giving way to the repulsion caused by the heat, assume thestate of vapour or gas, and the water is changed into an aëriform fluid.
The same may be affirmed of all bodies in nature: They are either solidor liquid, or in the state of elastic aëriform vapour, according to theproportion which takes place between the attractive force inherent intheir particles, and the repulsive power of the heat acting upon these;or, what amounts to the same thing, in proportion to the degree of heatto which they are exposed.
It is difficult to comprehend these phenomena, without admitting them asthe effects of a real and material substance, or very subtile fluid,which, insinuating itself between the particles of bodies, separatesthem from each other; and, even allowing the existence of this fluid tobe hypothetical, we shall see in the sequel, that it explains thephenomena of nature in a very satisfactory manner.
This substance, whatever it is, being the cause of heat, or, in otherwords, the sensation which we callwarmth being caused by theaccumulation of this substance, we cannot, in strict language,[Pg 5]distinguish it by the termheat; because the same name would then veryimproperly express both cause and effect. For this reason, in the memoirwhich I published in 1777[3], I gave it the names ofigneous fluid andmatter of heat. And, since that time, in the work[4] published by Mrde Morveau, Mr Berthollet, Mr de Fourcroy, and myself, upon thereformation of chemical nomenclature, we thought it necessary to banishall periphrastic expressions, which both lengthen physical language, andrender it more tedious and less distinct, and which even frequently doesnot convey sufficiently just ideas of the subject intended. Wherefore,we have distinguished the cause of heat, or that exquisitely elasticfluid which produces it, by the term ofcaloric. Besides, that thisexpression fulfils our object in the system which we have adopted, itpossesses this farther advantage, that it accords with every species ofopinion, since, strictly speaking, we are not obliged to suppose this tobe a real substance; it being sufficient, as will more clearly appear inthe sequel of this work, that it be considered as the repulsive cause,whatever that may be, which separates the particles of matter from eachother; so that[Pg 6] we are still at liberty to investigate its effects in anabstract and mathematical manner.
In the present state of our knowledge, we are unable to determinewhether light be a modification of caloric, or if caloric be, on thecontrary, a modification of light. This, however, is indisputable, that,in a system where only decided facts are admissible, and where we avoid,as far as possible, to suppose any thing to be that is not really knownto exist, we ought provisionally to distinguish, by distinct terms, suchthings as are known to produce different effects. We thereforedistinguish light from caloric; though we do not therefore deny thatthese have certain qualities in common, and that, in certaincircumstances, they combine with other bodies almost in the same manner,and produce, in part, the same effects.
What I have already said may suffice to determine the idea affixed tothe wordcaloric; but there remains a more difficult attempt, whichis, to give a just conception of the manner in which caloric acts uponother bodies. Since this subtile matter penetrates through the pores ofall known substances; since there are no vessels through which it cannotescape, and, consequently, as there are none which are capable ofretaining it, we can only come at the knowledge of its properties byeffects which are fleeting, and difficultly ascertainable. It is in[Pg 7]these things which we neither see nor feel, that it is especiallynecessary to guard against the extravagancy of our imagination, whichforever inclines to step beyond the bounds of truth, and is verydifficultly restrained within the narrow line of facts.
We have already seen, that the same body becomes solid, or fluid, oraëriform, according to the quantity of caloric by which it ispenetrated; or, to speak more strictly, according as the repulsive forceexerted by the caloric is equal to, stronger, or weaker, than theattraction of the particles of the body it acts upon.
But, if these two powers only existed, bodies would become liquid at anindivisible degree of the thermometer, and would almost instantaneouslypass from the solid state of aggregation to that of aëriform elasticity.Thus water, for instance, at the very moment when it ceases to be ice,would begin to boil, and would be transformed into an aëriform fluid,having its particles scattered indefinitely through the surroundingspace. That this does not happen, must depend upon the action of somethird power. The pressure of the atmosphere prevents this separation,and causes the water to remain in the liquid state till it be raised to80° of temperature (212°) above zero of the French thermometer, thequantity of caloric which it receives in the lowest temperature beinginsufficient[Pg 8] to overcome the pressure of the atmosphere.
Whence it appears that, without this atmospheric pressure, we should nothave any permanent liquid, and should only be able to see bodies in thatstate of existence in the very instant of melting, as the smallestadditional caloric would instantly separate their particles, anddissipate them through the surrounding medium. Besides, without thisatmospheric pressure, we should not even have any aëriform fluids,strictly speaking, because the moment the force of attraction isovercome by the repulsive power of the caloric, the particles wouldseparate themselves indefinitely, having nothing to give limits to theirexpansion, unless their own gravity might collect them together, so asto form an atmosphere.
Simple reflection upon the most common experiments is sufficient toevince the truth of these positions. They are more particularly provedby the following experiment, which I published in the Memoirs of theFrench Academy for 1777, p. 426.
Having filled with sulphuric ether[5] a small narrow glass vessel, A,(Plate VII. Fig. 17.), standing[Pg 9] upon its stalk P, the vessel, which isfrom twelve to fifteen lines diameter, is to be covered by a wetbladder, tied round its neck with several turns of strong thread; forgreater security, fix a second bladder over the first. The vessel shouldbe filled in such a manner with the ether, as not to leave the smallestportion of air between the liquor and the bladder. It is now to beplaced under the recipient BCD of an air-pump, of which the upper part Bought to be fitted with a leathern lid, through which passes a wire EF,having its point F very sharp; and in the same receiver there ought tobe placed the barometer GH. The whole being thus disposed, let therecipient be exhausted, and then, by pushing down the wire EF, we make ahole in the bladder. Immediately the ether begins to boil with greatviolence, and is changed into an elastic aëriform fluid, which fills thereceiver. If the quantity of ether be sufficient to leave a few drops inthe phial after the evaporation is finished, the elastic fluid producedwill sustain the mercury in the barometer attached to the air-pump, ateight or ten inches in winter, and from[Pg 10] twenty to twenty-five insummer[6]. To render this experiment more complete, we may introduce asmall thermometer into the phial A, containing the ether, which willdescend considerably during the evaporation.
The only effect produced in this experiment is, the taking away theweight of the atmosphere, which, in its ordinary state, presses on thesurface of the ether; and the effects resulting from this removalevidently prove, that, in the ordinary temperature of the earth, etherwould always exist in an aëriform state, but for the pressure of theatmosphere, and that the passing of the ether from the liquid to theaëriform state is accompanied by a considerable lessening of heat;because, during the evaporation, a part of the caloric, which was beforein a free state, or at least in equilibrio in the surrounding bodies,combines with the ether, and causes it to assume the aëriform state.
The same experiment succeeds with all evaporable fluids, such asalkohol, water, and even mercury; with this difference, that theatmosphere formed in the receiver by alkohol only[Pg 11] supports the attachedbarometer about one inch in winter, and about four or five inches insummer; that formed by water, in the same situation, raises the mercuryonly a few lines, and that by quicksilver but a few fractions of a line.There is therefore less fluid evaporated from alkohol than from ether,less from water than from alkohol, and still less from mercury than fromeither; consequently there is less caloric employed, and less coldproduced, which quadrates exactly with the results of these experiments.
Another species of experiment proves very evidently that the aëriformstate is a modification of bodies dependent on the degree oftemperature, and on the pressure which these bodies undergo. In a Memoirread by Mr de la Place and me to the Academy in 1777, which has not beenprinted, we have shown, that, when ether is subjected to a pressureequal to twenty-eight inches of the barometer, or about the mediumpressure of the atmosphere, it boils at the temperature of about 32°(104°), or 33° (106.25°), of the thermometer. Mr de Luc, who has madesimilar experiments with spirit of wine, finds it boils at 67°(182.75°). And all the world knows that water boils at 80° (212°). Now,boiling being only the evaporation of a liquid, or the moment of itspassing from the fluid to the aëriform state, it is evident that, if wekeep[Pg 12] ether continually at the temperature of 33° (106.25°), and underthe common pressure of the atmosphere, we shall have it always in anelastic aëriform state; and that the same thing will happen with alkoholwhen above 67° (182.75°), and with water when above 80° (212°); allwhich are perfectly conformable to the following experiment[7].
I filled a large vessel ABCD (Plate VII. Fig. 16.) with water, at 35°(110.75°), or 36° (113°); I suppose the vessel transparent, that we maysee what takes place in the experiment; and we can easily hold the handsin water at that temperature without inconvenience. Into it I plungedsome narrow necked bottles F, G, which were filled with the water, afterwhich they were turned up, so as to rest on their mouths on the bottomof the vessel. Having next put some ether into a very small matrass,with its necka b c, twice bent as in the Plate, I plunged thismatrass into the water, so as to have its neck inserted into the mouthof one of the bottles F. Immediately upon feeling the effects of theheat communicated to it by the water in the vessel ABCD it began toboil; and the caloric entering into combination with it, changed it intoelastic aëriform fluid, with which I filled several bottlessuccessively, F, G, &c.
This is not the place to enter upon the examination of the nature andproperties of this aëriform fluid, which is extremely inflammable; but,confining myself to the object at present in view, without anticipatingcircumstances, which I am not to suppose the reader to know, I shallonly observe, that the ether, from this experiment, is almost onlycapable of existing in the aëriform state in our world; for, if theweight of our atmosphere was only equal to between 20 and 24 inches ofthe barometer, instead of 28 inches, we should never be able to obtainether in the liquid state, at least in summer; and the formation ofether would consequently be impossible upon mountains of a moderatedegree of elevation, as it would be converted into gas immediately uponbeing produced, unless we employed recipients of extraordinary strength,together with refrigeration and compression. And, lastly, thetemperature of the blood being nearly that at which ether passes fromthe liquid to the aëriform state, it must evaporate in the primae viae,and consequently it is very probable the medical properties of thisfluid depend chiefly upon its mechanical effect.
These experiments succeed better with nitrous ether, because itevaporates in a lower temperature than sulphuric ether. It is moredifficult to obtain alkohol in the aëriform state; because, as itrequires 67° (182.75°) to reduce it to vapour,[Pg 14] the water of the bathmust be almost boiling, and consequently it is impossible to plunge thehands into it at that temperature.
It is evident that, if water were used in the foregoing experiment, itwould be changed into gas, when exposed to a temperature superior tothat at which it boils. Although thoroughly convinced of this, Mr de laPlace and myself judged it necessary to confirm it by the followingdirect experiment. We filled a glass jar A, (Plate VII. Fig. 5.) withmercury, and placed it with its mouth downwards in a dish B, likewisefilled with mercury, and having introduced about two gross of water intothe jar, which rose to the top of the mercury at CD; we then plunged thewhole apparatus into an iron boiler EFGH, full of boiling sea-water ofthe temperature of 85° (123.25°), placed upon the furnace GHIK.Immediately upon the water over the mercury attaining the temperature of80° (212°), it began to boil; and, instead of only filling the smallspace ACD, it was converted into an aëriform fluid, which filled thewhole jar; the mercury even descended below the surface of that in thedish B; and the jar must have been overturned, if it had not been verythick and heavy, and fixed to the dish by means of iron-wire.Immediately after withdrawing the apparatus from the boiler, the vapourin the jar began to condense, and the[Pg 15] mercury rose to its formerstation; but it returned again to the aëriform state a few seconds afterreplacing the apparatus in the boiler.
We have thus a certain number of substances, which are convertible intoelastic aëriform fluids by degrees of temperature, not much superior tothat of our atmosphere. We shall afterwards find that there are severalothers which undergo the same change in similar circumstances, such asmuriatic or marine acid, ammoniac or volatile alkali, the carbonic acidor fixed air, the sulphurous acid, &c. All of these are permanentlyelastic in or about the mean temperature of the atmosphere, and underits common pressure.
All these facts, which could be easily multiplied if necessary, give mefull right to assume, as a general principle, that almost every body innature is susceptible of three several states of existence, solid,liquid, and aëriform, and that these three states of existence dependupon the quantity of caloric combined with the body. Henceforwards Ishall express these elastic aëriform fluids by the generic termgas;and in each species of gas I shall distinguish between the caloric,which in some measure serves the purpose of a solvent, and thesubstance, which in combination with the caloric, forms the base of thegas.[Pg 16]
To these bases of the different gases, which are hitherto but littleknown, we have been obliged to assign names; these I shall point out inChap. IV. of this work, when I have previously given an account of thephenomena attendant upon the heating and cooling of bodies, and when Ihave established precise ideas concerning the composition of ouratmosphere.
We have already shown, that the particles of every substance in natureexist in a certain state of equilibrium, between that attraction whichtends to unite and keep the particles together, and the effects of thecaloric which tends to separate them. Hence the caloric not onlysurrounds the particles of all bodies on every side, but fills up everyinterval which the particles of bodies leave between each other. We mayform an idea of this, by supposing a vessel filled with small sphericalleaden bullets, into which a quantity of fine sand is poured, which,insinuating into the intervals between the bullets, will fill up everyvoid. The balls, in this comparison, are to the sand which surroundsthem exactly in the same situation as the particles of bodies are withrespect to the caloric; with this difference only, that the balls aresupposed to touch each other, whereas the particles of bodies are not incontact, being retained at a small distance from each other, by thecaloric.[Pg 17]
If, instead of spherical balls, we substitute solid bodies of ahexahedral, octohedral, or any other regular figure, the capacity of theintervals between them will be lessened, and consequently will no longercontain the same quantity of sand. The same thing takes place, withrespect to natural bodies; the intervals left between their particlesare not of equal capacity, but vary in consequence of the differentfigures and magnitude of their particles, and of the distance at whichthese particles are maintained, according to the existing proportionbetween their inherent attraction, and the repulsive force exerted uponthem by the caloric.
In this manner we must understand the following expression, introducedby the English philosophers, who have given us the first precise ideasupon this subject;the capacity of bodies for containing the matter ofheat. As comparisons with sensible objects are of great use inassisting us to form distinct notions of abstract ideas, we shallendeavour to illustrate this, by instancing the phenomena which takeplace between water and bodies which are wetted and penetrated by it,with a few reflections.
If we immerge equal pieces of different kinds of wood, suppose cubes ofone foot each, into water, the fluid gradually insinuates itself intotheir pores, and the pieces of wood are augmented both in weight andmagnitude: But[Pg 18] each species of wood will imbibe a different quantity ofwater; the lighter and more porous woods will admit a larger, thecompact and closer grained will admit of a lesser quantity; for theproportional quantities of water imbibed by the pieces will depend uponthe nature of the constituent particles of the wood, and upon thegreater or lesser affinity subsisting between them and water. Veryresinous wood, for instance, though it may be at the same time veryporous, will admit but little water. We may therefore say, that thedifferent kinds of wood possess different capacities for receivingwater; we may even determine, by means of the augmentation of theirweights, what quantity of water they have actually absorbed; but, as weare ignorant how much water they contained, previous to immersion, wecannot determine the absolute quantity they contain, after being takenout of the water.
The same circumstances undoubtedly take place, with bodies that areimmersed in caloric; taking into consideration, however, that water isan incompressible fluid, whereas caloric is, on the contrary, endowedwith very great elasticity; or, in other words, the particles of calorichave a great tendency to separate from each other, when forced by anyother power to approach; this difference must of necessity occasion[Pg 19]very considerable diversities in the results of experiments made uponthese two substances.
Having established these clear and simple propositions, it will be veryeasy to explain the ideas which ought to be affixed to the followingexpressions, which are by no means synonimous, but possess each a strictand determinate meaning, as in the following definitions:
Free caloric, is that which is not combined in any manner with anyother body. But, as we live in a system to which caloric has a verystrong adhesion, it follows that we are never able to obtain it in thestate of absolute freedom.
Combined caloric, is that which is fixed in bodies by affinity orelective attraction, so as to form part of the substance of the body,even part of its solidity.
By the expressionspecific caloric of bodies, we understand therespective quantities of caloric requisite for raising a number ofbodies of the same weight to an equal degree of temperature. Thisproportional quantity of caloric depends upon the distance between theconstituent particles of bodies, and their greater or lesser degrees ofcohesion; and this distance, or rather the space or void resulting fromit, is, as I have already observed, called thecapacity of bodies forcontaining caloric.[Pg 20]
Heat, considered as a sensation, or, in other words, sensible heat, isonly the effect produced upon our sentient organs, by the motion orpassage of caloric, disengaged from the surrounding bodies. In general,we receive impressions only in consequence of motion, and we mightestablish it as an axiom,That,without motion, there is no sensation.This general principle applies very accurately to the sensations of heatand cold: When we touch a cold body, the caloric which always tends tobecome in equilibrio in all bodies, passes from our hand into the bodywe touch, which gives us the feeling or sensation of cold. The directcontrary happens, when we touch a warm body, the caloric then passingfrom the body into our hand, produces the sensation of heat. If the handand the body touched be of the same temperature, or very nearly so, wereceive no impression, either of heat or cold, because there is nomotion or passage of caloric; and thus no sensation can take place,without some correspondent motion to occasion it.
When the thermometer rises, it shows, that free caloric is entering intothe surrounding bodies: The thermometer, which is one of these, receivesits share in proportion to its mass, and to the capacity which itpossesses for containing caloric. The change therefore which takes placeupon the thermometer, only announces a[Pg 21] change of place of the caloricin those bodies, of which the thermometer forms one part; it onlyindicates the portion of caloric received, without being a measure ofthe whole quantity disengaged, displaced, or absorbed.
The most simple and most exact method for determining this latter point,is that described by Mr de la Place, in the Memoirs of the Academy, No.1780, p. 364; a summary explanation of which will be found towards theconclusion of this work. This method consists in placing a body, or acombination of bodies, from which caloric is disengaging, in the midstof a hollow sphere of ice; and the quantity of ice melted becomes anexact measure of the quantity of caloric disengaged. It is possible, bymeans of the apparatus which we have caused to be constructed upon thisplan, to determine, not as has been pretended, the capacity of bodiesfor containing heat, but the ratio of the increase or diminution ofcapacity produced by determinate degrees of temperature. It is easy withthe same apparatus, by means of divers combinations of experiments, todetermine the quantity of caloric requisite for converting solidsubstances into liquids, and liquids into elastic aëriform fluids; and,vice versa, what quantity of caloric escapes from elastic vapours inchanging to liquids, and what quantity escapes from liquids during theirconversion into solids. Perhaps,[Pg 22] when experiments have been made withsufficient accuracy, we may one day be able to determine theproportional quantity of caloric, necessary for producing the severalspecies of gasses. I shall hereafter, in a separate chapter, give anaccount of the principal results of such experiments as have been madeupon this head.
It remains, before finishing this article, to say a few words relativeto the cause of the elasticity of gasses, and of fluids in the state ofvapour. It is by no means difficult to perceive that this elasticitydepends upon that of caloric, which seems to be the most eminentlyelastic body in nature. Nothing is more readily conceived, than that onebody should become elastic by entering into combination with anotherbody possessed of that quality. We must allow that this is only anexplanation of elasticity, by an assumption of elasticity, and that wethus only remove the difficulty one step farther, and that the nature ofelasticity, and the reason for caloric being elastic, remains stillunexplained. Elasticity in the abstract is nothing more than thatquality of the particles of bodies by which they recede from each otherwhen forced together. This tendency in the particles of caloric toseparate, takes place even at considerable distances. We shall besatisfied of this, when we consider that air is susceptible ofundergoing great compression, which supposes that its particles[Pg 23] werepreviously very distant from each other; for the power of approachingtogether certainly supposes a previous distance, at least equal to thedegree of approach. Consequently, those particles of the air, which arealready considerably distant from each other, tend to separate stillfarther. In fact, if we produce Boyle's vacuum in a large receiver, thevery last portion of air which remains spreads itself uniformly throughthe whole capacity of the vessel, however large, fills it completelythroughout, and presses every where against its sides: We cannot,however, explain this effect, without supposing that the particles makean effort to separate themselves on every side, and we are quiteignorant at what distance, or what degree of rarefaction, this effortceases to act.
Here, therefore, exists a true repulsion between the particles ofelastic fluids; at least, circumstances take place exactly as if such arepulsion actually existed; and we have very good right to conclude,that the particles of caloric mutually repel each other. When we areonce permitted to suppose this repelling force, therationale of theformation of gasses, or aëriform fluids, becomes perfectly simple; tho'we must, at the same time, allow, that it is extremely difficult to forman accurate conception of this repulsive force acting upon very minute[Pg 24]particles placed at great distances from each other.
It is, perhaps, more natural to suppose, that the particles of calorichave a stronger mutual attraction than those of any other substance, andthat these latter particles are forced asunder in consequence of thissuperior attraction between the particles of the caloric, which forcesthem between the particles of other bodies, that they may be able toreunite with each other. We have somewhat analogous to this idea in thephenomena which occur when a dry sponge is dipt into water: The spongeswells; its particles separate from each other; and all its intervalsare filled up by the water. It is evident, that the sponge, in the actof swelling, has acquired a greater capacity for containing water thanit had when dry. But we cannot certainly maintain, that the introductionof water between the particles of the sponge has endowed them with arepulsive power, which tends to separate them from each other; on thecontrary, the whole phenomena are produced by means of attractivepowers; and these are,first, The gravity of the water, and the powerwhich it exerts on every side, in common with all other fluids;2dly,The force of attraction which takes place between the particles of thewater, causing them to unite together;3dly, The mutual attraction ofthe particles of the sponge with each other;[Pg 25] and,lastly, Thereciprocal attraction which exists between the particles of the spongeand those of the water. It is easy to understand, that the explanationof this fact depends upon properly appreciating the intensity of, andconnection between, these several powers. It is probable, that theseparation of the particles of bodies, occasioned by caloric, depends ina similar manner upon a certain combination of different attractivepowers, which, in conformity with the imperfection of our knowledge, weendeavour to express by saying, that caloric communicates a power ofrepulsion to the particles of bodies.
[2] Whenever the degree of heat occurs in this work, it isstated by the author according to Reaumur's scale. The degrees withinbrackets are the correspondent degrees of Fahrenheit's scale, added bythe translator. E.
[3] Collections of the French Academy of Sciences for thatyear, p. 420.
[4] Chemical Nomenclature.
[5] As I shall afterwards give a definition, and explain theproperties of the liquor calledether, I shall only premise here, thatit is a very volatile inflammable liquor, having a considerably smallerspecific gravity than water, or even spirit of wine.—A.
[6] It would have been more satisfactory if the Author hadspecified the degrees of the thermometer at which these heights of themercury in the barometer are produced.
[7] Vide Memoirs of the French Academy, anno 1780, p.335.—A.
These views which I have taken of the formation of elastic aëriformfluids or gasses, throw great light upon the original formation of theatmospheres of the planets, and particularly that of our earth. Wereadily conceive, that it must necessarily consist of a mixture of thefollowing substances:First, Of all bodies that are susceptible ofevaporation, or, more strictly speaking, which are capable of retainingthe state of aëriform elasticity in the temperature of our atmosphere,and under a pressure equal to that of a column of twenty-eight inches ofquicksilver in the barometer; and,secondly, Of all substances,whether liquid or solid, which are capable of being dissolved by thismixture of different gasses.
The better to determine our ideas relating to this subject, which hasnot hitherto been sufficiently considered, let us, for a moment,conceive what change would take place in the various[Pg 27] substances whichcompose our earth, if its temperature were suddenly altered. If, forinstance, we were suddenly transported into the region of the planetMercury, where probably the common temperature is much superior to thatof boiling water, the water of the earth, and all the other fluids whichare susceptible of the gasseous state, at a temperature near to that ofboiling water, even quicksilver itself, would become rarified; and allthese substances would be changed into permanent aëriform fluids orgasses, which would become part of the new atmosphere. These new speciesof airs or gasses would mix with those already existing, and certainreciprocal decompositions and new combinations would take place, untilsuch time as all the elective attractions or affinities subsistingamongst all these new and old gasseous substances had operated fully;after which, the elementary principles composing these gasses, beingsaturated, would remain at rest. We must attend to this, however, that,even in the above hypothetical situation, certain bounds would occur tothe evaporation of these substances, produced by that very evaporationitself; for as, in proportion to the increase of elastic fluids, thepressure of the atmosphere would be augmented, as every degree ofpressure tends, in some measure, to prevent evaporation, and as even themost evaporable[Pg 28] fluids can resist the operation of a very hightemperature without evaporating, if prevented by a proportionallystronger compression, water and all other liquids being able to sustaina red heat in Papin's digester; we must admit, that the new atmospherewould at last arrive at such a degree of weight, that the water whichhad not hitherto evaporated would cease to boil, and, of consequence,would remain liquid; so that, even upon this supposition, as in allothers of the same nature, the increasing gravity of the atmospherewould find certain limits which it could not exceed. We might evenextend these reflections greatly farther, and examine what change mightbe produced in such situations upon stones, salts, and the greater partof the fusible substances which compose the mass of our earth. Thesewould be softened, fused, and changed into fluids, &c.: But thesespeculations carry me from my object, to which I hasten to return.
By a contrary supposition to the one we have been forming, if the earthwere suddenly transported into a very cold region, the water which atpresent composes our seas, rivers, and springs, and probably the greaternumber of the fluids we are acquainted with, would be converted intosolid mountains and hard rocks, at first diaphanous[Pg 29] and homogeneous,like rock crystal, but which, in time, becoming mixed with foreign andheterogeneous substances, would become opake stones of various colours.In this case, the air, or at least some part of the aëriform fluidswhich now compose the mass of our atmosphere, would doubtless lose itselasticity for want of a sufficient temperature to retain them in thatstate: They would return to the liquid state of existence, and newliquids would be formed, of whose properties we cannot, at present, formthe most distant idea.
These two opposite suppositions give a distinct proof of the followingcorollaries:First, Thatsolidity,liquidity, andaëriformelasticity, are only three different states of existence of the samematter, or three particular modifications which almost all substancesare susceptible of assuming successively, and which solely depend uponthe degree of temperature to which they are exposed; or, in other words,upon the quantity of caloric with which they are penetrated[8].2dly,That it is extremely probable that air is a fluid naturally existing ina state of vapour; or, as we may better express it, that our atmosphereis a compound of all the fluids[Pg 30] which are susceptible of the vaporousor permanently elastic state, in the usual temperature, and under thecommon pressure.3dly, That it is not impossible we may discover, inour atmosphere, certain substances naturally very compact, even metalsthemselves; as a metallic substance, for instance, only a little morevolatile than mercury, might exist in that situation.
Amongst the fluids with which we are acquainted, some, as water andalkohol, are susceptible of mixing with each other in all proportions;whereas others, on the contrary, as quicksilver, water, and oil, canonly form a momentary union; and, after being mixed together, separateand arrange themselves according to their specific gravities. The samething ought to, or at least may, take place in the atmosphere. It ispossible, and even extremely probable, that, both at the first creation,and every day, gasses are formed, which are difficultly miscible withatmospheric air, and are continually separating from it. If these gassesbe specifically lighter than the general atmospheric mass, they must, ofcourse, gather in the higher regions, and form strata that float uponthe common air. The phenomena which accompany igneous meteors induce meto believe, that there exists in the upper parts[Pg 31] of our atmosphere astratum of inflammable fluid in contact with those strata of air whichproduce the phenomena of the aurora borealis and other fiery meteors.—Imean hereafter to pursue this subject in a separate treatise.
[8] The degree of pressure which they undergo must be takeninto account. E.
From what has been premised, it follows, that our atmosphere is composedof a mixture of every substance capable of retaining the gasseous oraëriform state in the common temperature, and under the usual pressurewhich it experiences. These fluids constitute a mass, in some measurehomogeneous, extending from the surface of the earth to the greatestheight hitherto attained, of which the density continually decreases inthe inverse ratio of the superincumbent weight. But, as I have beforeobserved, it is possible that this first stratum is surmounted byseveral others consisting of very different fluids.
Our business, in this place, is to endeavour to determine, byexperiments, the nature of the elastic fluids which compose the inferiorstratum of air which we inhabit. Modern chemistry has made greatadvances in this research; and it will appear by the following detailsthat the analysis of atmospherical air has been more[Pg 33] rigorouslydetermined than that of any other substance of the class. Chemistryaffords two general methods of determining the constituent principles ofbodies, the method of analysis, and that of synthesis. When, forinstance, by combining water with alkohol, we form the species of liquorcalled, in commercial language, brandy or spirit of wine, we certainlyhave a right to conclude, that brandy, or spirit of wine, is composed ofalkohol combined with water. We can produce the same result by theanalytical method; and in general it ought to be considered as aprinciple in chemical science, never to rest satisfied without boththese species of proofs.
We have this advantage in the analysis of atmospherical air, being ableboth to decompound it, and to form it a new in the most satisfactorymanner. I shall, however, at present confine myself to recount suchexperiments as are most conclusive upon this head; and I may considermost of these as my own, having either first invented them, or havingrepeated those of others, with the intention of analysing atmosphericalair, in perfectly new points of view.
I took a matrass (A, fig. 14. plate II.) of about 36 cubical inchescapacity, having a long neck B C D E, of six or seven lines internaldiameter, and having bent the neck as in Plate IV. Fig. 2. so as toallow of its being placed in[Pg 34] the furnace M M N N, in such a manner thatthe extremity of its neck E might be inserted under a bell-glass F G,placed in a trough of quicksilver R R S S; I introduced four ounces ofpure mercury into the matrass, and, by means of a syphon, exhausted theair in the receiver F G, so as to raise the quicksilver to L L, and Icarefully marked the height at which it stood by pasting on a slip ofpaper. Having accurately noted the height of the thermometer andbarometer, I lighted a fire in the furnace M M N N, which I kept upalmost continually during twelve days, so as to keep the quicksilveralways almost at its boiling point. Nothing remarkable took place duringthe first day: The Mercury, though not boiling, was continuallyevaporating, and covered the interior surface of the vessels with smalldrops, at first very minute, which gradually augmenting to a sufficientsize, fell back into the mass at the bottom of the vessel. On the secondday, small red particles began to appear on the surface of the mercury,which, during the four or five following days, gradually increased insize and number; after which they ceased to increase in either respect.At the end of twelve days, seeing that the calcination of the mercurydid not at all increase, I extinguished the fire, and allowed thevessels to cool. The bulk of air in the body and neck of the matrass,and in the bell-glass, reduced to[Pg 35] a medium of 28 inches of thebarometer and 10° (54.5°) of the thermometer, at the commencement of theexperiment was about 50 cubical inches. At the end of the experiment theremaining air, reduced to the same medium pressure and temperature, wasonly between 42 and 43 cubical inches; consequently it had lost about1/6 of its bulk. Afterwards, having collected all the red particles,formed during the experiment, from the running mercury in which theyfloated, I found these to amount to 45 grains.
I was obliged to repeat this experiment several times, as it isdifficult in one experiment both to preserve the whole air upon which weoperate, and to collect the whole of the red particles, or calx ofmercury, which is formed during the calcination. It will often happen inthe sequel, that I shall, in this manner, give in one detail the resultsof two or three experiments of the same nature.
The air which remained after the calcination of the mercury in thisexperiment, and which was reduced to 5/6 of its former bulk, was nolonger fit either for respiration or for combustion; animals beingintroduced into it were suffocated in a few seconds, and when a taperwas plunged into it, it was extinguished as if it had been immersed intowater.[Pg 36]
In the next place, I took the 45 grains of red matter formed during thisexperiment, which I put into a small glass retort, having a properapparatus for receiving such liquid, or gasseous product, as might beextracted: Having applied a fire to the retort in a furnace, I observedthat, in proportion as the red matter became heated, the intensity ofits colour augmented. When the retort was almost red hot, the red matterbegan gradually to decrease in bulk, and in a few minutes after itdisappeared altogether; at the same time 41-1/2 grains of runningmercury were collected in the recipient, and 7 or 8 cubical inches ofelastic fluid, greatly more capable of supporting both respiration andcombustion than atmospherical air, were collected in the bell-glass.
A part of this air being put into a glass tube of about an inchdiameter, showed the following properties: A taper burned in it with adazzling splendour, and charcoal, instead of consuming quietly as itdoes in common air, burnt with a flame, attended with a decrepitatingnoise, like phosphorus, and threw out such a brilliant light that theeyes could hardly endure it. This species of air was discovered almostat the same time by Mr Priestley, Mr Scheele, and myself. Mr Priestleygave it the name ofdephlogisticated air, Mr Scheele called itempyreal air. At first I named ithighly respirable air, to[Pg 37] whichhas since been substituted the term ofvital air. We shall presentlysee what we ought to think of these denominations.
In reflecting upon the circumstances of this experiment, we readilyperceive, that the mercury, during its calcination, absorbs thesalubrious and respirable part of the air, or, to speak more strictly,the base of this respirable part; that the remaining air is a species ofmephitis, incapable of supporting combustion or respiration; andconsequently that atmospheric air is composed of two elastic fluids ofdifferent and opposite qualities. As a proof of this important truth, ifwe recombine these two elastic fluids, which we have separately obtainedin the above experiment, viz. the 42 cubical inches of mephitis, withthe 8 cubical inches of respirable air, we reproduce an air preciselysimilar to that of the atmosphere, and possessing nearly the same powerof supporting combustion and respiration, and of contributing to thecalcination of metals.
Although this experiment furnishes us with a very simple means ofobtaining the two principal elastic fluids which compose our atmosphere,separate from each other, yet it does not give us an exact idea of theproportion in which these two enter into its composition: For theattraction of mercury to the respirable part of the air, or rather toits base, is not sufficiently strong to overcome all the circumstanceswhich[Pg 38] oppose this union. These obstacles are the mutual adhesion of thetwo constituent parts of the atmosphere for each other, and the electiveattraction which unites the base of vital air with caloric; inconsequence of these, when the calcination ends, or is at least carriedas far as is possible, in a determinate quantity of atmospheric air,there still remains a portion of respirable air united to the mephitis,which the mercury cannot separate. I shall afterwards show, that, atleast in our climate, the atmospheric air is composed of respirable andmephitic airs, in the proportion of 27 and 73; and I shall then discussthe causes of the uncertainty which still exists with respect to theexactness of that proportion.
Since, during the calcination of mercury, air is decomposed, and thebase of its respirable part is fixed and combined with the mercury, itfollows, from the principles already established, that caloric and lightmust be disengaged during the process: But the two following causesprevent us from being sensible of this taking place: As the calcinationlasts during several days, the disengagement of caloric and light,spread out in a considerable space of time, becomes extremely small foreach particular moment of that time, so as not to be perceptible; and,in the next place, the operation being carried on by means of fire in afurnace, the heat[Pg 39] produced by the calcination itself becomes confoundedwith that proceeding from the furnace. I might add the respirable partof the air, or rather its base, in entering into combination with themercury, does not part with all the caloric which it contained, butstill retains a part of it after forming the new compound; but thediscussion of this point, and its proofs from experiment, do not belongto this part of our subject.
It is, however, easy to render this disengagement of caloric and lightevident to the senses, by causing the decomposition of air to take placein a more rapid manner. And for this purpose, iron is excellentlyadapted, as it possesses a much stronger affinity for the base ofrespirable air than mercury. The elegant experiment of Mr Ingenhouz,upon the combustion of iron, is well known. Take a piece of fine ironwire, twisted into a spiral, (BC, Plate IV. Fig. 17.) fix one of itsextremities B into the cork A, adapted to the neck of the bottle DEFG,and fix to the other extremity of the wire C, a small morsel of tinder.Matters being thus prepared, fill the bottle DEFG with air deprived ofits mephitic part; then light the tinder, and introduce it quickly withthe wire upon which it is fixed, into the bottle which you stop up withthe cork A, as is shown in the figure (17 Plate IV.) The instant the[Pg 40]tinder comes into contact with the vital air it begins to burn withgreat intensity; and, communicating the inflammation to the iron-wire,it too takes fire, and burns rapidly, throwing out brilliant sparks,which fall to the bottom of the vessel in rounded globules, which becomeblack in cooling, but retain a degree of metallic splendour. The ironthus burnt is more brittle even than glass, and is easily reduced intopowder, and is still attractable by the magnet, though not so powerfullyas it was before combustion. As Mr Ingenhouz has neither examined thechange produced on iron, nor upon the air by this operation, I haverepeated the experiment under different circumstances, in an apparatusadapted to answer my particular views, as follows.
Having filled a bell-glass (A, Plate IV. Fig. 3.) of about six pintsmeasure, with pure air, or the highly respirable part of air, Itransported this jar by means of a very flat vessel, into a quicksilverbath in the bason BC, and I took care to render the surface of themercury perfectly dry both within and without the jar with blottingpaper. I then provided a small capsule of china-ware D, very flat andopen, in which I placed some small pieces of iron, turned spirally, andarranged in such a way as seemed most favourable for the combustionbeing communicated to every part. To the end of one of these pieces ofiron was[Pg 41] fixed a small morsel of tinder, to which was added about thesixteenth part of a grain of phosphorus, and, by raising the bell-glassa little, the china capsule, with its contents, were introduced into thepure air. I know that, by this means, some common air must mix with thepure air in the glass; but this, when it is done dexterously, is so verytrifling, as not to injure the success of the experiment. This beingdone, a part of the air is sucked out from the bell-glass, by means of asyphon GHI, so as to raise the mercury within the glass to EF; and, toprevent the mercury from getting into the syphon, a small piece of paperis twisted round its extremity. In sucking out the air, if the motion ofthe lungs only be used, we cannot make the mercury rise above an inch oran inch and a half; but, by properly using the muscles of the mouth, wecan, without difficulty, cause it to rise six or seven inches.
I next took an iron wire, (MN, Plate IV. Fig. 16.) properly bent for thepurpose, and making it red hot in the fire, passed it through themercury into the receiver, and brought it in contact with the smallpiece of phosphorus attached to the tinder. The phosphorus instantlytakes fire, which communicates to the tinder, and from that to the iron.When the pieces have been properly arranged, the whole iron burns, evento the last particle,[Pg 42] throwing out a white brilliant light similar tothat of Chinese fireworks. The great heat produced by this combustionmelts the iron into round globules of different sizes, most of whichfall into the China cup; but some are thrown out of it, and swim uponthe surface of the mercury. At the beginning of the combustion, there isa slight augmentation in the volume of the air in the bell-glass, fromthe dilatation caused by the heat; but, presently afterwards, a rapiddiminution of the air takes place, and the mercury rises in the glass;insomuch that, when the quantity of iron is sufficient, and the airoperated upon is very pure, almost the whole air employed is absorbed.
It is proper to remark in this place, that, unless in making experimentsfor the purpose of discovery, it is better to be contented with burninga moderate quantity of iron; for, when this experiment is pushed toofar, so as to absorb much of the air, the cup D, which floats upon thequicksilver, approaches too near the bottom of the bell-glass; and thegreat heat produced, which is followed by a very sudden cooling,occasioned by the contact of the cold mercury, is apt to break theglass. In which case, the sudden fall of the column of mercury, whichhappens the moment the least flaw is produced in the glass, causes sucha wave, as throws a great part of the quicksilver from the bason. Toavoid[Pg 43] this inconvenience, and to ensure success to the experiment, onegross and a half of iron is sufficient to burn in a bell-glass, whichholds about eight pints of air. The glass ought likewise to be strong,that it may be able to bear the weight of the column of mercury which ithas to support.
By this experiment, it is not possible to determine, at one time, boththe additional weight acquired by the iron, and the changes which havetaken place in the air. If it is wished to ascertain what additionalweight has been gained by the iron, and the proportion between that andthe air absorbed, we must carefully mark upon the bell-glass, with adiamond, the height of the mercury, both before and after theexperiment[9]. After this, the syphon (GH, Pl. IV. fig. 3.) guarded, asbefore, with a bit of paper, to prevent its filling with mercury, is tobe introduced under the bell-glass, having the thumb placed upon theextremity, G, of the syphon, to regulate the passage of the air; and bythis means the air is gradually admitted, so as to let the mercury fallto its level. This being done, the bell-glass is to be carefullyremoved, the[Pg 44] globules of melted iron contained in the cup, and thosewhich have been scattered about, and swim upon the mercury, are to beaccurately collected, and the whole is to be weighed. The iron will befound in that state calledmartial ethiops by the old chemists,possessing a degree of metallic brilliancy, very friable, and readilyreducible into powder, under the hammer, or with a pestle and mortar. Ifthe experiment has succeeded well, from 100 grains of iron will beobtained 135 or 136 grains of ethiops, which is an augmentation of 35per cent.
If all the attention has been paid to this experiment which it deserves,the air will be found diminished in weight exactly equal to what theiron has gained. Having therefore burnt 100 grains of iron, which hasacquired an additional weight of 35 grains, the diminution of air willbe found exactly 70 cubical inches; and it will be found, in the sequel,that the weight of vital air is pretty nearly half a grain for eachcubical inch; so that, in effect, the augmentation of weight in the oneexactly coincides with the loss of it in the other.
I shall observe here, once for all, that, in every experiment of thiskind, the pressure and temperature of the air, both before and after theexperiment, must be reduced, by calculation, to a common standard of 10°(54.5°) of the thermometer, and 28 inches of the barometer.[Pg 45] Towards theend of this work, the manner of performing this very necessary reductionwill be found accurately detailed.
If it be required to examine the nature of the air which remains afterthis experiment, we must operate in a somewhat different manner. Afterthe combustion is finished, and the vessels have cooled, we first takeout the cup, and the burnt iron, by introducing the hand through thequicksilver, under the bell-glass; we next introduce some solution ofpotash, or caustic alkali, or of the sulphuret of potash, or such othersubstance as is judged proper for examining their action upon theresiduum of air. I shall, in the sequel, give an account of thesemethods of analysing air, when I have explained the nature of thesedifferent substances, which are only here in a manner accidentallymentioned. After this examination, so much water must be let into theglass as will displace the quicksilver, and then, by means of a shallowdish placed below the bell-glass, it is to be removed into the commonwater pneumato-chemical apparatus, where the air remaining may beexamined at large, and with great facility.
When very soft and very pure iron has been employed in this experiment,and, if the combustion has been performed in the purest respirable orvital air, free from all admixture of the noxious or mephitic part, theair which remains[Pg 46] after the combustion will be found as pure as it wasbefore; but it is difficult to find iron entirely free from a smallportion of charry matter, which is chiefly abundant in steel. It islikewise exceedingly difficult to procure the pure air perfectly freefrom some admixture of mephitis, with which it is almost alwayscontaminated; but this species of noxious air does not, in the smallestdegree, disturb the result of the experiment, as it is always found atthe end exactly in the same proportion as at the beginning.
I mentioned before, that we have two ways of determining the constituentparts of atmospheric air, the method of analysis, and that by synthesis.The calcination of mercury has furnished us with an example of each ofthese methods, since, after having robbed the respirable part of itsbase, by means of the mercury, we have restored it, so as to recomposean air precisely similar to that of the atmosphere. But we can equallyaccomplish this synthetic composition of atmospheric air, by borrowingthe materials of which it is composed from different kingdoms of nature.We shall see hereafter that, when animal substances are dissolved in thenitric acid, a great quantity of gas is disengaged, which extinguisheslight, and is unfit for animal respiration, being exactly similar to thenoxious or mephitic part of atmospheric air. And, if we take 73 parts,by weight, of this elastic[Pg 47] fluid, and mix it with 27 parts of highlyrespirable air, procured from calcined mercury, we will form an elasticfluid precisely similar to atmospheric air in all its properties.
There are many other methods of separating the respirable from thenoxious part of the atmospheric air, which cannot be taken notice of inthis part, without anticipating information, which properly belongs tothe subsequent chapters. The experiments already adduced may suffice foran elementary treatise; and, in matters of this nature, the choice ofour evidences is of far greater consequence than their number.
I shall close this article, by pointing out the property whichatmospheric air, and all the known gasses, possess of dissolving water,which is of great consequence to be attended to in all experiments ofthis nature. Mr Saussure found, by experiment, that a cubical foot ofatmospheric air is capable of holding 12 grains of water in solution:Other gasses, as the carbonic acid, appear capable of dissolving agreater quantity; but experiments are still wanting by which todetermine their several proportions. This water, held in solution bygasses, gives rise to particular phenomena in many experiments, whichrequire great attention, and which has frequently proved the source ofgreat errors to chemists in determining the results of theirexperiments.
[9] It will likewise be necessary to take care that the aircontained in the glass, both before and after the experiment, be reducedto a common temperature and pressure, otherwise the results of thefollowing calculations will be fallacious.—E.
Hitherto I have been obliged to make use of circumlocution, to expressthe nature of the several substances which constitute our atmosphere,having provisionally used the terms ofrespirable andnoxious, ornon-respirable parts of the air. But the investigations I mean toundertake require a more direct mode of expression; and, having nowendeavoured to give simple and distinct ideas of the differentsubstances which enter into the composition of the atmosphere, I shallhenceforth express these ideas by words equally simple.
The temperature of our earth being very near to that at which waterbecomes solid, and reciprocally changes from solid to fluid, and as thisphenomenon takes place frequently under our observation, it has verynaturally followed, that, in the languages of at least every climatesubjected to any degree of winter, a term has been used for signifyingwater in the state of solidity, when deprived of its caloric. The same,however, has not been found necessary[Pg 49] with respect to water reduced tothe state of vapour by an additional dose of caloric; since thosepersons who do not make a particular study of objects of this kind, arestill ignorant that water, when in a temperature only a little above theboiling heat, is changed into an elastic aëriform fluid, susceptible,like all other gasses, of being received and contained in vessels, andpreserving its gasseous form so long as it remains at the temperature of80° (212°), and under a pressure not exceeding 28 inches of themercurial barometer. As this phenomenon has not been generally observed,no language has used a particular term for expressing water in thisstate[10]; and the same thing occurs with all fluids, and allsubstances, which do not evaporate in the common temperature, and underthe usual pressure of our atmosphere.
For similar reasons, names have not been given to the liquid or concretestates of most of the aëriform fluids: These were not known to arisefrom the combination of caloric with certain bases; and, as they had notbeen seen either in the liquid or solid states, their existence, underthese forms, was even unknown to natural philosophers.[Pg 50]
We have not pretended to make any alteration upon such terms as aresanctified by ancient custom; and, therefore, continue to use the wordswater andice in their common acceptation: We likewise retain thewordair, to express that collection of elastic fluids which composesour atmosphere; but we have not thought it necessary to preserve thesame respect for modern terms, adopted by latter philosophers, havingconsidered ourselves as at liberty to reject such as appeared liable tooccasion erroneous ideas of the substances they are meant to express,and either to substitute new terms, or to employ the old ones, aftermodifying them in such a manner as to convey more determinate ideas. Newwords have been drawn, chiefly from the Greek language, in such a manneras to make their etymology convey some idea of what was meant to berepresented; and these we have always endeavoured to make short, and ofsuch a nature as to be changeable into adjectives and verbs.
Following these principles, we have, after Mr Macquer's example,retained the termgas, employed by Vanhelmont, having arranged thenumerous class of elastic aëriform fluids under that name, exceptingonly atmospheric air.Gas, therefore, in our nomenclature, becomes ageneric term, expressing the fullest degree of saturation in any bodywith caloric; being, in[Pg 51] fact, a term expressive of a mode of existence.To distinguish each species of gas, we employ a second term from thename of the base, which, saturated with caloric, forms each particulargas. Thus, we name water combined to saturation with caloric, so as toform an elastic fluid,aqueous gas; ether, combined in the samemanner,etherial gas; the combination of alkohol with caloric, becomesalkoholic gas; and, following the same principles, we havemuriaticacid gas,ammoniacal gas, and so on of every substance susceptible ofbeing combined with caloric, in such a manner as to assume the gasseousor elastic aëriform state.
We have already seen, that the atmospheric air is composed of twogasses, or aëriform fluids, one of which is capable, by respiration, ofcontributing to animal life, and in which metals are calcinable, andcombustible bodies may burn; the other, on the contrary, is endowed withdirectly opposite qualities; it cannot be breathed by animals, neitherwill it admit of the combustion of inflammable bodies, nor of thecalcination of metals. We have given to the base of the former, orrespirable portion of the air, the name ofoxygen, from οξυςacidum, and γεινομας,gignor; because, in reality, one ofthe most general properties of this base is to form acids, by combiningwith many different substances. The union of this base with caloric[Pg 52] wetermoxygen gas, which is the same with what was formerly calledpure, orvital air. The weight of this gas, at the temperature of10° (54.50), and under a pressure equal to 28 inches of the barometer,is half a grain for each cubical inch, or one ounce and a half to eachcubical foot.
The chemical properties of the noxious portion of atmospheric air beinghitherto but little known, we have been satisfied to derive the name ofits base from its known quality of killing such animals as are forced tobreathe it, giving it the name ofazote, from the Greek privitiveparticle α and ξαη, vita; hence the name of thenoxious part of atmospheric air isazotic gas; the weight of which, inthe same temperature, and under the same pressure, is 1oz. 2gros.and 48grs. to the cubical foot, or 0.4444 of a grain to the cubicalinch. We cannot deny that this name appears somewhat extraordinary; butthis must be the case with all new terms, which cannot be expected tobecome familiar until they have been some time in use. We longendeavoured to find a more proper designation without success; it was atfirst proposed to call italkaligen gas, as, from the experiments ofMr Berthollet, it appears to enter into the composition of ammoniac, orvolatile alkali; but then, we have as yet no proof of its making one ofthe constituent elements of[Pg 53] the other alkalies; beside, it is proved tocompose a part of the nitric acid, which gives as good reason to havecalled itnitrigen. For these reasons, finding it necessary to rejectany name upon systematic principles, we have considered that we run norisk of mistake in adopting the terms ofazote, andazotic gas,which only express a matter of fact, or that property which itpossesses, of depriving such animals as breathe it of their lives.
I should anticipate subjects more properly reserved for the subsequentchapters, were I in this place to enter upon the nomenclature of theseveral species of gasses: It is sufficient, in this part of the work,to establish the principles upon which their denominations are founded.The principal merit of the nomenclature we have adopted is, that, whenonce the simple elementary substance is distinguished by an appropriateterm, the names of all its compounds derive readily, and necessarily,from this first denomination.
[10] In English, the wordsteam is exclusively appropriatedto water in the state of vapour. E.
In performing experiments, it is a necessary principle, which oughtnever to be deviated from, that they be simplified as much as possible,and that every circumstance capable of rendering their resultscomplicated be carefully removed. Wherefore, in the experiments whichform the object of this chapter, we have never employed atmospheric air,which is not a simple substance. It is true, that the azotic gas, whichforms a part of its mixture, appears to be merely passive duringcombustion and calcination; but, besides that it retards theseoperations very considerably, we are not certain but it may even altertheir results in some circumstances; for which reason, I have thought itnecessary to remove even this possible cause of doubt, by only makinguse of pure oxygen gas in the following experiments, which show theeffects produced by combustion in that gas; and I shall advert to suchdifferences as take place in the results of these, when the oxygen gas,or pure[Pg 55] vital air, is mixed, in different proportions, with azotic gas.
Having filled a bell-glass (A. Pl. iv. fig. 3), of between five and sixpints measure, with oxygen gas, I removed it from the water trough,where it was filled, into the quicksilver bath, by means of a shallowglass dish slipped underneath, and having dried the mercury, Iintroduced 61-1/4 grains of Kunkel's phosphorus in two little Chinacups, like that represented at D, fig. 3. under the glass A; and that Imight set fire to each of the portions of phosphorus separately, and toprevent the one from catching fire from the other, one of the dishes wascovered with a piece of flat glass. I next raised the quicksilver in thebell-glass up to E F, by sucking out a sufficient portion of the gas bymeans of the syphon G H I. After this, by means of the crooked iron wire(fig. 16.), made red hot, I set fire to the two portions of phosphorussuccessively, first burning that portion which was not covered with thepiece of glass. The combustion was extremely rapid, attended with a verybrilliant flame, and considerable disengagement of light and heat. Inconsequence of the great heat induced, the gas was at first muchdilated, but soon after the mercury returned to its level, and aconsiderable absorption of gas took place; at the same time, the[Pg 56] wholeinside of the glass became covered with white light flakes of concretephosphoric acid.
At the beginning of the experiment, the quantity of oxygen gas, reduced,as above directed, to a common standard, amounted to 162 cubical inches;and, after the combustion was finished, only 23-1/4 cubical inches,likewise reduced to the standard, remained; so that the quantity ofoxygen gas absorbed during the combustion was 138-3/4 cubical inches,equal to 69.375 grains.
A part of the phosphorus remained unconsumed in the bottom of the cups,which being washed on purpose to separate the acid, weighed about 16-1/4grains; so that about 45 grains of phosphorus had been burned: But, asit is hardly possible to avoid an error of one or two grains, I leavethe quantity so far qualified. Hence, as nearly 45 grains of phosphorushad, in this experiment, united with 69.375 grains of oxygen, and as nogravitating matter could have escaped through the glass, we have a rightto conclude, that the weight of the substance resulting from thecombustion in form of white flakes, must equal that of the phosphorusand oxygen employed, which amounts to 114.375 grains. And we shallpresently find, that these flakes consisted entirely of a solid orconcrete acid. When we reduce these weights to hundredth parts, it willbe found, that 100 parts of[Pg 57] phosphorus require 154 parts of oxygen forsaturation, and that this combination will produce 254 parts of concretephosphoric acid, in form of white fleecy flakes.
This experiment proves, in the most convincing manner, that, at acertain degree of temperature, oxygen possesses a stronger electiveattraction, or affinity, for phosphorus than for caloric; that, inconsequence of this, the phosphorus attracts the base of oxygen gas fromthe caloric, which, being set free, spreads itself over the surroundingbodies. But, though this experiment be so far perfectly conclusive, itis not sufficiently rigorous, as, in the apparatus described, it isimpossible to ascertain the weight of the flakes of concrete acid whichare formed; we can therefore only determine this by calculating theweights of oxygen and phosphorus employed; but as, in physics, and inchemistry, it is not allowable to suppose what is capable of beingascertained by direct experiment, I thought it necessary to rep at thisexperiment, as follows, upon a larger scale, and by means of a differentapparatus.
I took a large glass baloon (A. Pl. iv. fig. 4.) with an opening threeinches diameter, to which was fitted a crystal stopper ground withemery, and pierced with two holes for the tubes yyy, xxx. Beforeshutting the baloon with its stopper, I introduced the support BC,surmounted[Pg 58] by the china cup D, containing 150grs. of phosphorus; thestopper was then fitted to the opening of the baloon, luted with fatlute, and covered with slips of linen spread with quick-lime and whiteof eggs: When the lute was perfectly dry, the weight of the wholeapparatus was determined to within a grain, or a grain and a half. Inext exhausted the baloon, by means of an air pump applied to the tubexxx, and then introduced oxygen gas by means of the tube yyy, having astop cock adapted to it. This kind of experiment is most readily andmost exactly performed by means of the hydro-pneumatic machine describedby Mr Meusnier and me in the Memoirs of the Academy for 1782, pag. 466.and explained in the latter part of this work, with several importantadditions and corrections since made to it by Mr Meusnier. With thisinstrument we can readily ascertain, in the most exact manner, both thequantity of oxygen gas introduced into the baloon, and the quantityconsumed during the course of the experiment.
When all things were properly disposed, I set fire to the phosphoruswith a burning glass. The combustion was extremely rapid, accompaniedwith a bright flame, and much heat; as the operation went on, largequantities of white flakes attached themselves to the inner surface ofthe baloon, so that at last it was rendered[Pg 59] quite opake. The quantityof these flakes at last became so abundant, that, although fresh oxygengas was continually supplied, which ought to have supported thecombustion, yet the phosphorus was soon extinguished. Having allowed theapparatus to cool completely, I first ascertained the quantity of oxygengas employed, and weighed the baloon accurately, before it was opened. Inext washed, dried, and weighed the small quantity of phosphorusremaining in the cup, on purpose to determine the whole quantity ofphosphorus consumed in the experiment; this residuum of the phosphoruswas of a yellow ochrey colour. It is evident, that by these severalprecautions, I could easily determine, 1st, the weight of the phosphorusconsumed; 2d, the weight of the flakes produced by the combustion; and,3d, the weight of the oxygen which had combined with the phosphorus.This experiment gave very nearly the same results with the former, as itproved that the phosphorus, during its combustion, had absorbed a littlemore than one and a half its weight of oxygen; and I learned with morecertainty, that the weight of the new substance, produced in theexperiment, exactly equalled the sum of the weights of the phosphorusconsumed, and oxygen absorbed, which indeed was easily determinableapriori. If the oxygen gas employed be pure, the residuum aftercombustion[Pg 60] is as pure as the gas employed; this proves that nothingescapes from the phosphorus, capable of altering the purity of theoxygen gas, and that the only action of the phosphorus is to separatethe oxygen from the caloric, with which it was before united.
I mentioned above, that when any combustible body is burnt in a hollowsphere of ice, or in an apparatus properly constructed upon thatprinciple, the quantity of ice melted during the combustion is an exactmeasure of the quantity of caloric disengaged. Upon this head, thememoir given by M. de la Place and me, Aº. 1780, p. 355, may beconsulted. Having submitted the combustion of phosphorus to this trial,we found that one pound of phosphorus melted a little more than 100pounds of ice during its combustion.
The combustion of phosphorus succeeds equally well in atmospheric air asin oxygen gas, with this difference, that the combustion is vastlyslower, being retarded by the large proportion of azotic gas mixed withthe oxygen gas, and that only about one-fifth part of the air employedis absorbed, because as the oxygen gas only is absorbed, the proportionof the azotic gas becomes so great toward the close of the experiment,as to put an end to the combustion.[Pg 61]
I have already shown, that phosphorus is changed by combustion into anextremely light, white, flakey matter; and its properties are entirelyaltered by this transformation: From being insoluble in water, itbecomes not only soluble, but so greedy of moisture, as to attract thehumidity of the air with astonishing rapidity; by this means it isconverted into a liquid, considerably more dense, and of more specificgravity than water. In the state of phosphorus before combustion, it hadscarcely any sensible taste, by its union with oxygen it acquires anextremely sharp and sour taste: in a word, from one of the class ofcombustible bodies, it is changed into an incombustible substance, andbecomes one of those bodies called acids.
This property of a combustible substance to be converted into an acid,by the addition of oxygen, we shall presently find belongs to a greatnumber of bodies: Wherefore, strict logic requires that we should adopta common term for indicating all these operations which produceanalogous results; this is the true way to simplify the study ofscience, as it would be quite impossible to bear all its specificaldetails in the memory, if they were not classically arranged. For thisreason, we shall distinguish this conversion of phosphorus into an acid,by its union with oxygen, and in general every combination of oxygenwith a combustible substance,[Pg 62] by the term ofoxygenation: from whichI shall adopt the verb tooxygenate, and of consequence shall say,that inoxygenating phosphorus we convert it into an acid.
Sulphur is likewise a combustible body, or, in other words, it is a bodywhich possesses the power of decomposing oxygen gas, by attracting theoxygen from the caloric with which it was combined. This can very easilybe proved, by means of experiments quite similar to those we have givenwith phosphorus; but it is necessary to premise, that in theseoperations with sulphur, the same accuracy of result is not to beexpected as with phosphorus; because the acid which is formed by thecombustion of sulphur is difficultly condensible, and because sulphurburns with more difficulty, and is soluble in the different gasses. ButI can safely assert, from my own experiments, that sulphur in burningabsorbs oxygen gas; that the resulting acid is considerably heavier thanthe sulphur burnt; that its weight is equal to the sum of the weights ofthe sulphur which has been burnt, and of the oxygen absorbed; and,lastly that this acid is weighty, incombustible, and miscible with waterin all proportions: The only uncertainty remaining upon this head, iswith regard to the proportions of sulphur and of oxygen which enter intothe composition of the acid.[Pg 63]
Charcoal, which, from all our present knowledge regarding it, must beconsidered as a simple combustible body, has likewise the property ofdecomposing oxygen gas, by absorbing its base from the caloric: But theacid resulting from this combustion does not condense in the commontemperature; under the pressure of our atmosphere, it remains in thestate of gas, and requires a large proportion of water to combine withor be dissolved in. This acid has, however, all the known properties ofother acids, though in a weaker degree, and combines, like them, withall the bases which are susceptible of forming neutral salts.
The combustion of charcoal in oxygen gas, may be effected like that ofphosphorus in the bell-glass, (A. Pl. IV. fig. 3.) placed over mercury:but, as the heat of red hot iron is not sufficient to set fire to thecharcoal, we must add a small morsel of tinder, with a minute particleof phosphorus, in the same manner as directed in the experiment for thecombustion of iron. A detailed account of this experiment will be foundin the memoirs of the academy for 1781, p. 448. By that experiment itappears, that 28 parts by weight of charcoal require 72 parts of oxygenfor saturation, and that the aëriform acid produced is precisely equalin weight to the sum of the weights of the charcoal and oxygen gasemployed.[Pg 64] This aëriform acid was called fixed or fixable air by thechemists who first discovered it; they did not then know whether it wasair resembling that of the atmosphere, or some other elastic fluid,vitiated and corrupted by combustion; but since it is now ascertained tobe an acid, formed like all others by the oxygenation of its peculiarbase, it is obvious that the name of fixed air is quite ineligible[11].
By burning charcoal in the apparatus mentioned p. 60, Mr de la Place andI found that onelib. of charcoal melted 96libs. 6oz. of ice;that, during the combustion, 2libs. 9oz. 1gros. 10grs. ofoxygen were absorbed, and that 3libs. 9oz. 1gros. 10grs. ofacid gas were formed. This gas weighs 0.695 parts of a grain for eachcubical inch, in the common standard temperature and pressure mentionedabove, so that 34,242 cubical inches of acid gas are produced by thecombustion of one pound of charcoal.
I might multiply these experiments, and show by a numerous succession offacts, that all acids are formed by the combustion of certainsubstances; but I am prevented from doing so in[Pg 65] place, by the planwhich I have laid down, of proceeding only from facts alreadyascertained, to such as are unknown, and of drawing my examples onlyfrom circumstances already explained. In the mean time, however, thethree examples above cited may suffice for giving a clear and accurateconception of the manner in which acids are formed. By these it may beclearly seen, that oxygen is an element common to them all, whichconstitutes their acidity; and that they differ from each other,according to the nature of the oxygenated or acidified substance. Wemust therefore, in every acid, carefully distinguish between theacidifiable, base, which Mr de Morveau calls the radical, and theacidifiing principle or oxygen.
[11] It may be proper to remark, though here omitted by theauthor, that, in conformity with the general principles of the newnomenclature, this acid is by Mr Lavoisier and his coleagues called thecarbonic acid, and when in the aëriform state carbonic acid gas. E.
It becomes extremely easy, from the principles laid down in thepreceding chapter, to establish a systematic nomenclature for the acids:The wordacid, being used as a generic term, each acid falls to bedistinguished in language, as in nature, by the name of its base orradical. Thus, we give the generic name of acids to the products of thecombustion or oxygenation of phosphorus, of sulphur, and of charcoal;and these products are respectively named, thephosphoric acid, thesulphuric acid, and thecarbonic acid.
There is however, a remarkable circumstance in the oxygenation ofcombustible bodies, and of a part of such bodies as are convertible intoacids, that they are susceptible of different degrees of saturation withoxygen, and that the resulting acids, though formed by the union of thesame elements, are possessed of different properties, depending uponthat difference of proportion. Of this, the phosphoric acid, and moreespecially the sulphuric, furnishes us with examples.[Pg 67] When sulphur iscombined with a small proportion of oxygen, it forms, in this first orlower degree of oxygenation, a volatile acid, having a penetratingodour, and possessed of very particular qualities. By a largerproportion of oxygen, it is changed into a fixed, heavy acid, withoutany odour, and which, by combination with other bodies, gives productsquite different from those furnished by the former. In this instance,the principles of our nomenclature seem to fail; and it seems difficultto derive such terms from the name of the acidifiable base, as shalldistinctly express these two degrees of saturation, or oxygenation,without circumlocution. By reflection, however, upon the subject, orperhaps rather from the necessity of the case, we have thought itallowable to express these varieties in the oxygenation of the acids, bysimply varying the termination of their specific names. The volatileacid produced from sulphur was anciently known to Stahl under the nameofsulphurous acid[12]. We have[Pg 68] preserved that term for this acidfrom sulphur under-saturated with oxygen; and distinguish the other, orcompletely saturated or oxygenated acid, by the name ofsulphuricacid. We shall therefore say, in this new chemical language, thatsulphur, in combining with oxygen, is susceptible of two degrees ofsaturation; that the first, or lesser degree, constitutes sulphurousacid, which is volatile and penetrating; whilst the second, or higherdegree of saturation, produces sulphuric acid, which is fixed andinodorous. We shall adopt this difference of termination for all theacids which assume several degrees of saturation. Hence we have aphosphorous and a phosphoric acid, an acetous and an acetic acid; and soon, for others in similar circumstances.
This part of chemical science would have been extremely simple, and thenomenclature of the acids would not have been at all perplexed, as it isnow in the old nomenclature, if the base or radical of each acid hadbeen known when the acid itself was discovered. Thus, for instance,phosphorus being a known substance before the discovery of its acid,this latter was rightly distinguished by a term drawn from the name ofits acidifiable base. But when, on the contrary, an acid happened to bediscovered before its base, or rather, when the acidifiable base fromwhich it was formed remained unknown,[Pg 69] names were adopted for the two,which have not the smallest connection; and thus, not only the memorybecame burthened with useless appellations, but even the minds ofstudents, nay even of experienced chemists, became filled with falseideas, which time and reflection alone is capable of eradicating. We maygive an instance of this confusion with respect to the acid sulphur: Theformer chemists having procured this acid from the vitriol of iron, gaveit the name of the vitriolic acid from the name of the substance whichproduced it; and they were then ignorant that the acid procured fromsulphur by combustion was exactly the same.
The same thing happened with the aëriform acid formerly calledfixedair; it not being known that this acid was the result of combiningcharcoal with oxygen, a variety of denominations have been given to it,not one of which conveys just ideas of its nature or origin. We havefound it extremely easy to correct and modify the ancient language withrespect to these acids proceeding from known bases, having converted thename ofvitriolic acid into that ofsulphuric, and the name offixed air into that ofcarbonic acid; but it is impossible to followthis plan with the acids whose bases are still unknown; with these wehave been obliged to use a contrary plan, and, instead of forming thename of the acid from that of its[Pg 70] base, have been forced to denominatethe unknown base from the name of the known acid, as happens in the caseof the acid which is procured from sea salt.
To disengage this acid from the alkaline base with which it is combined,we have only to pour sulphuric acid upon sea-salt, immediately a briskeffervescence takes place, white vapours arise, of a very penetratingodour, and, by only gently heating the mixture, all the acid is drivenoff. As, in the common temperature and pressure of our atmosphere, thisacid is naturally in the state of gas, we must use particularprecautions for retaining it in proper vessels. For small experiments,the most simple and most commodious apparatus consists of a small retortG, (Pl. V. Fig. 5.), into which the sea-salt is introduced, welldried[13], we then pour on some concentrated sulphuric acid, andimmediately introduce the beak of the retort under little jars orbell-glasses A, (same Plate and Fig.), previously filled withquicksilver. In proportion as the acid gas is disengaged, it passes intothe jar, and gets to the top of the quicksilver, which it displaces.When the disengagement[Pg 71] of the gas slackens, a gentle heat is applied tothe retort, and gradually increased till nothing more passes over. Thisacid gas has a very strong affinity with water, which absorbs anenormous quantity of it, as is proved by introducing a very thin layerof water into the glass which contains the gas; for, in an instant, thewhole acid gas disappears, and combines with the water.
This latter circumstance is taken advantage of in laboratories andmanufactures, on purpose to obtain the acid of sea-salt in a liquidform; and for this purpose the apparatus (Pl. IV. Fig. 1.) is employed.It consists, 1st, of a tubulated retort A, into which the sea-salt, andafter it the sulphuric acid, are introduced through the opening H; 2d,of the baloon or recipientc,b, intended for containing the smallquantity of liquid which passes over during the process; and, 3d, of aset of bottles, with two mouths, L, L, L, L, half filled with water,intended for absorbing the gas disengaged by the distillation. Thisapparatus will be more amply described in the latter part of this work.
Although we have not yet been able, either to compose or to decompoundthis acid of sea-salt, we cannot have the smallest doubt that it, likeall other acids, is composed by the union of oxygen with an acidifiablebase. We have therefore called this unknown substance the[Pg 72]muriaticbase, ormuriatic radical, deriving this name, after the example ofMr Bergman and Mr de Morveau, from the Latin wordmuria, which wasanciently used to signify sea-salt. Thus, without being able exactly todetermine the component parts ofmuriatic acid, we design, by thatterm, a volatile acid, which retains the form of gas in the commontemperature and pressure of our atmosphere, which combines with greatfacility, and in great quantity, with water, and whose acidifiable baseadheres so very intimately with oxygen, that no method has hitherto beendevised for separating them. If ever this acidifiable base of themuriatic acid is discovered to be a known substance, though now unknownin that capacity, it will be requisite to change its presentdenomination for one analogous with that of its base.
In common with sulphuric acid, and several other acids, the muriatic iscapable of different degrees of oxygenation; but the excess of oxygenproduces quite contrary effects upon it from what the same circumstanceproduces upon the acid of sulphur. The lower degree of oxygenationconverts sulphur into a volatile gasseous acid, which only mixes insmall proportions with water, whilst a higher oxygenation forms an acidpossessing much stronger acid properties, which is very fixed and cannotremain in the state of gas but in a very high temperature, which has[Pg 73] nosmell, and which mixes in large proportion with water. With muriaticacid, the direct reverse takes place; an additional saturation withoxygen renders it more volatile, of a more penetrating odour, lessmiscible with water, and diminishes its acid properties. We were atfirst inclined to have denominated these two degrees of saturation inthe same manner as we had done with the acid of sulphur, calling theless oxygenatedmuriatous acid, and that which is more saturated withoxygenmuriatic acid: But, as this latter gives very particularresults in its combinations, and as nothing analogous to it is yet knownin chemistry, we have left the name of muriatic acid to the lesssaturated, and give the latter the more compounded appellation ofoxygenated muriatic acid.
Although the base or radical of the acid which is extracted from nitreor saltpetre be better known, we have judged proper only to modify itsname in the same manner with that of the muriatic acid. It is drawn fromnitre, by the intervention of sulphuric acid, by a process similar tothat described for extracting the muriatic acid, and by means of thesame apparatus (Pl. IV. Fig. 1.). In proportion as the acid passes over,it is in part condensed in the baloon or recipient, and the rest isabsorbed by the water contained in the bottles L,L,L,L; the waterbecomes first green,[Pg 74] then blue, and at last yellow, in proportion tothe concentration of the acid. During this operation, a large quantityof oxygen gas, mixed with a small proportion of azotic gas, isdisengaged.
This acid, like all others, is composed of oxygen, united to anacidifiable base, and is even the first acid in which the existence ofoxygen was well ascertained. Its two constituent elements are but weaklyunited, and are easily separated, by presenting any substance with whichoxygen has a stronger affinity than with the acidifiable base peculiarto this acid. By some experiments of this kind, it was first discoveredthat azote, or the base of mephitis or azotic gas, constituted itsacidifiable base or radical; and consequently that the acid of nitre wasreally an azotic acid, having azote for its base, combined with oxygen.For these reasons, that we might be consistent with our principles, itappeared necessary, either to call the acid by the name ofazotic, orto name the basenitric radical; but from either of these we weredissuaded, by the following considerations. In thefirst place, itseemed difficult to change the name of nitre or saltpetre, which hasbeen universally adopted in society, in manufactures, and in chemistry;and, on the other hand, azote having been discovered by Mr Berthollet tobe the base of volatile alkali, or ammoniac, as well as of this acid,[Pg 75]we thought it improper to call it nitric radical. We have thereforecontinued the term of azote to the base of that part of atmospheric airwhich is likewise the nitric and ammoniacal radical; and we have namedthe acid of nitre, in its lower and higher degrees of oxygenation,nitrous acid in the former, andnitric acid in the latter state;thus preserving its former appellation properly modified.
Several very respectable chemists have disapproved of this deference forthe old terms, and wished us to have persevered in perfecting a newchemical language, without paying any respect for ancient usage; sothat, by thus steering a kind of middle course, we have exposedourselves to the censures of one sect of chemists, and to theexpostulations of the opposite party.
The acid of nitre is susceptible of assuming a great number of separatestates, depending upon its degree of oxygenation, or upon theproportions in which azote and oxygen enter into its composition. By afirst or lowest degree of oxygenation, it forms a particular species ofgas, which we shall continue to namenitrous gas; this is composednearly of two parts, by weight, of oxygen combined with one part ofazote; and in this state it is not miscible with water. In this gas, theazote is by no means saturated with oxygen, but, on the contrary, has[Pg 76]still a very great affinity for that element, and even attracts it fromatmospheric air, immediately upon getting into contact with it. Thiscombination of nitrous gas with atmospheric air has even become one ofthe methods for determining the quantity of oxygen contained in air, andconsequently for ascertaining its degree of salubrity.
This addition of oxygen converts the nitrous gas into a powerful acid,which has a strong affinity with water, and which is itself susceptibleof various additional degrees of oxygenation. When the proportions ofoxygen and azote is below three parts, by weight, of the former, to oneof the latter, the acid is red coloured, and emits copious fumes. Inthis state, by the application of a gentle heat, it gives out nitrousgas; and we term it, in this degree of oxygenation,nitrous acid. Whenfour parts, by weight, of oxygen, are combined with one part of azote,the acid is clear and colourless, more fixed in the fire than thenitrous acid, has less odour, and its constituent elements are morefirmly united. This species of acid, in conformity with our principlesof nomenclature, is callednitric acid.
Thus, nitric acid is the acid of nitre, surcharged with oxygen; nitrousacid is the acid of nitre surcharged with azote; or, what is the samething, with nitrous gas; and this latter is[Pg 77] azote not sufficientlysaturated with oxygen to possess the properties of an acid. To thisdegree of oxygenation, we have afterwards, in the course of this work,given the generical name ofoxyd[14].
[12] The term formerly used by the English chemists for thisacid was writtensulphureous; but we have thought proper to spell itas above, that it may better conform with the similar terminations ofnitrous, carbonous, &c. to be used hereafter. In general, we have usedthe English terminationsic andous to translate the terms of theAuthor which end withique andcux, with hardly any otheralterations.—E.
[13] For this purpose, the operation calleddecrepitation isused, which consists in subjecting it to nearly a red heat, in a propervessel, so as to evaporate all its water of crystallization.—E.
[14] In strict conformity with the principles of the newnomenclature, but which the Author has given his reasons for deviatingfrom in this instance, the following ought to have been the terms forazote, in its several degrees of oxygenation: Azote, azotic gas, (azotecombined with caloric), azotic oxyd gas, nitrous acid, and nitricacid.—E.
Oxygen has a stronger affinity with metals heated to a certain degreethan with caloric; in consequence of which, all metallic bodies,excepting gold, silver, and platina, have the property of decomposingoxygen gas, by attracting its base from the caloric with which it wascombined. We have already shown in what manner this decomposition takesplace, by means of mercury and iron; having observed, that, in the caseof the first, it must be considered as a kind of gradual combustion,whilst, in the latter, the combustion is extremely rapid, and attendedwith a brilliant flame. The use of the heat employed in these operationsis to separate the particles of the metal from each other, and todiminish their attraction of cohesion or aggregation, or, what is thesame thing, their mutual attraction for each other.
The absolute weight of metallic substances is augmented in proportion tothe quantity of oxygen they absorb; they, at the same time, lose theirmetallic splendour, and are reduced into[Pg 79] an earthy pulverulent matter.In this state metals must not be considered as entirely saturated withoxygen, because their action upon this element is counterbalanced by thepower of affinity between it and caloric. During the calcination ofmetals, the oxygen is therefore acted upon by two separate and oppositepowers, that of its attraction for caloric, and that exerted by themetal, and only tends to unite with the latter in consequence of theexcess of the latter over the former, which is, in general, veryinconsiderable. Wherefore, when metallic substances are oxygenated inatmospheric air, or in oxygen gas, they are not converted into acidslike sulphur, phosphorus, and charcoal, but are only changed intointermediate substances, which, though approaching to the nature ofsalts, have not acquired all the saline properties. The old chemistshave affixed the name ofcalx not only to metals in this state, but toevery body which has been long exposed to the action of fire withoutbeing melted. They have converted this wordcalx into a genericalterm, under which they confound calcareous earth, which, from a neutralsalt, which it really was before calcination, has been changed by fireinto an earthy alkali, bylosing half of its weight, with metalswhich, by the same means, have joined themselves to a new substance,whose quantity oftenexceeds half their weight, and by which they[Pg 80]have been changed almost into the nature of acids. This mode ofclassifying substances of so very opposite natures, under the samegeneric name, would have been quite contrary to our principles ofnomenclature, especially as, by retaining the above term for this stateof metallic substances, we must have conveyed very false ideas of itsnature. We have, therefore, laid aside the expressionmetallic calxaltogether, and have substituted in its place the termoxyd, from theGreek word οξυς.
By this may be seen, that the language we have adopted is both copiousand expressive. The first or lowest degree of oxygenation in bodies,converts them intooxyds; a second degree of additional oxygenationconstitutes the class of acids, of which the specific names, drawn fromtheir particular bases, terminate inous, as thenitrous andsulphurous acids; the third degree of oxygenation changes these intothe species of acids distinguished by the termination in ic, as thenitric andsulphuric acids; and, lastly, we can express a fourth, orhighest degree of oxygenation, by adding the wordoxygenated to thename of the acid, as has been already done with theoxygenatedmuriatic acid.
We have not confined the termoxyd to expressing the combinations ofmetals with oxygen, but have extended it to signify that first degree ofoxygenation in all bodies, which,[Pg 81] without converting them into acids,causes them to approach to the nature of salts. Thus, we give the nameofoxyd of sulphur to that soft substance into which sulphur isconverted by incipient combustion; and we call the yellow matter left byphosphorus, after combustion, by the name ofoxyd of phosphorus. Inthe same manner, nitrous gas, which is azote in its first degree ofoxygenation, is theoxyd of azote. We have likewise oxyds in greatnumbers from the vegetable and animal kingdoms; and I shall show, in thesequel, that this new language throws great light upon all theoperations of art and nature.
We have already observed, that almost all the metallic oxyds havepeculiar and permanent colours. These vary not only in the differentspecies of metals, but even according to the various degrees ofoxygenation in the same metal. Hence we are under the necessity ofadding two epithets to each oxyd, one of which indicates the metaloxydated[15], while the other indicates[Pg 82] the peculiar colour of theoxyd. Thus, we have the black oxyd of iron, the red oxyd of iron, andthe yellow oxyd of iron; which expressions respectively answer to theold unmeaning terms of martial ethiops, colcothar, and rust of iron, orochre. We have likewise the gray, yellow, and red oxyds of lead, whichanswer to the equally false or insignificant terms, ashes of lead,massicot, and minium.
These denominations sometimes become rather long, especially when wemean to indicate whether the metal has been oxydated in the air, bydetonation with nitre, or by means of acids; but then they always conveyjust and accurate ideas of the corresponding object which we wish toexpress by their use. All this will be rendered perfectly clear anddistinct by means of the tables which are added to this work.
[15] Here we see the word oxyd converted into the verbtooxydate,oxydated,oxydating, after the same manner with thederivation of the verbto oxygenate,oxygenated,oxygenating, fromthe wordoxygen. I am not clear of the absolute necessity of thissecond verb here first introduced, but think, in a work of this nature,that it is the duty of the translator to neglect every otherconsideration for the sake of strict fidelity to the ideas of hisauthor.—E.
Until very lately, water has always been thought a simple substance,insomuch that the older chemists considered it as an element. Such itundoubtedly was to them, as they were unable to decompose it; or, atleast, since the decomposition which took place daily before their eyeswas entirely unnoticed. But we mean to prove, that water is by no meansa simple or elementary substance. I shall not here pretend to give thehistory of this recent, and hitherto contested discovery, which isdetailed in the Memoirs of the Academy for 1781, but shall only bringforwards the principal proofs of the decomposition and composition ofwater; and, I may venture to say, that these will be convincing to suchas consider them impartially.
Having fixed the glass tube EF, (Pl. vii. fig. 11.) of from 8 to 12lines diameter, across a furnace, with a small inclination from E to F,[Pg 84]lute the superior extremity E to the glass retort A, containing adeterminate quantity of distilled water, and to the inferior extremityF, the worm SS fixed into the neck of the doubly tubulated bottle H,which has the bent tube KK adapted to one of its openings, in such amanner as to convey such aëriform fluids or gasses as may be disengaged,during the experiment, into a proper apparatus for determining theirquantity and nature.
To render the success of this experiment certain, it is necessary thatthe tube EF be made of well annealed and difficultly fusible glass, andthat it be coated with a lute composed of clay mixed with powderedstone-ware; besides which, it must be supported about its middle bymeans of an iron bar passed through the furnace, lest it should softenand bend during the experiment. A tube of China-ware, or porcellain,would answer better than one of glass for this experiment, were it notdifficult to procure one so entirely free from pores as to prevent thepassage of air or of vapours.
When things are thus arranged, a fire is lighted in the furnace EFCD,which is supported of such a strength as to keep the tube EF red hot,but not to make it melt; and, at the same time, such a fire is kept upin the furnace VVXX, as to keep the water in the retort A continuallyboiling.[Pg 85]
In proportion as the water in the retort A is evaporated, it fills thetube EF, and drives out the air it contained by the tube KK; the aqueousgas formed by evaporation is condensed by cooling in the worm SS, andfalls, drop by drop, into the tubulated bottle H. Having continued thisoperation until all the water be evaporated from the retort, and havingcarefully emptied all the vessels employed, we find that a quantity ofwater has passed over into the bottle H, exactly equal to what wasbefore contained in the retort A, without any disengagement of gaswhatsoever: So that this experiment turns out to be a simpledistillation; and the result would have been exactly the same, if thewater had been run from one vessel into the other, through the tube EF,without having undergone the intermediate incandescence.
The apparatus being disposed, as in the former experiment, 28grs. ofcharcoal, broken into moderately small parts, and which has previouslybeen exposed for a long time to a red heat in close vessels, areintroduced into the tube EF. Every thing else is managed as in thepreceding experiment.
The water contained in the retort A is distilled, as in the formerexperiment, and, being[Pg 86] condensed in the worm, falls into the bottle H;but, at the same time, a considerable quantity of gas is disengaged,which, escaping by the tube KK, is received in a convenient apparatusfor that purpose. After the operation is finished, we find nothing but afew atoms of ashes remaining in the tube EF; the 28grs. of charcoalhaving entirely disappeared.
When the disengaged gasses are carefully examined, they are sound toweigh 113.7grs.[16]; these are of two kinds, viz. 144 cubical inchesof carbonic acid gas, weighing 100grs. and 380 cubical inches of avery light gas, weighing only 13.7grs. which takes fire when incontact with air, by the approach of a lighted body; and, when the waterwhich has passed over into the bottle H is carefully examined, it isfound to have lost 85.7grs. of its weight. Thus, in this experiment,85.7grs. of water, joined to 28grs. of charcoal, have combined insuch a way as to form 100grs. of carbonic acid, and 13.7grs. of aparticular gas capable of being burnt.
I have already shown, that 100grs. of carbonic acid gas consists of72grs. of oxygen, combined with 28grs. of charcoal; hence the 28[Pg 87]grs. of charcoal placed in the glass tube have acquired 72grs. ofoxygen from the water; and it follows, that 85.7grs. of water arecomposed of 72grs. of oxygen, combined with 13.7grs. of a gassusceptible of combustion. We shall see presently that this gas cannotpossibly have been disengaged from the charcoal, and must, consequently,have been produced from the water.
I have suppressed some circumstances in the above account of thisexperiment, which would only have complicated and obscured its resultsin the minds of the reader. For instance, the inflammable gas dissolvesa very small part of the charcoal, by which means its weight is somewhataugmented, and that of the carbonic gas proportionally diminished.Altho' the alteration produced by this circumstance is veryinconsiderable; yet I have thought it necessary to determine its effectsby rigid calculation, and to report, as above, the results of theexperiment in its simplified state, as if this circumstance had nothappened. At any rate, should any doubts remain respecting theconsequences I have drawn from this experiment, they will be fullydissipated by the following experiments, which I am going to adduce insupport of my opinion.[Pg 88]
The apparatus being disposed exactly as in the former experiment, withthis difference, that instead of the 28grs. of charcoal, the tube EFis filled with 274grs. of soft iron in thin plates, rolled upspirally. The tube is made red hot by means of its furnace, and thewater in the retort A is kept constantly boiling till it be allevaporated, and has passed through the tube EF, so as to be condensed inthe bottle H.
No carbonic acid gas is disengaged in this experiment, instead of whichwe obtain 416 cubical inches, or 15grs. of inflammable gas, thirteentimes lighter than atmospheric air. By examining the water which hasbeen distilled, it is found to have lost 100grs. and the 274grs.of iron confined in the tube are found to have acquired 85grs.additional weight, and its magnitude is considerably augmented. The ironis now hardly at all attractable by the magnet; it dissolves in acidswithout effervescence; and, in short, it is converted into a black oxyd,precisely similar to that which has been burnt in oxygen gas.
In this experiment we have a trueoxydation of iron, by means ofwater, exactly similar to that produced in air by the assistance ofheat. One hundred grains of water having been decomposed,[Pg 89] 85grs. ofoxygen have combined with the iron, so as to convert it into the stateof black oxyd, and 15grs. of a peculiar inflammable gas aredisengaged: From all this it clearly follows, that water is composed ofoxygen combined with the base of an inflammable gas, in the respectiveproportions of 85 parts, by weight of the former, to 15 parts of thelatter.
Thus water, besides the oxygen, which is one of its elements in commonwith many other substances, contains another element as its constituentbase or radical, and for which we must find an appropriate term. Nonethat we could think of seemed better adapted than the wordhydrogen,which signifies thegenerative principle of water, from υδορaqua, and γεινομαςgignor[17]. We call the combination ofthis element with calorichydrogen gas; and the term hydrogenexpresses the base of that gas, or the radical of water.
This experiment furnishes us with a new combustible body, or, in otherwords, a body which has so much affinity with oxygen as to draw it fromits connection with caloric, and to decompose air or oxygen gas. Thiscombustible body has itself so great affinity with caloric, that, unlesswhen engaged in a combination with some other body, it always subsistsin the aëriform or gasseous state, in the usual temperature and pressureof our atmosphere. In this state of gas it is about 1/13 of the weightof an equal bulk of atmospheric air; it is not absorbed by water, thoughit is capable of holding a small quantity of that fluid in solution, andit is incapable of being used for respiration.
As the property this gas possesses, in common with all other combustiblebodies, is nothing more than the power of decomposing air, and carryingoff its oxygen from the caloric with which it was combined, it is easilyunderstood that it cannot burn, unless in contact with air or oxygengas. Hence, when we set fire to a bottle full of this gas, it burnsgently, first at the neck of the bottle, and then in the inside of it,in proportion as the external air gets in: This combustion is slow andsuccessive, and only takes place at the surface of contact between thetwo gasses. It is quite different when the two gasses are mixed beforethey are set on fire: If, for instance, after having introduced one partof[Pg 91] oxygen gas into a narrow mouthed bottle, we fill it up with twoparts of hydrogen gas, and bring a lighted taper, or other burning body,to the mouth of the bottle, the combustion of the two gasses takes placeinstantaneously with a violent explosion. This experiment ought only tobe made in a bottle of very strong green glass, holding not more than apint, and wrapped round with twine, otherwise the operator will beexposed to great danger from the rupture of the bottle, of which thefragments will be thrown about with great force.
If all that has been related above, concerning the decomposition ofwater, be exactly conformable to truth;—if, as I have endeavoured toprove, that substance be really composed of hydrogen, as its properconstituent element, combined with oxygen, it ought to follow, that, byreuniting these two elements together, we should recompose water; andthat this actually happens may be judged of by the following experiment.
I took a large cristal baloon, A, Pl. iv. fig. 5. holding about 30pints, having a large opening, to which was cemented the plate of copperBC, pierced with four holes, in which four tubes terminate. The firsttube, H h, is intended to[Pg 92] be adapted to an air pump, by which thebaloon is to be exhausted of its air. The second tube gg, communicates,by its extremity MM, with a reservoir of oxygen gas, with which thebaloon is to be filled. The third tube d D d', communicates, by itsextremity d NN, with a reservoir of hydrogen gas. The extremity d' ofthis tube terminates in a capillary opening, through which the hydrogengas contained in the reservoir is forced, with a moderate degree ofquickness, by the pressure of one or two inches of water. The fourthtube contains a metallic wire GL, having a knob at its extremity L,intended for giving an electrical spark from L to d', on purpose to setfire to the hydrogen gas: This wire is moveable in the tube, that we maybe able to separate the knob L from the extremity d' of the tube D d'.The three tubes d D d', gg, and H h, are all provided with stop-cocks.
That the hydrogen gas and oxygen gas may be as much as possible deprivedof water, they are made to pass, in their way to the baloon A, throughthe tubes MM, NN, of about an inch diameter, and filled with salts,which, from their deliquescent nature, greedily attract the moisture ofthe air: Such are the acetite of potash, and the muriat or nitrat oflime[18]. These salts[Pg 93] must only be reduced to a coarse powder, lestthey run into lumps, and prevent the gasses from geting through theirinterstices.
We must be provided before hand with a sufficient quantity of oxygengas, carefully purified from all admixture of carbonic acid, by longcontact with a solution of potash[19].
We must likewise have a double quantity of hydrogen gas, carefullypurified in the same manner by long contact with a solution of potash inwater. The best way of obtaining this gas free from mixture is, bydecomposing water with very pure soft iron, as directed in Exp. 3. ofthis chapter.
Having adjusted every thing properly, as above directed, the tube H h isadapted to an air-pump, and the baloon A is exhausted of its air. Wenext admit the oxygen gas so as to fill the baloon, and then, by meansof pressure, as is before mentioned, force a small stream of hydrogengas through its tube D d', which we immediately set on fire by anelectric spark. By means of the above described apparatus, we can[Pg 94]continue the mutual combustion of these two gasses for a long time, aswe have the power of supplying them to the baloon from their reservoirs,in proportion as they are consumed. I have in another place[20] given adescription of the apparatus used in this experiment, and have explainedthe manner of ascertaining the quantities of the gasses consumed withthe most scrupulous exactitude.
In proportion to the advancement of the combustion, there is adeposition of water upon the inner surface of the baloon or matrass A:The water gradually increases in quantity, and, gathering into largedrops, runs down to the bottom of the vessel. It is easy to ascertainthe quantity of water collected, by weighing the baloon both before andafter the experiment. Thus we have a twofold verification of ourexperiment, by ascertaining both the quantities of the gasses employed,and of the water formed by their combustion: These two quantities mustbe equal to each other. By an operation of this kind, Mr Meusnier and Iascertained that it required 85 parts, by weight, of oxygen, united to15 parts of hydrogen, to compose 100 parts of water. This experiment,which has not hitherto been published, was made in presence of anumerous committee from the Royal Academy.[Pg 95] We exerted the mostscrupulous attention to its accuracy; and have reason to believe thatthe above propositions cannot vary a two hundredth part from absolutetruth.
From these experiments, both analytical and synthetic, we may now affirmthat we have ascertained, with as much certainty as is possible inphysical or chemical subjects, that water is not a simple elementarysubstance, but is composed of two elements, oxygen and hydrogen; whichelements, when existing separately, have so strong affinity for caloric,as only to subsist under the form of gas in the common temperature andpressure of our atmosphere.
This decomposition and recomposition of water is perpetually operatingbefore our eyes, in the temperature of the atmosphere, by means ofcompound elective attraction. We shall presently see that the phenomenaattendant upon vinous fermentation, putrefaction, and even vegetation,are produced, at least in a certain degree, by decomposition of water.It is very extraordinary that this fact should have hitherto beenoverlooked by natural philosophers and chemists: Indeed, it stronglyproves, that, in chemistry, as in moral philosophy, it is extremelydifficult to overcome prejudices imbibed in early education, and tosearch for truth in any other road than the one we have been accustomedto follow.[Pg 96]
I shall finish this chapter by an experiment much less demonstrativethan those already related, but which has appeared to make moreimpression than any other upon the minds of many people. When 16 ouncesof alkohol are burnt in an apparatus[21] properly adapted for collectingall the water disengaged during the combustion, we obtain from 17 to 18ounces of water. As no substance can furnish a product larger than itsoriginal bulk, it follows, that something else has united with thealkohol during its combustion; and I have already shown that this mustbe oxygen, or the base of air. Thus alkohol contains hydrogen, which isone of the elements of water; and the atmospheric air contains oxygen,which is the other element necessary to the composition of water. Thisexperiment is a new proof that water is a compound substance.
[16] In the latter part of this work will be found a particularaccount of the processes necessary for separating the different kinds ofgasses, and for determining their quantities.—A.
[17] This expression Hydrogen has been very severely criticisedby some, who pretend that it signifies engendered by water, and not thatwhich engenders water. The experiments related in this chapter prove,that, when water is decomposed, hydrogen is produced, and that, whenhydrogen is combined with oxygen, water is produced: So that we may say,with equal truth, that water is produced from hydrogen, or hydrogen isproduced from water.—A.
[18] See the nature of these salts in the second part of thisbook.—A.
[19] By potash is here meant, pure or caustic alkali, deprivedof carbonic acid by means of quick-lime: In general, we may observehere, that all the alkalies and earths must invariably be considered asin their pure or caustic state, unless otherwise expressed.—E. Themethod of obtaining this pure alkali of potash will be given in thesequel.—A.
[20] See the third part of this work.—A.
[21] See an account of this apparatus in the third part of thiswork.—A.
We have already mentioned, that, when any body is burnt in the center ofa hollow sphere of ice and supplied with air at the temperature of zero(32°), the quantity of ice melted from the inside of the sphere becomesa measure of the relative quantities of caloric disengaged. Mr de laPlace and I gave a description of the apparatus employed for this kindof experiment in the Memoirs of the Academy for 1780, p. 355; and adescription and plate of the same apparatus will be found in the thirdpart of this work. With this apparatus, phosphorus, charcoal, andhydrogen gas, gave the following results:
One pound of phosphorus melted 100libs. of ice.
One pound of charcoal melted 96libs. 8oz.
One pound of hydrogen gas melted 295libs. 9oz. 3-1/2gros.
As a concrete acid is formed by the combustion of phosphorus, it isprobable that very little caloric remains in the acid, and,consequently,[Pg 98] that the above experiment gives us very nearly the wholequantity of caloric contained in the oxygen gas. Even if we suppose thephosphoric acid to contain a good deal of caloric, yet, as thephosphorus must have contained nearly an equal quantity beforecombustion, the error must be very small, as it will only consist of thedifference between what was contained in the phosphorus before, and inthe phosphoric acid after combustion.
I have already shown in Chap. V. that one pound of phosphorus absorbsone pound eight ounces of oxygen during combustion; and since, by thesame operation, 100lib. of ice are melted, it follows, that thequantity of caloric contained in one pound of oxygen gas is capable ofmelting 66 libs. 10oz. 5gros 24grs. of ice.
One pound of charcoal during combustion melts only 96libs. 8oz. ofice, whilst it absorbs 2libs. 9oz. 1gros 10grs. of oxygen.By the experiment with phosphorus, this quantity of oxygen gas ought todisengage a quantity of caloric sufficient to melt 171libs. 6oz. 5gros of ice; consequently, during this experiment, a quantity ofcaloric, sufficient to melt 74libs. 14oz. 5gros of icedisappears. Carbonic acid is not, like phosphoric acid, in a concretestate after combustion but in the state of gas, and requires to beunited with caloric to enable it to[Pg 99] subsist in that state; the quantityof caloric missing in the last experiment is evidently employed for thatpurpose. When we divide that quantity by the weight of carbonic acid,formed by the combustion of one pound of charcoal, we find that thequantity of caloric necessary for changing one pound of carbonic acidfrom the concrete to the gasseous state, would be capable of melting 20libs. 15oz. 5gros of ice.
We may make a similar calculation with the combustion of hydrogen gasand the consequent formation of water. During the combustion of onepound of hydrogen gas, 5libs. 10oz. 5gros 24grs. of oxygengas are absorbed, and 295libs. 9oz. 3-1/2gros of ice aremelted. But 5libs. 10oz. 5gros 24grs. of oxygen gas, inchanging from the aëriform to the solid state, loses, according to theexperiment with phosphorus, enough of caloric to have melted 377libs.12oz. 3gros of ice. There is only disengaged, from the samequantity of oxygen, during its combustion with hydrogen gas, as muchcaloric as melts 295libs. 2oz. 3-1/2gros; wherefore thereremains in the water at Zero (32°), formed, during this experiment, asmuch caloric as would melt 82libs. 9oz. 7-1/2gros of ice.
Hence, as 6libs. 10oz. 5gros 24grs. of water are formed fromthe combustion of one pound of hydrogen gas with 5libs. 10oz. 5gros 24grs. of oxygen, it follows that, in each[Pg 100] pound of water, atthe temperature of Zero, (32°), there exists as much caloric as wouldmelt 12libs. 5oz. 2gros 48grs. of ice, without taking intoaccount the quantity originally contained in the hydrogen gas, which wehave been obliged to omit, for want of data to calculate its quantity.From this it appears that water, even in the state of ice, contains aconsiderable quantity of caloric, and that oxygen, in entering into thatcombination, retains likewise a good proportion.
From these experiments, we may assume the following results assufficiently established.
From the combustion of phosphorus, as related in the foregoingexperiments, it appears, that one pound of phosphorus requires 1lib.8oz. of oxygen gas for its combustion, and that 2libs. 8oz. ofconcrete phosphoric acid are produced.
| The quantity of caloric disengaged by the combustion of one pound of phosphorus, expressed by the number of pounds of ice melted during that operation, is | 100.00000. |
| The quantity disengaged from each pound of oxygen, during the combustion of phosphorus, expressed in the same manner, is | 66.66667. |
| The quantity disengaged during the formation of one pound of phosphoric acid, | 40.00000. |
| The quantity remaining in each pound of phosphoric acid, | 0.00000(A). |
[Note A: We here suppose the phosphoric acid not to contain any caloric,which is not strictly true; but, as I have before observed, the quantityit really contains is probably very small, and we have not given it avalue, for want of a sufficient data to go upon.—A.][Pg 101]
In the combustion of one pound of charcoal, 2libs. 9oz. 1gros10grs. of oxygen gas are absorbed, and 3libs. 9oz. 1gros 10grs. of carbonic acid gas are formed.
| Caloric, disengaged daring the combustion of one pound of charcoal, | 96.50000(A). |
| Caloric disengaged during the combustion of charcoal, from each pound of oxygen gas absorbed, | 37.52823. |
| Caloric disengaged during the formation of one pound of carbonic acid gas, | 27.02024. |
| Caloric retained by each pound of oxygen after the combustion, | 29.13844. |
| Caloric necessary for supporting one pound of carbonic acid in the state of gas, | 20.97960. |
[Note A: All these relative quantities of caloric are expressed by thenumber of pounds of ice, and decimal parts, melted during the severaloperations.—E.][Pg 102]
In the combustion of one pound of hydrogen gas, 5libs. 10oz. 5gros 24grs. of oxygen gas are absorbed, and 6libs. 10oz. 5gros 24grs. of water are formed.
| Caloric from eachlib. of hydrogen gas, | 295.58950. |
| Caloric from eachlib. of oxygen gas, | 52.16280. |
| Caloric disengaged during the formation of each pound of water, | 44.33840. |
| Caloric retained by eachlib. of oxygen after combustion with hydrogen, | 14.50386. |
| Caloric retained by eachlib. of water at the temperature of Zero (32°), | 12.32823. |
When we combine nitrous gas with oxygen gas, so as to form nitric ornitrous acid a degree of heat is produced, which is much lessconsiderable than what is evolved during the other combinations ofoxygen; whence it follows that oxygen, when it becomes fixed in nitricacid, retains a great part of the heat which it possessed[Pg 103] in the stateof gas. It is certainly possible to determine the quantity of caloricwhich is disengaged during the combination of these two gasses, andconsequently to determine what quantity remains after the combinationtakes place. The first of these quantities might be ascertained, bymaking the combination of the two gasses in an apparatus surrounded byice; but, as the quantity of caloric disengaged is very inconsiderable,it would be necessary to operate upon a large quantity of the two gassesin a very troublesome and complicated apparatus. By this consideration,Mr de la Place and I have hitherto been prevented from making theattempt. In the mean time, the place of such an experiment may besupplied by calculations, the results of which cannot be very far fromtruth.
Mr de la Place and I deflagrated a convenient quantity of nitre andcharcoal in an ice apparatus, and found that twelve pounds of ice weremelted by the deflagration of one pound of nitre. We shall see, in thesequel, that one pound of nitre is composed, as under, of
| Potash | 7oz. | 6gros | 51.84grs. | = | 4515.84grs. |
| Dry acid | 8 | 1 | 21.16 | = | 4700.16. |
The above quantity of dry acid is composed of[Pg 104]
| Oxygen | 6oz. | 3gros | 66.34grs. | = | 3738.34grs. |
| Azote | 1 | 5 | 25.82 | = | 961.82. |
By this we find that, during the above deflagration, 2gros 1-1/3gr. of charcoal have suffered combustion, alongst with 3738.34grs.or 6oz. 3gros 66.34grs. of oxygen. Hence, since 12libs. ofice were melted during the combustion, it follows, that one pound ofoxygen burnt in the same manner would have melted 29.58320libs. ofice. To which the quantity of caloric, retained by a pound of oxygenafter combining with charcoal to form carbonic acid gas, being added,which was already ascertained to be capable of melting 29.13844libs.of ice, we have for the total quantity of caloric remaining in a poundof oxygen, when combined with nitrous gas in the nitric acid 58.72164;which is the number of pounds of ice the caloric remaining in the oxygenin that state is capable of melting.
We have before seen that, in the state of oxygen gas, it contained atleast 66.66667; wherefore it follows that, in combining with azote toform nitric acid, it only loses 7.94502. Farther experiments upon thissubject are necessary to ascertain how far the results of thiscalculation may agree with direct fact. This enormous quantity ofcaloric retained by oxygen in its combination into nitric acid, explainsthe[Pg 105] cause of the great disengagement of caloric during thedeflagrations of nitre; or, more strictly speaking, upon all occasionsof the decomposition of nitric acid.
Having examined several cases of simple combustion, I mean now to give afew examples of a more complex nature. One pound of wax-taper beingallowed to burn slowly in an ice apparatus, melted 133libs. 2oz.5-1/3gros of ice. According to my experiments in the Memoirs of theAcademy for 1784, p. 606, one pound of wax-taper consists of 13oz. 1gros 23grs. of charcoal, and 2oz. 6gros 49grs. ofhydrogen.
| By the foregoing experiments, the above quantity of charcoal ought to melt | 79.39390libs. of ice; |
| and the hydrogen should melt | 52.37605 |
| ———— | |
| In all | 131.76995libs. |
Thus, we see the quantity of caloric disengaged from a burning taper, ispretty exactly conformable to what was obtained by burning separately aquantity of charcoal and hydrogen[Pg 106] equal to what enters into itscomposition. These experiments with the taper were several timesrepeated, so that I have reason to believe them accurate.
We included a burning lamp, containing a determinate quantity ofolive-oil, in the ordinary apparatus, and, when the experiment wasfinished, we ascertained exactly the quantities of oil consumed, and ofice melted; the result was, that, during the combustion of one pound ofolive-oil, 148libs. 14oz. 1gros of ice were melted. By myexperiments in the Memoirs of the Academy for 1784, and of which thefollowing Chapter contains an abstract, it appears that one pound ofolive-oil consists of 12oz. 5gros 5grs. of charcoal, and 3oz. 2gros 67grs. of hydrogen. By the foregoing experiments, thatquantity of charcoal should melt 76.18723libs. of ice, and thequantity of hydrogen in a pound of the oil should melt 62.15053libs.The sum of these two gives 138.33776libs. of ice, which the twoconstituent elements of the oil would have melted, had they separatelysuffered combustion, whereas the oil really melted 148.88330libs.which gives an excess of 10.54554 in the result of the experiment[Pg 107] abovethe calculated result, from data furnished by former experiments.
This difference, which is by no means very considerable, may arise fromerrors which are unavoidable in experiments of this nature, or it may beowing to the composition of oil not being as yet exactly ascertained. Itproves, however, that there is a great agreement between the results ofour experiments, respecting the combination of caloric, and those whichregard its disengagement.
The following desiderata still remain to be determined, viz. Whatquantity of caloric is retained by oxygen, after combining with metals,so as to convert them into oxyds; What quantity is contained byhydrogen, in its different states of existence; and to ascertain, withmore precision than is hitherto attained, how much caloric is disengagedduring the formation of water, as there still remain considerable doubtswith respect to our present determination of this point, which can onlybe removed by farther experiments. We are at present occupied with thisinquiry; and, when once these several points are well ascertained, whichwe hope they will soon be, we shall probably be under the necessity ofmaking considerable corrections upon most of the results of theexperiments and calculations in this Chapter. I did not, however,consider this as a sufficient reason for withholding[Pg 108] so much as isalready known from such as may be inclined to labour upon the samesubject. It is difficult, in our endeavours to discover the principlesof a new science, to avoid beginning by guess-work; and it is rarelypossible to arrive at perfection from the first setting out.
As combustible substances in general have a great affinity for oxygen,they ought likewise to attract, or tend to combine with each other;quae sunt eadem uni tertio, sunt eadem inter se; and the axiom isfound to be true. Almost all the metals, for instance, are capable ofuniting with each other, and forming what are calledalloys[22], incommon language. Most of these, like all combinations, are susceptibleof several degrees of saturation; the greater number of these alloys aremore brittle than the pure metals of which they are composed, especiallywhen the metals alloyed together are considerably different in theirdegrees of fusibility. To this difference in fusibility, part of thephenomena attendant uponalloyage are owing, particularly the propertyof iron, called by workmen[Pg 110]hotshort. This kind of iron must beconsidered as an alloy, or mixture of pure iron, which is almostinfusible, with a small portion of some other metal which fuses in amuch lower degree of heat. So long as this alloy remains cold, and bothmetals are in the solid state, the mixture is malleable; but, if heatedto a sufficient degree to liquify the more fusible metal, the particlesof the liquid metal, which are interposed between the particles of themetal remaining solid, must destroy their continuity, and occasion thealloy to become brittle. The alloys of mercury, with the other metals,have usually been calledamalgams, and we see no inconvenience fromcontinuing the use of that term.
Sulphur, phosphorus, and charcoal, readily unite with metals.Combinations of sulphur with metals are usually namedpyrites. Theircombinations with phosphorus and charcoal are either not yet named, orhave received new names only of late; so that we have not scrupled tochange them according to our principles. The combinations of metal andsulphur we callsulphurets, those with phosphorusphosphurets, andthose formed with charcoalcarburets. These denominations are extendedto all the combinations into which the above three substances enter,without being previously oxygenated.[Pg 111] Thus, the combination of sulphurwith potash, or fixed vegetable alkali, is calledsulphuret of potash;that which it forms with ammoniac, or volatile alkali, is termedsulphuret of ammoniac.
Hydrogen is likewise capable of combining with many combustiblesubstances. In the state of gas, it dissolves charcoal, sulphur,phosphorus, and several metals; we distinguish these combinations by theterms,carbonated hydrogen gas,sulphurated hydrogen gas, andphosphorated hydrogen gas. The sulphurated hydrogen gas was calledhepatic air by former chemists, orfoetid air from sulphur, by MrScheele. The virtues of several mineral waters, and the foetid smell ofanimal excrements, chiefly arise from the presence of this gas. Thephosphorated hydrogen gas is remarkable for the property, discovered byMr Gengembre, of taking fire spontaneously upon getting into contactwith atmospheric air, or, what is better, with oxygen gas. This gas hasa strong flavour, resembling that of putrid fish; and it is veryprobable that the phosphorescent quality of fish, in the state ofputrefaction, arises from the escape of this species of gas. Whenhydrogen and charcoal are combined together, without the intervention ofcaloric, to bring the hydrogen into the state of gas, they form oil,which is either fixed or volatile, according to the proportions ofhydrogen and[Pg 112] charcoal in its composition. The chief difference betweenfixed or fat oils drawn from vegetables by expression, and volatile oressential oils, is, that the former contains an excess of charcoal,which is separated when the oils are heated above the degree of boilingwater; whereas the volatile oils, containing a just proportion of thesetwo constituent ingredients, are not liable to be decomposed by thatheat, but, uniting with caloric into the gasseous state, pass over indistillation unchanged.
In the Memoirs of the Academy for 1784, p. 593. I gave an account of myexperiments upon the composition of oil and alkohol, by the union ofhydrogen with charcoal, and of their combination with oxygen. By theseexperiments, it appears that fixed oils combine with oxygen duringcombustion, and are thereby converted into water and carbonic acid. Bymeans of calculation applied to the products of these experiments, wefind that fixed oil is composed of 21 parts, by weight, of hydrogencombined with 79 parts of charcoal. Perhaps the solid substances of anoily nature, such as wax, contain a proportion of oxygen, to which theyowe their state of solidity. I am at present engaged in a series ofexperiments, which I hope will throw great light upon this subject.
It is worthy of being examined, whether hydrogen in its concrete state,uncombined with[Pg 113] caloric, be susceptible of combination with sulphur,phosphorus, and the metals. There is nothing that we know of, which,apriori, should render these combinations impossible; for combustiblebodies being in general susceptible of combination with each other,there is no evident reason for hydrogen being an exception to the rule:However, no direct experiment as yet establishes either the possibilityor impossibility of this union. Iron and zinc are the most likely, ofall the metals, for entering into combination with hydrogen; but, asthese have the property of decomposing water, and as it is verydifficult to get entirely free from moisture in chemical experiments, itis hardly possible to determine whether the small portions of hydrogengas, obtained in certain experiments with these metals, were previouslycombined with the metal in the state of solid hydrogen, or if they wereproduced by the decomposition of a minute quantity of water. The morecare we take to prevent the presence of water in these experiments, theless is the quantity of hydrogen gas procured; and, when very accurateprecautions are employed, even that quantity becomes hardly sensible.
However this inquiry may turn out respecting the power of combustiblebodies, as sulphur, phosphorus, and metals, to absorb hydrogen, we arecertain that they only absorb a very small[Pg 114] portion; and that thiscombination, instead of being essential to their constitution, can onlybe considered as a foreign substance, which contaminates their purity.It is the province of the advocates[23] for this system to prove, bydecisive experiments, the real existence of this combined hydrogen,which they have hitherto only done by conjectures founded uponsuppositions.
[22] This termalloy, which we have from the language of thearts, serves exceedingly well for distinguishing all the combinations orintimate unions of metals with each other, and is adopted in our newnomenclature for that purpose.—A.
[23] By these are meant the supporters of the phlogistictheory, who at present consider hydrogen, or the base of inflammableair, as the phlogiston of the celebrated Stahl.—E.
We have, in Chap. V. and VIII. examined the products resulting from thecombustion of the four simple combustible substances, sulphur,phosphorus, charcoal, and hydrogen: We have shown, in Chap. X that thesimple combustible substances are capable of combining with each otherinto compound combustible substances, and have observed that oils ingeneral, and particularly the fixed vegetable oils, belong to thisclass, being composed of hydrogen and charcoal. It remains, in thischapter, to treat of the oxygenation of these compound combustiblesubstances, and to show that there exist acids and oxyds having doubleand triple bases. Nature furnishes us with numerous examples of thiskind of combinations, by means of which, chiefly, she is enabled toproduce a vast variety of compounds from a very limited number ofelements, or simple substances.[Pg 116]
It was long ago well known, that, when muriatic and nitric acids weremixed together, a compound acid was formed, having properties quitedistinct from those of either of the acids taken separately. This acidwas calledaqua regia, from its most celebrated property of dissolvinggold, calledking of metals by the alchymists. Mr Berthollet hasdistinctly proved that the peculiar properties of this acid arise fromthe combined action of its two acidifiable bases; and for this reason wehave judged it necessary to distinguish it by an appropriate name: Thatofnitro-muriatic acid appears extremely applicable, from itsexpressing the nature of the two substances which enter into itscomposition.
This phenomenon of a double base in one acid, which had formerly beenobserved only in the nitro-muriatic acid, occurs continually in thevegetable kingdom, in which a simple acid, or one possessed of a singleacidifiable base, is very rarely found. Almost all the acids procurablefrom this kingdom have bases composed of charcoal and hydrogen, or ofcharcoal, hydrogen, and phosphorus, combined with more or less oxygen.All these bases, whether double or triple, are likewise formed intooxyds, having less oxygen than is necessary to give them the propertiesof acids. The acids and oxyds from the animal kingdom are still morecompound, as their bases generally consist of a combination[Pg 117] ofcharcoal, phosphorus, hydrogen, and azote.
As it is but of late that I have acquired any clear and distinct notionsof these substances, I shall not, in this place, enlarge much upon thesubject, which I mean to treat of very fully in some memoirs I ampreparing to lay before the Academy. Most of my experiments are alreadyperformed; but, to be able to give exact reports of the resultingquantities, it is necessary that they be carefully repeated, andincreased in number: Wherefore, I shall only give a short enumeration ofthe vegetable and animal acids and oxyds, and terminate this article bya few reflections upon the composition of vegetable and animal bodies.
Sugar, mucus, under which term we include the different kinds of gums,and starch, are vegetable oxyds, having hydrogen and charcoal combined,in different proportions, as their radicals or bases, and united withoxygen, so as to bring them to the state of oxyds. From the state ofoxyds they are capable of being changed into acids by the addition of afresh quantity of oxygen; and, according to the degrees of oxygenation,and the proportion of hydrogen and charcoal in their bases, they formthe several kinds of vegetable acids.
It would be easy to apply the principles of our nomenclature to givenames to these vegetable[Pg 118] acids and oxyds, by using the names of the twosubstances which compose their bases: They would thus becomehydro-carbonous acids and oxyds: In this method we might indicate whichof their elements existed in excess, without circumlocution, after themanner used by Mr Rouelle for naming vegetable extracts: He calls theseextracto-resinous when the extractive matter prevails in theircomposition, and resino-extractive when they contain a larger proportionof resinous matter. Upon that plan, and by varying the terminationsaccording to the formerly established rules of our nomenclature, we havethe following denominations: Hydro-carbonous, hydro-carbonic;carbono-hydrous, and carbono-hydric oxyds. And for the acids:Hydro-carbonous, hydro carbonic, oxygenated hydro-carbonic;carbono-hydrous, carbono-hydric, and oxygenated carbono-hydric. It isprobable that the above terms would suffice for indicating all thevarieties in nature, and that, in proportion as the vegetable acidsbecome well understood, they will naturally arrange themselves underthese denominations. But, though we know the elements of which these arecomposed, we are as yet ignorant of the proportions of theseingredients, and are still far from being able to class them in theabove methodical manner; wherefore, we have determined to retain[Pg 119] theancient names provisionally. I am somewhat farther advanced in thisinquiry than at the time of publishing our conjunct essay upon chemicalnomenclature; yet it would be improper to draw decided consequences fromexperiments not yet sufficiently precise: Though I acknowledge that thispart of chemistry still remains in some degree obscure, I must expressmy expectations of its being very soon elucidated.
I am still more forcibly necessitated to follow the same plan in namingthe acids, which have three or four elements combined in their bases; ofthese we have a considerable number from the animal kingdom, and someeven from vegetable substances. Azote, for instance, joined to hydrogenand charcoal, form the base or radical of the Prussic acid; we havereason to believe that the same happens with the base of the Gallicacid; and almost all the animal acids have their bases composed ofazote, phosphorus, hydrogen, and charcoal. Were we to endeavour toexpress at once all these four component parts of the bases, ournomenclature would undoubtedly be methodical; it would have the propertyof being clear and determinate; but this assemblage of Greek and Latinsubstantives and adjectives, which are not yet universally admitted bychemists, would have the appearance of a[Pg 120] barbarous language, difficultboth to pronounce and to be remembered. Besides, this part of chemistrybeing still far from that accuracy it must arrive to, the perfection ofthe science ought certainly to precede that of its language; and we muststill, for some time, retain the old names for the animal oxyds andacids. We have only ventured to make a few slight modifications of thesenames, by changing the termination intoous, when we have reason tosuppose the base to be in excess, and intoic, when we suspect theoxygen predominates.
The following are all the vegetable acids hitherto known:
Though all these acids, as has been already said, are chiefly, andalmost entirely, composed of hydrogen, charcoal, and oxygen, yet,properly speaking, they contain neither water carbonic acid nor oil, butonly the elements necessary for forming these substances. The power ofaffinity reciprocally exerted by the hydrogen, charcoal, and oxygen, inthese acids, is in a state[Pg 121] of equilibrium only capable of existing inthe ordinary temperature of the atmosphere; for, when they are heatedbut a very little above the temperature of boiling water, thisequilibrium is destroyed, part of the oxygen and hydrogen unite, andform water; part of the charcoal and hydrogen combine into oil; part ofthe charcoal and oxygen unite to form carbonic acid; and, lastly, theregenerally remains a small portion of charcoal, which, being in excesswith respect to the other ingredients, is left free. I mean to explainthis subject somewhat farther in the succeeding chapter.
The oxyds of the animal kingdom are hitherto less known than those fromthe vegetable kingdom, and their number is as yet not at all determined.The red part of the blood, lymph, and most of the secretions, are trueoxyds, under which point of view it is very important to consider them.We are only acquainted with six animal acids, several of which, it isprobable, approach very near each other in their nature, or, at least,differ only in a scarcely sensible degree. I do not include thephosphoric acid amongst these, because it is found in all the kingdomsof nature. They are,
The connection between the constituent elements of the animal oxyds andacids is not more permanent than in those from the vegetable kingdom, asa small increase of temperature is sufficient to overturn it. I hope torender this subject more distinct than has been done hitherto in thefollowing chapter.
Before we can thoroughly comprehend what takes place during thedecomposition of vegetable substances by fire, we must take intoconsideration the nature of the elements which enter into theircomposition, and the different affinities which the particles of theseelements exert upon each other, and the affinity which caloric possesseswith them. The true constituent elements of vegetables are hydrogen,oxygen, and charcoal: These are common to all vegetables, and novegetable can exist without them: Such other substances as exist inparticular vegetables are only essential to the composition of those inwhich they are found, and do not belong to vegetables in general.
Of these elements, hydrogen and oxygen have a strong tendency to unitewith caloric, and be converted into gas, whilst charcoal is a fixedelement, having but little affinity with caloric. On the other hand,oxygen, which, in the usual temperature, tends nearly equally to unitewith hydrogen and with charcoal, has a much stronger[Pg 124] affinity withcharcoal when at the red heat[24], and then unites with it to formcarbonic acid.
Although we are far from being able to appreciate all these powers ofaffinity, or to express their proportional energy by numbers, we arecertain, that, however variable they may be when considered in relationto the quantity of caloric with which they are combined, they are allnearly in equilibrium in the usual temperature of the atmosphere; hencevegetables neither contain oil[25], water, nor carbonic acid, tho' theycontain all the elements of these substances. The hydrogen is neithercombined with the oxygen nor with the charcoal, and reciprocally; theparticles of these three substances form a triple combination, whichremains in equilibrium[Pg 125] whilst undisturbed by caloric but a very slightincrease of temperature is sufficient to overturn this structure ofcombination.
If the increased temperature to which the vegetable is exposed does notexceed the heat of boiling water, one part of the hydrogen combines withthe oxygen, and forms water, the rest of the hydrogen combines with apart of the charcoal, and forms volatile oil, whilst the remainder ofthe charcoal, being set free from its combination with the otherelements, remains fixed in the bottom of the distilling vessel.
When, on the contrary, we employ a red heat, no water is formed, or, atleast, any that may have been produced by the first application of theheat is decomposed, the oxygen having a greater affinity with thecharcoal at this degree of heat, combines with it to form carbonic acid,and the hydrogen being left free from combination with the otherelements, unites with caloric, and escapes in the state of hydrogen gas.In this high temperature, either no oil is formed, or, if any wasproduced during the lower temperature at the beginning of theexperiment, it is decomposed by the action of the red heat. Thus thedecomposition of vegetable matter, under a high temperature, is producedby the action of double and triple affinities; while the charcoalattracts the oxygen,[Pg 126] on purpose to form carbonic acid, the caloricattracts the hydrogen, and converts it into hydrogen gas.
The distillation of every species of vegetable substance confirms thetruth of this theory, if we can give that name to a simple relation offacts. When sugar is submitted to distillation, so long as we onlyemploy a heat but a little below that of boiling water, it only losesits water of cristallization, it still remains sugar, and retains allits properties; but, immediately upon raising the heat only a littleabove that degree, it becomes blackened, a part of the charcoalseparates from the combination, water slightly acidulated passes overaccompanied by a little oil, and the charcoal which remains in theretort is nearly a third part of the original weight of the sugar.
The operation of affinities which take place during the decomposition,by fire, of vegetables which contain azote, such as the cruciferousplants, and of those containing phosphorus, is more complicated; but, asthese substances only enter into the composition of vegetables in verysmall quantities, they only, apparently, produce slight changes upon theproducts of distillation; the phosphorus seems to combine with thecharcoal, and, acquiring fixity from that union, remains behind in theretort, while the[Pg 127] azote, combining with a part of the hydrogen, formsammoniac, or volatile alkali.
Animal substances, being composed nearly of the same elements withcruciferous plants, give the same products in distillation, with thisdifference, that, as they contain a greater quantity of hydrogen andazote, they produce more oil and more ammoniac. I shall only produce onefact as a proof of the exactness with which this theory explains all thephenomena which occur during the distillation of animal substances,which is the rectification and total decomposition of volatile animaloil, commonly known by the name of Dippel's oil. When these oils areprocured by a first distillation in a naked fire they are brown, fromcontaining a little charcoal almost in a free state; but they becomequite colourless by rectification. Even in this state the charcoal intheir composition has so slight a connection with the other elements asto separate by mere exposure to the air. If we put a quantity of thisanimal oil, well rectified, and consequently clear, limpid, andtransparent, into a bell-glass filled with oxygen gas over mercury, in ashort time the gas is much diminished, being absorbed by the oil, theoxygen combining with the hydrogen of the oil forms water, which sinksto the bottom, at the same time the charcoal which was combined with thehydrogen being set free, manifests itself[Pg 128] by rendering the oil black.Hence the only way of preserving these oils colourless and transparent,is by keeping them in bottles perfectly full and accurately corked, tohinder the contact of air, which always discolours them.
Successive rectifications of this oil furnish another phenomenonconfirming our theory. In each distillation a small quantity of charcoalremains in the retort, and a little water is formed by the union of theoxygen contained in the air of the distilling vessels with the hydrogenof the oil. As this takes place in each successive distillation, if wemake use of large vessels and a considerable degree of heat, we at lastdecompose the whole of the oil, and change it entirely into water andcharcoal. When we use small vessels, and especially when we employ aslow fire, or degree of heat little above that of boiling water, thetotal decomposition of these oils, by repeated distillation, is greatlymore tedious, and more difficultly accomplished. I shall give aparticular detail to the Academy, in a separate memoir, of all myexperiments upon the decomposition of oil; but what I have related abovemay suffice to give just ideas of the composition of animal andvegetable substances, and of their decomposition by the action of fire.
[24] Though this term, red heat, does not indicate anyabsolutely determinate degree of temperature, I shall use it sometimesto express a temperature considerably above that of boiling water.—A.
[25] I must be understood here to speak of vegetables reducedto a perfectly dry state; and, with respect to oil, I do not mean thatwhich is procured by expression either in the cold, or in a temperaturenot exceeding that of boiling water; I only allude to the empyreumaticoil procured by distillation with a naked fire, in a heat superior tothe temperature of boiling water; which is the only oil declared to beproduced by the operation of fire. What I have published upon thissubject in the Memoirs of the Academy for 1786 may be consulted.—A.
The manner in which wine, cyder, mead, and all the liquors formed by thespiritous fermentation, are produced, is well known to every one. Thejuice of grapes or of apples being expressed, and the latter beingdiluted with water, they are put into large vats, which are kept in atemperature of at least 10° (54.5°) of the thermometer. A rapidintestine motion, or fermentation, very soon takes place, numerousglobules of gas form in the liquid and burst at the surface; when thefermentation is at its height, the quantity of gas disengaged is sogreat as to make the liquor appear as if boiling violently over a fire.When this gas is carefully gathered, it is found to be carbonic acidperfectly pure, and free from admixture with any other species of air orgas whatever.
When the fermentation is completed, the juice of grapes is changed frombeing sweet, and full of sugar, into a vinous liquor which no longercontains any sugar, and from which we procure, by distillation, aninflammable liquor,[Pg 130] known in commerce under the name of Spirit of Wine.As this liquor is produced by the fermentation of any saccharine matterwhatever diluted with water, it must have been contrary to theprinciples of our nomenclature to call it spirit of wine rather thanspirit of cyder, or of fermented sugar; wherefore, we have adopted amore general term, and the Arabic wordalkohol seems extremely properfor the purpose.
This operation is one of the most extraordinary in chemistry: We mustexamine whence proceed the disengaged carbonic acid and the inflammableliquor produced, and in what manner a sweet vegetable oxyd becomes thusconverted into two such opposite substances, whereof one is combustible,and the other eminently the contrary. To solve these two questions, itis necessary to be previously acquainted with the analysis of thefermentable substance, and of the products of the fermentation. We maylay it down as an incontestible axiom, that, in all the operations ofart and nature, nothing is created; an equal quantity of matter existsboth before and after the experiment; the quality and quantity of theelements remain precisely the same; and nothing takes place beyondchanges and modifications in the combination of these elements. Uponthis principle the whole art of performing chemical experiments[Pg 131]depends: We must always suppose an exact equality between the elementsof the body examined and those of the products of its analysis.
Hence, since from must of grapes we procure alkohol and carbonic acid, Ihave an undoubted right to suppose that must consists of carbonic acidand alkohol. From these premises, we have two methods of ascertainingwhat passes during vinous fermentation, by determining the nature of,and the elements which compose, the fermentable substances, or byaccurately examining the produces resulting from fermentation; and it isevident that the knowledge of either of these must lead to accurateconclusions concerning the nature and composition of the other. Fromthese considerations, it became necessary accurately to determine theconstituent elements of the fermentable substances; and, for thispurpose, I did not make use of the compound juices of fruits, therigorous analysis of which is perhaps impossible, but made choice ofsugar, which is easily analysed, and the nature of which I have alreadyexplained. This substance is a true vegetable oxyd with two bases,composed of hydrogen and charcoal brought to the state of an oxyd, by acertain proportion of oxygen; and these three elements are combined insuch a way, that a very slight force is sufficient to destroy theequilibrium of their connection. By[Pg 132] a long train of experiments, madein various ways, and often repeated, I ascertained that the proportionin which these ingredients exist in sugar, are nearly eight parts ofhydrogen, 64 parts of oxygen, and 28 parts of charcoal, all by weight,forming 100 parts of sugar.
Sugar must be mixed with about four times its weight of water, to renderit susceptible of fermentation; and even then the equilibrium of itselements would remain undisturbed, without the assistance of somesubstance, to give a commencement to the fermentation. This isaccomplished by means of a little yeast from beer; and, when thefermentation is once excited, it continues of itself until completed. Ishall, in another place, give an account of the effects of yeast, andother ferments, upon fermentable substances. I have usually employed 10libs. of yeast, in the state of paste, for each 100libs. of sugar,with as much water as is four times the weight of the sugar. I shallgive the results of my experiments exactly as they were obtained,preserving even the fractions produced by calculation.[Pg 133]
| libs. | oz. | gros | grs. | ||
| Water | 400 | 0 | 0 | 0 | |
| Sugar | 100 | 0 | 0 | 0 | |
| Yeast in paste, 10libs. composed of | { Water | 7 | 3 | 6 | 44 |
| { Dry yeast | 2 | 12 | 1 | 28 | |
| —— | —— | —— | —— | ||
| Total | 510 |
| libs. | oz. | gros | grs. | ||
| 407libs, 3oz. 6gros 44grs. of water, composed of | {Hydrogen | 61 | 1 | 2 | 71.40 |
| { Oxygen | 346 | 2 | 3 | 44.60 | |
| {Hydrogen | 8 | 0 | 0 | 0 | |
| 100libs. sugar, composed of | {Oxygen | 64 | 0 | 0 | 0 |
| {Charcoal | 28 | 0 | 0 | 0 | |
| {Hydrogen | 0 | 4 | 5 | 9.30 | |
| 2libs. 12oz. 1gros 28grs. of dry yeast, composed of | {Oxygen | 1 | 10 | 2 | 28.76 |
| { Charcoal | 0 | 12 | 4 | 59 | |
| { Azote | 0 | 0 | 5 | 2.94 | |
| ——— | ——— | —— | ——— | ||
| Total weight | 510 | 0 | 0 | 0 |
| libs. | oz. | gros | grs. | |||||
| Oxygen: | ||||||||
| of the water | 340 | 0 | 0 | 0} | libs. | oz. | gros | grs. |
| of the water in the yeast | 6 | 2 | 3 | 44.60} | 411 | 12 | 6 | 1.36 |
| of the sugar | 64 | 0 | 0 | 0} | ||||
| of the dry yeast | 1 | 10 | 2 | 28.76} | ||||
| Hydrogen: | ||||||||
| of the water | 60 | 0 | 0 | 0} | ||||
| of the water in the yeast | 1 | 1 | 2 | 71.40} | 69 | 6 | 0 | 8.70 |
| of the sugar | 8 | 0 | 0 | 0} | ||||
| of the dry yeast | 0 | 4 | 5 | 9.30} | ||||
| Charcoal: | ||||||||
| of the sugar | 28 | 0 | 0 | 0} | ||||
| of the yeast | 0 | 12 | 4 | 59.00} | 28 | 12 | 4 | 59.00 |
| Azote of the yeast | - | - | - | - } | 0 | 0 | 5 | 2.94 |
| —— | ——— | ——— | ——— | |||||
| In all | 510 | 0 | 0 | 0 |
Having thus accurately determined the nature and quantity of theconstituent elements of the materials submitted to fermentation, we havenext to examine the products resulting from that process. For thispurpose, I placed the above 510libs. of fermentable liquor in aproper[26] apparatus, by means of which I could accurately determine thequantity and quality of gas disengaged during the fermentation, andcould even weigh every one of the products[Pg 135] separately, at any period ofthe process I judged proper. An hour or two after the substances aremixed together, especially if they are kept in a temperature of from 15°(65.75°) to 18° (72.5°) of the thermometer, the first marks offermentation commence; the liquor turns thick and frothy, littleglobules of air are disengaged, which rise and burst at the surface; thequantity of these globules quickly increases, and there is a rapid andabundant production of very pure carbonic acid, accompanied with a scum,which is the yeast separating from the mixture. After some days, less ormore according to the degree of heat, the intestine motion anddisengagement of gas diminish; but these do not cease entirely, nor isthe fermentation completed for a considerable time. During the process,35libs. 5oz. 4gros 19grs. of dry carbonic acid aredisengaged, which carry alongst with them 13libs. 14oz. 5grosof water. There remains in the vessel 460libs. 11oz. 6gros 53grs. of vinous liquor, slightly acidulous. This is at first muddy, butclears of itself, and deposits a portion of yeast. When we separatelyanalise all these substances, which is effected by very troublesomeprocesses, we have the results as given in the following Tables. Thisprocess, with all the subordinate calculations and analyses, will bedetailed at large in the Memoirs of the Academy.
| libs. | oz. | gros | grs. | ||
| 35libs. 5oz. 4gros 19grs. of carbonic acid, composed of | {Oxygen | 25 | 7 | 1 | 34 |
| {Charcoal | 9 | 14 | 2 | 57 | |
| 408libs. 15oz. 5gros 14grs. of water, composed of | {Oxygen | 347 | 10 | 0 | 59 |
| {Hydrogen | 61 | 5 | 4 | 27 | |
| {Oxygen, combined with hydrogen | 31 | 6 | 1 | 64 | |
| 57libs. 11oz. 1gros 58grs. of dry alkohol, composed of | {Hydrogen, combined with oxygen | 5 | 8 | 5 | 3 |
| {Hydrogen, combined with charcoal | 4 | 0 | 5 | 0 | |
| {Charcoal, combined with hydrogen | 16 | 11 | 5 | 63 | |
| 2libs. 8oz. of dry acetous acid, composed of | {Hydrogen | 0 | 2 | 4 | 0 |
| {Oxygen | 1 | 11 | 4 | 0 | |
| {Charcoal | 0 | 10 | 0 | 0 | |
| 4libs.1 oz. 4gros 3grs. of residuum of sugar, composed of | {Hydrogen | 0 | 5 | 1 | 67 |
| {Oxygen | 2 | 9 | 7 | 27 | |
| {Charcoal | 1 | 2 | 2 | 53 | |
| {Hydrogen | 0 | 2 | 2 | 41 | |
| 1lib. 6oz. 0gros 5grs. of dry yeast, composed of | {Oxygen | 0 | 13 | 1 | 14 |
| { Charcoal | 0 | 6 | 2 | 30 | |
| {Azote | 0 | 0 | 2 | 37 | |
| —— | —— | —— | —— | ||
| 510libs. | Total | 510 | 0 | 0 | 0 |
| libs. | oz. | gros | grs. | ||
| 409 libs. 10 oz. 0 gros 54 grs. of oxygen contained in the | Water | 347 | 10 | 0 | 59 |
| Carbonic acid | 25 | 7 | 1 | 34 | |
| Alkohol | 31 | 6 | 1 | 64 | |
| Acetous acid | 1 | 11 | 4 | 0 | |
| Residuum of sugar | 2 | 9 | 7 | 27 | |
| Yeast | 0 | 13 | 1 | 14 | |
| 28 libs. 12 oz. 5 gros 59 grs. of charcoal contained in the | Carbonic acid | 9 | 14 | 2 | 57 |
| Alkohol | 16 | 11 | 5 | 63 | |
| Acetous acid | 0 | 10 | 0 | 0 | |
| Residuum of sugar | 1 | 2 | 2 | 53 | |
| Yeast | 0 | 6 | 2 | 30 | |
| 71 libs. 8 oz. 6 gros 66 grs. of hydrogen contained in the | Water | 61 | 5 | 4 | 27 |
| Water of the alkohol | 5 | 8 | 5 | 3 | |
| Combined with the charcoal of the alko. | 4 | 0 | 5 | 0 | |
| Acetous acid | 0 | 2 | 4 | 0 | |
| Residuum of sugar | 0 | 5 | 1 | 67 | |
| Yeast | 0 | 2 | 2 | 41 | |
| 2 gros 37 grs. of azote in the yeast | 0 | 0 | 2 | 37 | |
| —— | ——— | ——— | ——— | ——— | |
| 510libs. | Total | 510 | 0 | 0 | 0 |
In these results, I have been exact, even to grains; not that it ispossible, in experiments of this nature, to carry our accuracy so far,but as the experiments were made only with a few pounds of sugar, andas, for the sake of comparison, I reduced the results of the actualexperiments to the quintal or imaginary hundred[Pg 138] pounds, I thought itnecessary to leave the fractional parts precisely as produced bycalculation.
When we consider the results presented by these tables with attention,it is easy to discover exactly what occurs during fermentation. In thefirst place, out of the 100libs. of sugar employed, 4libs. 1oz.4gros 3grs. remain, without having suffered decomposition; sothat, in reality, we have only operated upon 95libs. 14oz. 3gros 69grs. of sugar; that is to say, upon 61libs. 6oz. 45grs. of oxygen, 7libs. 10oz. 6gros 6grs. of hydrogen, and26libs. 13oz. 5gros 19grs. of charcoal. By comparing thesequantities, we find that they are fully sufficient for forming the wholeof the alkohol, carbonic acid and acetous acid produced by thefermentation. It is not, therefore, necessary to suppose that any waterhas been decomposed during the experiment, unless it be pretended thatthe oxygen and hydrogen exist in the sugar in that state. On thecontrary, I have already made it evident that hydrogen, oxygen andcharcoal, the three constituent elements of vegetables, remain in astate of equilibrium or mutual union with each other which subsists solong as this union remains undisturbed by increased temperature, or bysome new compound attraction; and that then[Pg 139] only these elementscombine, two and two together, to form water and carbonic acid.
The effects of the vinous fermentation upon sugar is thus reduced to themere separation of its elements into two portions; one part isoxygenated at the expence of the other, so as to form carbonic acid,whilst the other part, being deoxygenated in favour of the former, isconverted into the combustible substance alkohol; therefore, if it werepossible to reunite alkohol and carbonic acid together, we ought to formsugar. It is evident that the charcoal and hydrogen in the alkohol donot exist in the state of oil, they are combined with a portion ofoxygen, which renders them miscible with water; wherefore these threesubstances, oxygen, hydrogen, and charcoal, exist here likewise in aspecies of equilibrium or reciprocal combination; and in fact, when theyare made to pass through a red hot tube of glass or porcelain, thisunion or equilibrium is destroyed, the elements become combined, two andtwo, and water and carbonic acid are formed.
I had formally advanced, in my first Memoirs upon the formation ofwater, that it was decomposed in a great number of chemical experiments,and particularly during the vinous fermentation. I then supposed thatwater existed ready formed in sugar, though I am now convinced thatsugar only contains the elements[Pg 140] proper for composing it. It may bereadily conceived, that it must have cost me a good deal to abandon myfirst notions, but by several years reflection, and after a great numberof experiments and observations upon vegetable substances, I have fixedmy ideas as above.
I shall finish what I have to say upon vinous fermentation, byobserving, that it furnishes us with the means of analysing sugar andevery vegetable fermentable matter. We may consider the substancessubmitted to fermentation, and the products resulting from thatoperation, as forming an algebraic equation; and, by successivelysupposing each of the elements in this equation unknown, we cancalculate their values in succession, and thus verify our experiments bycalculation, and our calculation by experiment reciprocally. I haveoften successfully employed this method for correcting the first resultsof my experiments, and to direct me in the proper road for repeatingthem to advantage. I have explained myself at large upon this subject,in a Memoir upon vinous fermentation already presented to the Academy,and which will speedily be published.
[26] The above apparatus is described in the Third Part.—A.
The phenomena of putrefaction are caused, like those of vinousfermentation, by the operation of very complicated affinities. Theconstituent elements of the bodies submitted to this process cease tocontinue in equilibrium in the threefold combination, and formthemselves anew into binary combinations[27], or compounds, consistingof two elements only; but these are entirely different from the resultsproduced by the vinous fermentation. Instead of one part of the hydrogenremaining united with part of the water and charcoal to form alkohol, asin the vinous fermentation, the whole of the hydrogen is dissipated,during putrefaction, in the form of hydrogen gas, whilst, at the sametime, the oxygen and charcoal, uniting with caloric, escape in the formof carbonic acid gas; so that, when the whole process is finished,especially[Pg 142] if the materials have been mixed with a sufficient quantityof water, nothing remains but the earth of the vegetable mixed with asmall portion of charcoal and iron. Thus putrefaction is nothing morethan a complete analysis of vegetable substance, during which the wholeof the constituent elements is disengaged in form of gas, except theearth, which remains in the state of mould[28].
Such is the result of putrefaction when the substances submitted to itcontain only oxygen, hydrogen, charcoal and a little earth. But thiscase is rare, and these substances putrify imperfectly and withdifficulty, and require a considerable time to complete theirputrefaction. It is otherwise with substances containing azote, whichindeed exists in all animal matters, and even in a considerable numberof vegetable substances. This additional element is remarkablyfavourable to putrefaction; and for this reason animal matter is mixedwith vegetable, when the putrefaction of these is wished to be hastened.The whole art of forming composts and dunghills, for the purposes ofagriculture, consists in the proper application of this admixture.
The addition of azote to the materials of putrefaction not onlyaccelerates the process,[Pg 143] that element likewise combines with part ofthe hydrogen, and forms a new substance calledvolatile alkali orammoniac. The results obtained by analysing animal matters, bydifferent processes, leave no room for doubt with regard to theconstituent elements of ammoniac; whenever the azote has been previouslyseparated from these substances, no ammoniac is produced; and in allcases they furnish ammoniac only in proportion to the azote theycontain. This composition of ammoniac is likewise fully proved by MrBerthollet, in the Memoirs of the Academy for 1785, p. 316. where hegives a variety of analytical processes by which ammoniac is decomposed,and its two elements, azote and hydrogen, procured separately.
I already mentioned in Chap. X. that almost all combustible bodies werecapable of combining with each other; hydrogen gas possesses thisquality in an eminent degree, it dissolves charcoal, sulphur, andphosphorus, producing the compounds namedcarbonated hydrogen gas,sulphurated hydrogen gas, andphosphorated hydrogen gas. The twolatter of these gasses have a peculiarly disagreeable flavour; thesulphurated hydrogen gas has a strong resemblance to the smell of rotteneggs, and the phosphorated smells exactly like putrid fish. Ammoniac haslikewise a peculiar odour, not less penetrating, or less disagreeable,than these other gasses. From[Pg 144] the mixture of these different flavoursproceeds the fetor which accompanies the putrefaction of animalsubstances. Sometimes ammoniac predominates, which is easily perceivedby its sharpness upon the eyes; sometimes, as in feculent matters, thesulphurated gas is most prevalent; and sometimes, as in putrid herrings,the phosphorated hydrogen gas is most abundant.
I long supposed that nothing could derange or interrupt the course ofputrefaction; but Mr Fourcroy and Mr Thouret have observed some peculiarphenomena in dead bodies, buried at a certain depth, and preserved to acertain degree, from contact with air; having found the muscular fleshfrequently converted into true animal fat. This must have arisen fromthe disengagement of the azote, naturally contained in the animalsubstance, by some unknown cause, leaving only the hydrogen and charcoalremaining, which are the elements proper for producing fat or oil. Thisobservation upon the possibility of converting animal substances intofat may some time or other lead to discoveries of great importance tosociety. The faeces of animals, and other excrementitious matters, arechiefly composed of charcoal and hydrogen, and approach considerably tothe nature of oil, of which they furnish a considerable quantity bydistillation with a naked fire; but the intolerable foetor whichaccompanies all the products[Pg 145] of these substances prevents our expectingthat, at least for a long time, they can be rendered useful in any otherway than as manures.
I have only given conjectural approximations in this Chapter upon thecomposition of animal substances, which is hitherto but imperfectlyunderstood. We know that they are composed of hydrogen, charcoal, azote,phosphorus, and sulphur, all of which, in a state of quintuplecombination, are brought to the state of oxyd by a larger or smallerquantity of oxygen. We are, however, still unacquainted with theproportions in which these substances are combined, and must leave it totime to complete this part of chemical analysis, as it has already donewith several others.
[27] Binary combinations are such as consist of two simpleelements combined together. Ternary, and quaternary, consist of threeand four elements.—E.
[28] In the Third Part will be given the description of anapparatus proper for being used in experiments of this kind.—A.
The acetous fermentation is nothing more than the acidification oroxygenation of wine[29], produced in the open air by means of theabsorption of oxygen. The resulting acid is the acetous acid, commonlycalled Vinegar, which is composed of hydrogen and charcoal unitedtogether in proportions not yet ascertained, and changed into the acidstate by oxygen. As vinegar is an acid, we might conclude from analogythat it contains oxygen, but this is put beyond doubt by directexperiments: In the first place, we cannot change wine into vinegarwithout the contact of air containing oxygen; secondly, this process isaccompanied by a diminution of the volume of the air in which it iscarried on from the absorption of its oxygen; and, thirdly, wine may bechanged into vinegar by any other means of oxygenation.
Independent of the proofs which these facts furnish of the acetous acidbeing produced by the oxygenation of wine, an experiment made by MrChaptal, Professor of Chemistry at Montpellier, gives us a distinct viewof what takes place in this process. He impregnated water with about itsown bulk of carbonic acid from fermenting beer, and placed this water ina cellar in vessels communicating with the air, and in a short time thewhole was converted into acetous acid. The carbonic acid gas procuredfrom beer vats in fermentation is not perfectly pure, but contains asmall quantity of alkohol in solution, wherefore water impregnated withit contains all the materials necessary for forming the acetous acid.The alkohol furnishes hydrogen and one portion of charcoal, the carbonicacid furnishes oxygen and the rest of the charcoal, and the air of theatmosphere furnishes the rest of the oxygen necessary for changing themixture into acetous acid. From this observation it follows, thatnothing but hydrogen is wanting to convert carbonic acid into acetousacid; or more generally, that, by means of hydrogen, and according tothe degree of oxygenation, carbonic acid may be changed into all thevegetable acids; and, on the contrary, that, by depriving any of thevegetable acids of their hydrogen, they may be converted into carbonicacid.[Pg 148]
Although the principal facts relating to the acetous acid are wellknown, yet numerical exactitude is still wanting, till furnished by moreexact experiments than any hitherto performed; wherefore I shall notenlarge any farther upon the subject. It is sufficiently shown by whathas been said, that the constitution of all the vegetable acids andoxyds is exactly conformable to the formation of vinegar; but fartherexperiments are necessary to teach us the proportion of the constituentelements in all these acids and oxyds. We may easily perceive, however,that this part of chemistry, like all the rest of its divisions, makesrapid progress towards perfection, and that it is already renderedgreatly more simple than was formerly believed.
[29] The word Wine, in this chapter, is used to signify theliquor produced by the vinous fermentation, whatever vegetable substancemay have been used for obtaining it.—E.
We have just seen that all the oxyds and acids from the animal andvegetable kingdoms are formed by means of a small number of simpleelements, or at least of such as have not hitherto been susceptible ofdecomposition, by means of combination with oxygen; these are azote,sulphur, phosphorus, charcoal, hydrogen, and the muriatic radical[30].We may justly admire the simplicity of the means employed by nature tomultiply qualities and forms, whether by combining three or fouracidifiable bases in different proportions, or by altering the dose ofoxygen employed for oxydating or acidifying them. We shall find themeans no less simple and diversified, and as abundantly productive offorms and qualities, in the order of bodies we are now about to treatof.
Acidifiable substances, by combining with oxygen, and their consequentconversion into acids, acquire great susceptibility of farthercombination; they become capable of uniting with earthy and metallicbodies, by which means neutral salts are formed. Acids may therefore beconsidered as truesalifying principles, and the substances with whichthey unite to form neutral salts may be calledsalifiable bases: Thenature of the union which these two principles form with each other ismeant as the subject of the present chapter.
This view of the acids prevents me from considering them as salts,though they are possessed of many of the principal properties of salinebodies, as solubility in water, &c. I have already observed that theyare the result of a first order of combination, being composed of twosimple elements, or at least of elements which act as if they weresimple, and we may therefore rank them, to use the language of Stahl, inthe order ofmixts. The neutral salts, on the contrary, are of asecondary order of combination, being formed by the union of twomixtswith each other, and may therefore be termedcompounds. Hence I shallnot arrange the alkalies[31] or earths in the class of salts, to whichI[Pg 151] allot only such as are composed of an oxygenated substance united toa base.
I have already enlarged sufficiently upon the formation of acids in thepreceding chapter, and shall not add any thing farther upon thatsubject; but having as yet given no account of the salifiable baseswhich are capable of uniting with them to form neutral salts, I mean, inthis chapter, to give an account of the nature and origin of each ofthese bases. These are potash, soda, ammoniac, lime, magnesia, barytes,argill[32], and all the metallic bodies.
We have already shown, that, when a vegetable substance is submitted tothe action of fire in distilling vessels, its component elements,oxygen, hydrogen, and charcoal, which formed a threefold combination ina state of equilibrium, unite, two and two, in obedience to affinitieswhich act conformable to the degree of heat[Pg 152] employed. Thus, at thefirst application of the fire, whenever the heat produced exceeds thetemperature of boiling water, part of the oxygen and hydrogen unite toform water; soon after the rest of the hydrogen, and part of thecharcoal, combine into oil; and, lastly, when the fire is pushed to thered heat, the oil and water, which had been formed in the early part ofthe process, become again decomposed, the oxygen and charcoal unite toform carbonic acid, a large quantity of hydrogen gas is set free, andnothing but charcoal remains in the retort.
A great part of these phenomena occur during the combustion ofvegetables in the open air; but, in this case, the presence of the airintroduces three new substances, the oxygen and azote of the air andcaloric, of which two at least produce considerable changes in theresults of the operation. In proportion as the hydrogen of thevegetable, or that which results from the decomposition of the water, isforced out in the form of hydrogen gas by the progress of the fire, itis set on fire immediately upon getting in contact with the air, wateris again formed, and the greater part of the caloric of the two gassesbecoming free produces flame. When all the hydrogen gas is driven out,burnt, and again reduced to water, the remaining charcoal continues toburn, but without flame; it is[Pg 153] formed into carbonic acid, which carriesoff a portion of caloric sufficient to give it the gasseous form; therest of the caloric, from the oxygen of the air, being set free,produces the heat and light observed during the combustion of charcoal.The whole vegetable is thus reduced into water and carbonic acid, andnothing remains but a small portion of gray earthy matter called ashes,being the only really fixed principles which enter into the constitutionof vegetables.
The earth, or rather ashes, which seldom exceeds a twentieth part of theweight of the vegetable, contains a substance of a particular nature,known under the name of fixed vegetable alkali, or potash. To obtain it,water is poured upon the ashes, which dissolves the potash, and leavesthe ashes which are insoluble; by afterwards evaporating the water, weobtain the potash in a white concrete form: It is very fixed even in avery high degree of heat. I do not mean here to describe the art ofpreparing potash, or the method of procuring it in a state of purity,but have entered upon the above detail that I might not use any word notpreviously explained.
The potash obtained by this process is always less or more saturatedwith carbonic acid, which is easily accounted for: As the potash doesnot form, or at least is not set free, but in proportion[Pg 154] as thecharcoal of the vegetable is converted into carbonic acid by theaddition of oxygen, either from the air or the water, it follows, thateach particle of potash, at the instant of its formation, or at least ofits liberation, is in contact with a particle of carbonic acid, and, asthere is a considerable affinity between these two substances, theynaturally combine together. Although the carbonic acid has less affinitywith potash than any other acid, yet it is difficult to separate thelast portions from it. The most usual method of accomplishing this is todissolve the potash in water; to this solution add two or three timesits weight of quick-lime, then filtrate the liquor and evaporate it inclose vessels; the saline substance left by the evaporation is potashalmost entirely deprived of carbonic acid. In this state it is solublein an equal weight of water, and even attracts the moisture of the airwith great avidity; by this property it furnishes us with an excellentmeans of rendering air or gas dry by exposing them to its action. Inthis state it is soluble in alkohol, though not when combined withcarbonic acid; and Mr Berthollet employs this property as a method ofprocuring potash in the state of perfect purity.
All vegetables yield less or more of potash in consequence ofcombustion, but it is furnished in various degrees of purity bydifferent vegetables; usually, indeed, from all of them it is[Pg 155] mixedwith different salts from which it is easily separable. We can hardlyentertain a doubt that the ashes, or earth which is left by vegetablesin combustion, pre-existed in them before they were burnt, forming whatmay be called the skeleton, or osseous part of the vegetable. But it isquite otherwise with potash; this substance has never yet been procuredfrom vegetables but by means of processes or intermedia capable offurnishing oxygen and azote, such as combustion, or by means of nitricacid; so that it is not yet demonstrated that potash may not be aproduce from these operations. I have begun a series of experiments uponthis object, and hope soon to be able to give an account of theirresults.
Soda, like potash, is an alkali procured by lixiviation from the ashesof burnt plants, but only from those which grow upon the sea-side, andespecially from the herbkali, whence is derived the namealkali,given to this substance by the Arabians. It has some properties incommon with potash, and others which are entirely different: In general,these two substances have peculiar characters in their salinecombinations which are proper to each, and consequently distinguish themfrom each other; thus soda,[Pg 156] which, as obtained from marine plants, isusually entirely saturated with carbonic acid, does not attract thehumidity of the atmosphere like potash, but, on the contrary,desiccates, its cristals effloresce, and are converted into a whitepowder having all the properties of soda, which it really is, havingonly lost its water of cristallization.
Hitherto we are not better acquainted with the constituent elements ofsoda than with those of potash, being equally uncertain whether itpreviously existed ready formed in the vegetable or is a combination ofelements effected by combustion. Analogy leads us to suspect that azoteis a constituent element of all the alkalies, as is the case withammoniac; but we have only slight presumptions, unconfirmed by anydecisive experiments, respecting the composition of potash and soda.
We have, however, very accurate knowledge of the composition ofammoniac, or volatile alkali, as it is called by the old chemists. MrBerthollet, in the Memoirs of the Academy for 1784, p. 316. has provedby analysis, that 1000 parts of this substance consist of about 807parts of azote combined with 193 parts of hydrogen.[Pg 157]
Ammoniac is chiefly procurable from animal substances by distillation,during which process the azote and hydrogen necessary to its formationunite in proper proportions; it is not, however, procured pure by thisprocess, being mixed with oil and water, and mostly saturated withcarbonic acid. To separate these substances it is first combined with anacid, the muriatic for instance, and then disengaged from thatcombination by the addition of lime or potash. When ammoniac is thusproduced in its greatest degree of purity it can only exist under thegasseous form, at least in the usual temperature of the atmosphere, ithas an excessively penetrating smell, is absorbed in large quantities bywater, especially if cold and assisted by compression. Water thussaturated with ammoniac has usually been termed volatile alkaline fluor;we shall call it either simply ammoniac, or liquid ammoniac, andammoniacal gas when it exists in the aëriform state.
The composition of these four earths is totally unknown, and, until bynew discoveries their constituent elements are ascertained, we arecertainly authorised to consider them as simple bodies. Art has no sharein the production of these earths, as they are all procured readyformed[Pg 158] from nature; but, as they have all, especially the three first,great tendency to combination, they are never found pure. Lime isusually saturated with carbonic acid in the state of chalk, calcariousspars, most of the marbles, &c.; sometimes with sulphuric acid, as ingypsum and plaster stones; at other times with fluoric acid formingvitreous or fluor spars; and, lastly, it is found in the waters of thesea, and of saline springs, combined with muriatic acid. Of all thesalifiable bases it is the most universally spread through nature.
Magnesia is found in mineral waters, for the most part combined withsulphuric acid; it is likewise abundant in sea-water, united withmuriatic acid; and it exists in a great number of stones of differentkinds.
Barytes is much less common than the three preceding earths; it is foundin the mineral kingdom, combined with sulphuric acid, forming heavyspars, and sometimes, though rarely, united to carbonic acid.
Argill, or the base of alum, having less tendency to combination thanthe other earths, is often found in the state of argill, uncombined withany acid. It is chiefly procurable from clays, of which, properlyspeaking, it is the base, or chief ingredient.[Pg 159]
The metals, except gold, and sometimes silver, are rarely found in themineral kingdom in their metallic state, being usually less or moresaturated with oxygen, or combined with sulphur, arsenic, sulphuricacid, muriatic acid, carbonic acid, or phosphoric acid. Metallurgy, orthe docimastic art, teaches the means of separating them from theseforeign matters; and for this purpose we refer to such chemical books astreat upon these operations.
We are probably only acquainted as yet with a part of the metallicsubstances existing in nature, as all those which have a strongeraffinity to oxygen, than charcoal possesses, are incapable of beingreduced to the metallic state, and, consequently, being only presentedto our observation under the form of oxyds, are confounded with earths.It is extremely probable that barytes, which we have just now arrangedwith earths, is in this situation; for in many experiments it exhibitsproperties nearly approaching to those of metallic bodies. It is evenpossible that all the substances we call earths may be only metallicoxyds, irreducible by any hitherto known process.
Those metallic bodies we are at present acquainted with, and which wecan reduce to the[Pg 160] metallic or reguline state, are the followingseventeen:
I only mean to consider these as salifiable bases, without entering atall upon the consideration of their properties in the arts, and for theuses of society. In these points of view each metal would require acomplete treatise, which would lead me far beyond the bounds I haveprescribed for this work.
[30] I have not ventured to omit this element, as hereenumerated with the other principles of animal and vegetable substances,though it is not at all taken notice of in the preceding chapters asentering into the composition of these bodies.—E.
[31] Perhaps my thus rejecting the alkalies from the class ofsalts may be considered as a capital defect in the method I haveadopted, and I am ready to admit the charge; but this inconvenience iscompensated by so many advantages, that I could not think it ofsufficient consequence to make me alter my plan.—A.
[32] Called Alumine by Mr Lavoisier; but as Argill has been ina manner naturalized to the language for this substance by Mr Kirwan, Ihave ventured to use it in preference.—E.
It is necessary to remark, that earths and alkalies unite with acids toform neutral salts without the intervention of any medium, whereasmetallic substances are incapable of forming this combination withoutbeing previously less or more oxygenated; strictly speaking, therefore,metals are not soluble in acids, but only metallic oxyds. Hence, when weput a metal into an acid for solution, it is necessary, in the firstplace, that it become oxygenated, either by attracting oxygen from theacid or from the water; or, in other words, that a metal cannot bedissolved in an acid unless the oxygen, either of the acid, or of thewater mixed with it, has a stronger affinity to the metal than to thehydrogen or the acidifiable base; or, what amounts to the same thing,that no metallic solution can take place without a previousdecomposition of the water, or the acid in which it is made. Theexplanation of the principal phenomena of metallic solution dependsentirely[Pg 162] upon this simple observation, which was overlooked even by theillustrious Bergman.
The first and most striking of these is the effervescence, or, to speakless equivocally, the disengagement of gas which takes place during thesolution; in the solutions made in nitric acid this effervescence isproduced by the disengagement of nitrous gas; in solutions withsulphuric acid it is either sulphurous acid gas or hydrogen gas,according as the oxydation of the metal happens to be made at theexpence of the sulphuric acid or of the water. As both nitric acid andwater are composed of elements which, when separate, can only exist inthe gasseous form, at least in the common temperature of the atmosphere,it is evident that, whenever either of these is deprived of its oxygen,the remaining element must instantly expand and assume the state of gas;the effervescence is occasioned by this sudden conversion from theliquid to the gasseous state. The same decomposition, and consequentformation of gas, takes place when solutions of metals are made insulphuric acid: In general, especially by the humid way, metals do notattract all the oxygen it contains; they therefore reduce it, not intosulphur, but into sulphurous acid, and as this acid can only exist asgas in the usual temperature, it is disengaged, and occasionseffervescence.[Pg 163]
The second phenomenon is, that, when the metals have been previouslyoxydated, they all dissolve in acids without effervescence: This iseasily explained; because, not having now any occasion for combiningwith oxygen, they neither decompose the acid nor the water by which, inthe former case, the effervescence is occasioned.
A third phenomenon, which requires particular consideration, is, thatnone of the metals produce effervescence by solution in oxygenatedmuriatic acid. During this process the metal, in the first place,carries off the excess of oxygen from the oxygenated muriatic acid, bywhich it becomes oxydated, and reduces the acid to the state of ordinarymuriatic acid. In this case there is no production of gas, not that themuriatic acid does not tend to exist in the gasseous state in the commontemperature, which it does equally with the acids formerly mentioned,but because this acid, which otherwise would expand into gas, finds morewater combined with the oxygenated muriatic acid than is necessary toretain it in the liquid form; hence it does not disengage like thesulphurous acid, but remains, and quietly dissolves and combines withthe metallic oxyd previously formed from its superabundant oxygen.
The fourth phenomenon is, that metals are absolutely insoluble in suchacids as have their[Pg 164] bases joined to oxygen by a stronger affinity thanthese metals are capable of exerting upon that acidifying principle.Hence silver, mercury, and lead, in their metallic states, are insolublein muriatic acid, but, when previously oxydated, they become readilysoluble without effervescence.
From these phenomena it appears that oxygen is the bond of union betweenmetals and acids; and from this we are led to suppose that oxygen iscontained in all substances which have a strong affinity with acids:Hence it is very probable the four eminently salifiable earths containoxygen, and their capability of uniting with acids is produced by theintermediation of that element. What I have formerly noticed relative tothese earths is considerably strengthened by the above considerations,viz. that they may very possibly be metallic oxyds, with which oxygenhas a stronger affinity than with charcoal, and consequently notreducible by any known means.
All the acids hitherto known are enumerated in the following table, thefirst column of which contains the names of the acids according to thenew nomenclature, and in the second column are placed the bases orradicals of these acids, with observations.[Pg 165]
| Names of the Acids. | Names of the Bases, with Observations. |
| 1. Sulphurous | }Sulphur. |
| 2. Sulphuric | } |
| 3. Phosphorous | }Phosphorus. |
| 4. Phosphoric | } |
| 5. Muriatic | }Muriatic radical or base, hitherto unknown. |
| 6. Oxygenated muriatic | } |
| 7. Nitrous | } |
| 8. Nitric | }Azote. |
| 9. Oxygenated nitric | } |
| 10. Carbonic | Charcoal |
| }The bases or radicals of all these acids | |
| 11. Acetous | }seem to be formed by a combination |
| 12. Acetic | }of charcoal and hydrogen; |
| 13. Oxalic | }and the only difference seems to be |
| 14. Tartarous | }owing to the different proportions in |
| 15. Pyro-tartarous | }which these elements combine to form |
| 16. Citric | }their bases, and to the different doses |
| 17. Malic | }of oxygen in their acidification. A |
| 18. Pyro-lignous | }connected series of accurate experiments |
| 19. Pyro-mucous | }is still wanted upon this subject. |
| 20. Gallic | }Our knowledge of the bases of |
| 21. Prussic | }these acids is hitherto imperfect; we |
| 22. Benzoic | }only know that they contain hydrogen |
| 23. Succinic | }and charcoal as principal elements, |
| 24. Camphoric | }and that the prussic acid contains |
| 25. Lactic | }azote. |
| 26. Saccholactic | } |
| 27. Bombic | }The base of these and all acids |
| 28. Formic | }procured from animal substances seems |
| 29. Sebacic | }to consist of charcoal, hydrogen, |
| }phosphorous, and azote. | |
| 30. Boracic | }The bases of these two are hitherto |
| 31. Fluoric | }entirely unknown. |
| 32. Antimonic | Antimony. |
| 33. Argentic | Silver. |
| 34. Arseniac(A) | Arsenic. |
| [Pg 166] | |
| 35. Bismuthic | Bismuth. |
| 36. Cobaltic | Cobalt. |
| 37. Cupric | Copper. |
| 38. Stannic | Tin. |
| 39. Ferric | Iron. |
| 40. Manganic | Manganese. |
| 41. Mercuric(B) | Mercury. |
| 42. Molybdic | Molybdena. |
| 43. Nickolic | Nickel. |
| 44. Auric | Gold. |
| 45. Platinic | Platina. |
| 46. Plumbic | Lead. |
| 47. Tungstic | Tungstein. |
| 48. Zincic | Zinc. |
[Note A: This term swerves a little from the rule in making the name ofthis acid terminate inac instead ofic. The base and acid aredistinguished in French byarsenic andarsenique; but, having chosenthe English terminationic to translate the Frenchique, I wasobliged to use this small deviation.—E.]
[Note B: Mr Lavoisier has hydrargirique; but mercurius being used forthe base or metal, the name of the acid, as above, is equally regular,and less harsh.—E.]
In this list, which contains 48 acids, I have enumerated 17 metallicacids hitherto very imperfectly known, but upon which Mr Berthollet isabout to publish a very important work. It cannot be pretended that allthe acids which exist in nature, or rather all the acidifiable bases,are yet discovered; but, on the other hand, there are considerablegrounds for supposing that a more accurate investigation than hashitherto been attempted will diminish the number of the vegetable acids,by showing that several of these, at present considered as distinctacids, are only[Pg 167] modifications of others. All that can be done in thepresent state of our knowledge is, to give a view of chemistry as itreally is, and to establish fundamental principles, by which such bodiesas may be discovered in future may receive names, in conformity with oneuniform system.
The known salifiable bases, or substances capable of being convertedinto neutral salts by union with acids, amount to 24; viz. 3 alkalies, 4earths, and 17 metallic substances; so that, in the present state ofchemical knowledge, the whole possible number of neutral salts amountsto 1152[33]. This number is upon the supposition that the metallic acidsare capable of dissolving other metals, which is a new branch ofchemistry not hitherto investigated, upon which depends all the metalliccombinations namedvitreous. There is reason to believe that many ofthese supposable saline combinations are not capable of being formed,which must greatly reduce the real number of neutral salts producible bynature and art. Even if we suppose the real number to amount only tofive or six hundred species of possible neutral salts, it is evidentthat, were we to distinguish them, after[Pg 168] the manner of the ancients,either by the names of their first discoverers, or by terms derived fromthe substances from which they are procured, we should at last have sucha confusion of arbitrary designations, as no memory could possiblyretain. This method might be tolerable in the early ages of chemistry,or even till within these twenty years, when only about thirty speciesof salts were known; but, in the present times, when the number isaugmenting daily, when every new acid gives us 24 or 48 new salts,according as it is capable of one or two degrees of oxygenation, a newmethod is certainly necessary. The method we have adopted, drawn fromthe nomenclature of the acids, is perfectly analogical, and, followingnature in the simplicity of her operations, gives a natural and easynomenclature applicable to every possible neutral salt.
In giving names to the different acids, we express the common propertyby the generical termacid, and distinguish each species by the nameof its peculiar acidifiable base. Hence the acids formed by theoxygenation of sulphur, phosphorus, charcoal, &c. are calledsulphuricacid,phosphoric acid,carbonic acid, &c. We thought it likewiseproper to indicate the different degrees of saturation with oxygen, bydifferent terminations of the same specific names.[Pg 169] Hence we distinguishbetween sulphurous and sulphuric, and between phosphorous and phosphoricacids, &c.
By applying these principles to the nomenclature of neutral salts, wegive a common term to all the neutral salts arising from the combinationof one acid, and distinguish the species by adding the name of thesalifiable base. Thus, all the neutral salts having sulphuric acid intheir composition are namedsulphats; those formed by the phosphoricacid,phosphats, &c. The species being distinguished by the names ofthe salifiable bases gives ussulphat of potash,sulphat of soda,sulphat of ammoniac,sulphat of lime,sulphat of iron, &c. As weare acquainted with 24 salifiable bases, alkaline, earthy, and metallic,we have consequently 24 sulphats, as many phosphats, and so on throughall the acids. Sulphur is, however, susceptible of two degrees ofoxygenation, the first of which produces sulphurous, and the second,sulphuric acid; and, as the neutral salts produced by these two acids,have different properties, and are in fact different salts, it becomesnecessary to distinguish these by peculiar terminations; we havetherefore distinguished the neutral salts formed by the acids in thefirst or lesser degree of oxygenation, by changing the terminationatintoite, assulphites,phosphites[34], &c. Thus, oxygenated[Pg 170] oracidified sulphur, in its two degrees of oxygenation is capable offorming 48 neutral salts, 24 of which are sulphites, and as manysulphats; which is likewise the case with all the acids capable of twodegrees of oxygenation[35].
It were both tiresome and unnecessary to follow these denominationsthrough all the varieties of their possible application; it is enough tohave given the method of naming the various salts, which, when once wellunderstood, is easily applied to every possible combination. The name ofthe combustible and acidifiable body being once known, the names of theacid it is capable of forming, and of all the neutral combinations[Pg 171] theacid is susceptible of entering into, are most readily remembered. Suchas require a more complete illustration of the methods in which the newnomenclature is applied will, in the Second Part of this book, findTables which contain a full enumeration of all the neutral salts, and,in general, all the possible chemical combinations, so far as isconsistent with the present state of our knowledge. To these I shallsubjoin short explanations, containing the best and most simple means ofprocuring the different species of acids, and some account of thegeneral properties of the neutral salts they produce.
I shall not deny, that, to render this work more complete, it would havebeen necessary to add particular observations upon each species of salt,its solubility in water and alkohol, the proportions of acid and ofsalifiable base in its composition, the quantity of its water ofcristallization, the different degrees of saturation it is susceptibleof, and, finally, the degree of force or affinity with which the acidadheres to the base. This immense work has been already begun by MessrsBergman, Morveau, Kirwan, and other celebrated chemists, but is hithertoonly in a moderate state of advancement, even the principles upon whichit is founded are not perhaps sufficiently accurate.[Pg 172]
These numerous details would have swelled this elementary treatise tomuch too great a size; besides that, to have gathered the necessarymaterials, and to have completed all the series of experimentsrequisite, must have retarded the publication of this book for manyyears. This is a vast field for employing the zeal and abilities ofyoung chemists, whom I would advise to endeavour rather to do well thanto do much, and to ascertain, in the first place, the composition of theacids, before entering upon that of the neutral salts. Every edificewhich is intended to resist the ravages of time should be built upon asure foundation; and, in the present state of chemistry, to attemptdiscoveries by experiments, either not perfectly exact, or notsufficiently rigorous, will serve only to interrupt its progress,instead of contributing to its advancement.
[33] This number excludes all triple salts, or such as containmore than one salifiable base, all the salts whose bases are over orunder saturated with acid, and those formed by the nitro-muriaticacid.—E.
[34] As all the specific names of the acids in the newnomenclature are adjectives, they would have applied severally to thevarious salifiable bases, without the invention of other terms, withperfect distinctness. Thus,sulphurous potash, andsulphuric potash,are equally distinct assulphite of potash, andsulphat of potash;and have the advantage of being more easily retained in the memory,because more naturally arising from the acids themselves, than thearbitrary terminations adopted by Mr Lavoisier.—E.
[35] There is yet a third degree of oxygenation of acids, asthe oxygenated muriatic and oxygenated nitric acids. The termsapplicable to the neutral salts resulting from the union of these acidswith salifiable bases is supplied by the Author in the Second Part ofthis Work. These are formed by prefixing the wordoxygenated to thename of the salt produced by the second degree of oxygenation. Thus,oxygenated muriat of potash,oxygenated nitrat of soda, &c.—E.
If I had strictly followed the plan I at first laid down for the conductof this work, I would have confined myself, in the Tables andaccompanying observations which compose this Second Part, to shortdefinitions of the several known acids, and abridged accounts of theprocesses by which they are obtainable, with a mere nomenclature orenumeration of the neutral salts which result from the combination ofthese acids with the various salifiable bases. But I afterwards foundthat the addition of similar Tables of all the simple substances whichenter[Pg 174] into the composition of the acids and oxyds, together with thevarious possible combinations of these elements, would add greatly tothe utility of this work, without being any great increase to its size.These additions, which are all contained in the twelve first sections ofthis Part, and the Tables annexed to these, form a kind ofrecapitulation of the first fifteen Chapters of the First Part: The restof the Tables and Sections contain all the saline combinations.
It must be very apparent that, in this Part of the Work, I have borrowedgreatly from what has been already published by Mr de Morveau in theFirst Volume of theEncyclopedie par ordre des Matières. I couldhardly have discovered a better source of information, especially whenthe difficulty of consulting books in foreign languages is considered. Imake this general acknowledgment on purpose to save the trouble ofreferences to Mr de Morveau's work in the course of the following partof mine.[Pg 175]
Simple substances belonging to all the kingdoms of nature, which may beconsidered as the elements of bodies.
| New Names. | Correspondent old Names. |
| Light | Light. |
| Caloric | {Heat. |
| {Principle or element of heat. | |
| {Fire. Igneous fluid. | |
| {Matter of fire and of heat. | |
| Oxygen | {Dephlogisticated air. |
| {Empyreal air. | |
| {Vital air, or | |
| {Base of vital air. | |
| Azote | {Phlogisticated air or gas. |
| {Mephitis, or its base. | |
| Hydrogen | {Inflammable air or gas, |
| {or the base of inflammable air. |
| New Names. | Correspondent old names. |
| Sulphur | } |
| Phosphorous | }The same names. |
| Charcoal | } |
| Muriatic radical | } |
| Fluoric radical | }Still unknown. |
| Boracic radical | } |
| New Names. | Correspondent Old Names. | |||
| Antimony | } | { | Antimony. | |
| Arsenic | } | { | Arsenic. | |
| Bismuth | } | { | Bismuth. | |
| Cobalt | } | { | Cobalt. | |
| Copper | } | { | Copper. | |
| Gold | } | { | Gold. | |
| Iron | } | { | Iron. | |
| Lead | } Regulus of | { | Lead. | |
| Manganese | } | { | Manganese. | |
| Mercury | } | { | Mercury. | |
| Molybdena | } | { | Molybdena. | |
| Nickel | } | { | Nickel. | |
| Platina | } | { | Platina. | |
| Silver | } | { | Silver. | |
| Tin | } | { | Tin. | |
| Tungstein | } | { | Tungstein. | |
| Zinc | } | { | Zinc. |
| New Names. | Correspondent old Names. |
| Lime | {Chalk, calcareous earth. |
| {Quicklime. | |
| Magnesia | {Magnesia, base of Epsom salt. |
| {Calcined or caustic magnesia. | |
| Barytes | Barytes, or heavy earth. |
| Argill | Clay, earth of alum. |
| Silex | Siliceous or vitrifiable earth. |
The principle object of chemical experiments is to decompose naturalbodies, so as separately to examine the different substances which enterinto their composition. By consulting chemical systems, it will be foundthat this science of chemical analysis has made rapid progress in ourown times. Formerly oil and salt were considered as elements of bodies,whereas later observation and experiment have shown that all salts,instead of being simple, are composed of an acid united to a base. Thebounds of analysis have been greatly enlarged by modern discoveries[36];the acids are shown to be composed of oxygen, as an acidifying principlecommon to all, united in each to a particular base. I have proved whatMr Haffenfratz had[Pg 177] before advanced, that these radicals of the acidsare not all simple elements, many of them being, like the oilyprinciple, composed of hydrogen and charcoal. Even the bases of neutralsalts have been proved by Mr Berthollet to be compounds, as he has shownthat ammoniac is composed of azote and hydrogen.
Thus, as chemistry advances towards perfection, by dividing andsubdividing, it is impossible to say where it is to end; and thesethings we at present suppose simple may soon be found quite otherwise.All we dare venture to affirm of any substance is, that it must beconsidered as simple in the present state of our knowledge, and so faras chemical analysis has hitherto been able to show. We may even presumethat the earths must soon cease to be considered as simple bodies; theyare the only bodies of the salifiable class which have no tendency tounite with oxygen; and I am much inclined to believe that this proceedsfrom their being already saturated with that element. If so, they willfall to be considered as compounds consisting of simple substances,perhaps metallic, oxydated to a certain degree. This is only hazarded asa conjecture; and I trust the reader will take care not to confound whatI have related as truths, fixed on the firm basis of observation andexperiment, with mere hypothetical conjectures.[Pg 178]
The fixed alkalies, potash, and soda, are omitted in the foregoingTable, because they are evidently compound substances, though we areignorant as yet what are the elements they are composed of.[Pg 179]
| Names of the radicals. | ||
| Oxydable or acidifiable | { Nitro-muriatic radical or | |
| base, from the mineral | { base of the acid formerly | |
| kingdom. | { called aqua regia. | |
| { Tartarous radical or base. | ||
| { Malic. | } | |
| { Citric. | } | |
| { Pyro-lignous. | } | |
| Oxydable or acidifiable | { Pyro-mucous. | } |
| hydro-carbonous or | { Pyro-tartarous. | } |
| carbono-hydrous radicals | { Oxalic. | } |
| from the vegetable | { Acetous. | } |
| kingdom. | { Succinic. | } Radicals |
| { Benzoic. | } | |
| { Camphoric. | } | |
| { Gallic. | } | |
| } | ||
| Oxydable or acidifiable | { Lactic. | } |
| radicals from the animal | { Saccholactic. | } |
| kingdom, which | { Formic. | } |
| mostly contain azote, | { Bombic. | } |
| and frequently phosphorus. | { Sebacic. | } |
| { Lithic. | } | |
| { Prussic. | } |
Note.—The radicals from the vegetable kingdom are converted by afirst degree of oxygenation into vegetable oxyds, such as sugar, starch,and gum or mucus: Those of the animal kingdom by the same means formanimal oxyds, as lymph, &c.—A.[Pg 180]
The older chemists being unacquainted with the composition of acids, andnot suspecting them to be formed by a peculiar radical or base for each,united to an acidifying principle or element common to all, could notconsequently give any name to substances of which they had not the mostdistant idea. We had therefore to invent a new nomenclature for thissubject, though we were at the same time sensible that this nomenclaturemust be susceptible of great modification when the nature of thecompound radicals shall be better understood[37].
The compound oxydable and acidifiable radicals from the vegetable andanimal kingdoms, enumerated in the foregoing table, are not hithertoreducible to systematic nomenclature, because their exact analysis is asyet unknown. We only know in general, by some experiments of my own, andsome made by Mr Hassenfratz, that most of the vegetable acids, such asthe tartarous, oxalic, citric, malic, acetous, pyro-tartarous, andpyromucous, have radicals composed of hydrogen and charcoal, combinedin[Pg 181] such a way as to form single bases, and that these acids only differfrom each other by the proportions in which these two substances enterinto the composition of their bases, and by the degree of oxygenationwhich these bases have received. We know farther, chiefly from theexperiments of Mr Berthollet, that the radicals from the animal kingdom,and even some of those from vegetables, are of a more compound nature,and, besides hydrogen and charcoal, that they often contain azote, andsometimes phosphorus; but we are not hitherto possessed of sufficientlyaccurate experiments for calculating the proportions of these severalsubstances. We are therefore forced, in the manner of the olderchemists, still to name these acids after the substances from which theyare procured. There can be little doubt that these names will be laidaside when our knowledge of these substances becomes more accurate andextensive; the termshydro-carbonous,hydro-carbonic,carbono-hydrous, andcarbono hydric[38], will then becomesubstituted for those we now employ, which will then only remain astestimonies of the imperfect state in which this part of chemistry wastransmitted to us by our predecessors.
It is evident that the oils, being composed of hydrogen and charcoalcombined, are true carbono-hydrous or hydro-carbonous radicals; and,indeed, by adding oxygen, they are convertible into vegetable oxyds andacids, according to their degrees of oxygenation. We cannot, however,affirm that oils enter in their entire state into the composition ofvegetable oxyds and acids; it is possible that they previously lose apart either of their hydrogen or charcoal, and that the remainingingredients no longer exist in the proportions necessary to constituteoils. We still require farther experiments to elucidate these points.
Properly speaking, we are only acquainted with one compound radical fromthe mineral kingdom, the nitro-muriatic, which is formed by thecombination of azote with the muriatic radical. The other compoundmineral acids have been much less attended to, from their producing lessstriking phenomena.
I have not constructed any table of the combinations of light andcaloric with the various simple and compound substances, because ourconceptions of the nature of these combinations are not hithertosufficiently accurate. We[Pg 183] know, in general, that all bodies in natureare imbued, surrounded, and penetrated in every way with caloric, whichfills up every interval left between their particles; that, in certaincases, caloric becomes fixed in bodies, so as to constitute a part evenof their solid substance, though it more frequently acts upon them witha repulsive force, from which, or from its accumulation in bodies to agreater or lesser degree, the transformation of solids into fluids, andof fluids to aëriform elasticity, is entirely owing. We have employedthe generic namegas to indicate this aëriform state of bodiesproduced by a sufficient accumulation of caloric; so that, when we wishto express the aëriform state of muriatic acid, carbonic acid, hydrogen,water, alkohol, &c. we do it by adding the wordgas to their names;thus muriatic acid gas, carbonic acid gas, hydrogen gas, aqueous gas,alkoholic gas, &c.
The combinations of light, and its mode of acting upon different bodies,is still less known. By the experiments of Mr Berthollet, it appears tohave great affinity with oxygen, is susceptible of combining with it,and contributes alongst with caloric to change it into the state of gas.Experiments upon vegetation give reason to believe that light combineswith certain parts of vegetables, and that the green of their leaves,and the various colours of their flowers, is chiefly[Pg 184] owing to thiscombination. This much is certain, that plants which grow in darknessare perfectly white, languid, and unhealthy, and that to make themrecover vigour, and to acquire their natural colours, the directinfluence of light is absolutely necessary. Somewhat similar takes placeeven upon animals: Mankind degenerate to a certain degree when employedin sedentary manufactures, or from living in crowded houses, or in thenarrow lanes of large cities; whereas they improve in their nature andconstitution in most of the country labours which are carried on in theopen air. Organization, sensation, spontaneous motion, and all theoperations of life, only exist at the surface of the earth, and inplaces exposed to the influence of light. Without it nature itself wouldbe lifeless and inanimate. By means of light, the benevolence of theDeity hath filled the surface of the earth with organization, sensation,and intelligence. The fable of Promotheus might perhaps be considered asgiving a hint of this philosophical truth, which had even presenteditself to the knowledge of the ancients. I have intentionally avoidedany disquisitions relative to organized bodies in this work, for whichreason the phenomena of respiration, sanguification, and animal heat,are not considered; but I hope, at some future time, to be able toelucidate these curious subjects.
| Combinations of oxygen with simple non-metallic substances. | Names of the simple substances. | First degree of oxygenation. | |
| New Names. | Ancient Names. | ||
| Caloric | Oxygen gas | Vital or dephlogisticated air | |
| Hydrogen. | Water(A). | ||
| Azote | Nitrous oxyd, or base of nitrous gas | Nitrous gas or air | |
| Charcoal | Oxyd of charcoal, or carbonic oxyd | Unknown | |
| Sulphur | Oxyd of sulphur | Soft sulphur | |
| Phosphorus | Oxyd of phosphorus {Residuum from the combustion of phosphorus | ||
| Muriatic radical | Muriatic oxyd | Unknown | |
| Fluoric radical | Fluoric oxyd | Unknown | |
| Boracic radical | Boracic oxyd | Unknown | |
| Combinations of oxygen with the simple metallic substances. | Antimony | Grey oxyd of antimony | Grey calx of antimony |
| Silver | Oxyd of silver | Calx of silver | |
| Arsenic | Grey oxyd of arsenic | Grey calx of arsenic | |
| Bismuth | Grey oxyd of bismuth | Grey calx of bismuth | |
| Cobalt | Grey oxyd of cobalt | Grey calx of cobalt | |
| Copper | Brown oxyd of copper | Brown calx of copper | |
| Tin | Grey oxyd of tin | Grey calx of tin | |
| Iron | Black oxyd of iron | Martial ethiops | |
| Manganese | Black oxyd of manganese | Black calx of manganese | |
| Mercury | Black oxyd of mercury | Ethiops mineral(B) | |
| Molybdena | Oxyd of molybdena | Calx of molybdena | |
| Nickel | Oxyd of nickel | Calx of nickel | |
| Gold | Yellow oxyd of gold | Yellow calx of gold | |
| Platina | Yellow oxyd of platina | Yellow calx of platina | |
| Lead | Grey oxyd of lead | Grey calx of lead | |
| Tungstein | Oxyd of Tungstein | Calx of Tungstein | |
| Zinc | Grey oxyd of zinc | Grey calx of zinc | |
| Combinations of oxygen with simple non-metallic substances. | Names of the simple substances. | Second degree of oxygenation. | |
| New Names. | Ancient Names. | ||
| Caloric | |||
| Hydrogen. | |||
| Azote | Nitrous acid | Smoaking nitrous acid | |
| Charcoal | Carbonous acid | Unknown | |
| Sulphur | Sulphurous acid | Sulphureous acid | |
| Phosphorus | Phosphorous acid | Volatile acid of phosphorus | |
| Muriatic radical | Muriatous acid | Unknown | |
| Fluoric radical | Fluorous acid | Unknown | |
| Boracic radical | Boracous acid | Unknown | |
| Combinations of oxygen with the simple metallic substances. | Antimony | White oxyd of antimony | White calx of antimony, diaphoretic antimony |
| Silver | |||
| Arsenic | White oxyd of arsenic | White calx of arsenic | |
| Bismuth | White oxyd of bismuth | White calx of bismuth | |
| Cobalt | |||
| Copper | Blue and green oxyds of copper | Blue and green calces of copper | |
| Tin | White oxyd of tin | White calx of tin, or putty of tin | |
| Iron | Yellow and red oxyds of iron | Ochre and rust of iron | |
| Manganese | White oxyd of manganese | White calx of manganese | |
| Mercury | Yellow and red oxyds of mercury | Turbith mineral, red precipitate, calcinated mercury, precipitate per se | |
| Molybdena | |||
| Nickel | |||
| Gold | Red oxyd of gold | Red calx of gold, purple precipitate of cassius | |
| Platina | |||
| Lead | Yellow and red oxyds of lead | Massicot and minium | |
| Tungstein | |||
| Zinc | White oxyd of zinc | White calx of zinc, pompholix | |
| Combinations of oxygen with simple non-metallic substances. | Names of the simple substances. | Third degree of oxygenation. | |
| New Names. | Ancient Names. | ||
| Caloric | |||
| Hydrogen. | |||
| Azote | Nitric acid | Pale, or not smoaking nitrous acid | |
| Charcoal | Carbonic acid | Fixed air | |
| Sulphur | Sulphuric acid | Vitriolic acid | |
| Phosphorus | Phosphoric acid | Phosphoric acid | |
| Muriatic radical | Muriatic acid | Marine acid | |
| Fluoric radical | Fluoric acid | Unknown till lately | |
| Boracic radical | Boracic acid | Homberg's sedative salt | |
| Combinations of oxygen with the simple metallic substances. | Antimony | Antimonic acid | |
| Silver | Argentic acid | ||
| Arsenic | Arseniac acid | Acid of arsenic | |
| Bismuth | Bismuthic acid | ||
| Cobalt | Cobaltic acid | ||
| Copper | Cupric acid | ||
| Tin | Stannic acid | ||
| Iron | Ferric acid | ||
| Manganese | Manganesic acid | ||
| Mercury | Mercuric acid | ||
| Molybdena | Molybdic acid | Acid of molybdena | |
| Nickel | Nickelic acid | ||
| Gold | Auric acid | ||
| Platina | Platinic acid | ||
| Lead | Plumbic acid | ||
| Tungstein | Tungstic acid | Acid of Tungstein | |
| Zinc | Zincic acid | ||
| Combinations of oxygen with simple non-metallic substances. | Names of the simple substances. | Fourth degree of oxygenation. | |
| New Names. | Ancient Names. | ||
| Caloric | |||
| Hydrogen. | |||
| Azote | Oxygenated nitric | Unknown acid | |
| Charcoal | Oxygenated carbonic acid | Unknown | |
| Sulphur | Oxygenated sulphuric acid | Unknown | |
| Phosphorus | Oxygenated phosphoric acid | Unknown | |
| Muriatic radical | Oxygenated muriatic acid | Dephlogisticated marine acid | |
| Fluoric radical | |||
| Boracic radical | |||
| Combinations of oxygen with the simple metallic substances. | Antimony | ||
| Silver | |||
| Arsenic | Oxygenated arseniac acid | Unknown | |
| Bismuth | |||
| Cobalt | |||
| Copper | |||
| Tin | |||
| Iron | |||
| Manganese | |||
| Mercury | |||
| Molybdena | Oxygenated molybdic acid | Unknown | |
| Nickel | |||
| Gold | |||
| Platina | |||
| Lead | |||
| Tungstein | Oxygenated Tungstic acid | Unknown | |
| Zinc | |||
[Note A: Only one degree of oxygenation of hydrogen is hithertoknown.—A.]
[Note B: Ethiops mineral is the sulphuret of mercury; this should havebeen called black precipitate of mercury.—E.][Pg 185]
Oxygen forms almost a third of the mass of our atmosphere, and isconsequently one of the most plentiful substances in nature. All theanimals and vegetables live and grow in this immense magazine of oxygengas, and from it we procure the greatest part of what we employ inexperiments. So great is the reciprocal affinity between this elementand other substances, that we cannot procure it disengaged from allcombination. In the atmosphere it is united with caloric, in the stateof oxygen gas, and this again is mixed with about two thirds of itsweight of azotic gas.
Several conditions are requisite to enable a body to become oxygenated,or to permit oxygen to enter into combination with it. In the firstplace, it is necessary that the particles of the body to be oxygenatedshall have less reciprocal attraction with each other than they have forthe oxygen, which otherwise cannot possibly combine with them. Nature,in this case, may be assisted by art, as we have it in our power todiminish the attraction of the particles of bodies almost at will byheating them, or, in other words, by introducing caloric into theinterstices[Pg 186] between their particles; and, as the attraction of theseparticles for each other is diminished in the inverse ratio of theirdistance, it is evident that there must be a certain point of distanceof particles when the affinity they possess with each other becomes lessthan that they have for oxygen, and at which oxygenation mustnecessarily take place if oxygen be present.
We can readily conceive that the degree of heat at which this phenomenonbegins must be different in different bodies. Hence, on purpose tooxygenate most bodies, especially the greater part of the simplesubstances, it is only necessary to expose them to the influence of theair of the atmosphere in a convenient degree of temperature. Withrespect to lead, mercury, and tin, this needs be but little higher thanthe medium temperature of the earth; but it requires a more considerabledegree of heat to oxygenate iron, copper, &c. by the dry way, or whenthis operation is not assisted by moisture. Sometimes oxygenation takesplace with great rapidity, and is accompanied by great sensible heat,light, and flame; such is the combustion of phosphorus in atmosphericair, and of iron in oxygen gas. That of sulphur is less rapid; and theoxygenation of lead, tin, and most of the metals, takes place vastlyslower, and consequently the disengagement of caloric, and moreespecially of light, is hardly sensible.[Pg 187]
Some substances have so strong an affinity with oxygen, and combine withit in such low degrees of temperature, that we cannot procure them intheir unoxygenated state; such is the muriatic acid, which has nothitherto been decomposed by art, perhaps even not by nature, and whichconsequently has only been found in the state of acid. It is probablethat many other substances of the mineral kingdom are necessarilyoxygenated in the common temperature of the atmosphere, and that beingalready saturated with oxygen, prevents their farther action upon thatelement.
There are other means of oxygenating simple substances besides exposureto air in a certain degree of temperature, such as by placing them incontact with metals combined with oxygen, and which have little affinitywith that element. The red oxyd of mercury is one of the best substancesfor this purpose, especially with bodies which do not combine with thatmetal. In this oxyd the oxygen is united with very little force to themetal, and can be driven out by a degree of heat only sufficient to makeglass red hot; wherefore such bodies as are capable of uniting withoxygen are readily oxygenated, by means of being mixed with red oxyd ofmercury, and moderately heated. The same effect may be, to a certaindegree, produced by means of the black oxyd of manganese, the red oxydof lead,[Pg 188] the oxyds of silver, and by most of the metallic oxyds, if weonly take care to choose such as have less affinity with oxygen than thebodies they are meant to oxygenate. All the metallic reductions andrevivifications belong to this class of operations, being nothing morethan oxygenations of charcoal, by means of the several metallic oxyds.The charcoal combines with the oxygen and with caloric, and escapes inform of carbonic acid gas, while the metal remains pure and revivified,or deprived of the oxygen which before combined with it in the form ofoxyd.
All combustible substances may likewise be oxygenated by means of mixingthem with nitrat of potash or of soda, or with oxygenated muriat ofpotash, and subjecting the mixture to a certain degree of heat; theoxygen, in this case, quits the nitrat or the muriat, and combines withthe combustible body. This species of oxygenation requires to beperformed with extreme caution, and only with very small quantities;because, as the oxygen enters into the composition of nitrats, and moreespecially of oxygenated muriats, combined with almost as much caloricas is necessary for converting it into oxygen gas, this immense quantityof caloric becomes suddenly free the instant of the combination of theoxygen with the combustible[Pg 189] body, and produces such violent explosionsas are perfectly irresistible.
By the humid way we can oxygenate most combustible bodies, and convertmost of the oxyds of the three kingdoms of nature into acids. For thispurpose we chiefly employ the nitric acid, which has a very slight holdof oxygen, and quits it readily to a great number of bodies by theassistance of a gentle heat. The oxygenated muriatic acid may be usedfor several operations of this kind, but not in them all.
I give the name ofbinary to the combinations of oxygen with thesimple substances, because in these only two elements are combined. Whenthree substances are united in one combination I call itternary, andquaternary when the combination consists of four substances united.[Pg 190]
| Names of the radicals. | Names of the resulting acids. | |
| New nomenclature. | Old nomenclature. | |
| Nitro muriatic radical | Nitro muriatic acid | Aqua regia. |
| (A) | ||
| Tartaric | Tartarous acid | Unknown till lately. |
| Malic | Malic acid | Ditto. |
| Citric | Citric acid | Acid of lemons. |
| Pyro-lignous | Pyro-lignous acid | Empyreumatic acid of wood. |
| Pyro-mucous | Pyro-mucous acid | Empyr. acid of sugar. |
| Pyro-tartarous | Pyro-tartarous acid | Empyr. acid of tartar. |
| Oxalic | Oxalic acid | Acid of sorel. |
| Acetic | {Acetous acid | Vinegar, or acid of vinegar. |
| {Acetic acid | Radical vinegar. | |
| Succinic | Succinic acid | Volatile salt of amber. |
| Benzoic | Benzotic acid | Flowers of benzoin. |
| Camphoric | Camphoric acid | Unknown till lately. |
| Gallic | Gallic acid | The astringent principle of vegetables. |
| (B) | ||
| Lactic | Lactic acid | Acid of sour whey. |
| Saccholactic | Saccholactic acid | Unknown till lately. |
| Formic | Formic acid | Acid of ants. |
| Bombic | Bombic acid | Unknown till lately. |
| Sebacic | Sebacic acid | Ditto. |
| Lithic | Lithic acid | Urinary calculus. |
| Prussic | Prussic acid | Colouring matter of Prussian blue. |
[Note A: These radicals by a first degree of oxygenation form vegetableoxyds, as sugar, starch, mucus, &c.—A.]
[Note B: These radicals by a first degree of oxygenation form the animaloxyds, as lymph, red part of the blood, animal secretions, &c.—A.][Pg 191]
I published a new theory of the nature and formation of acids in theMemoirs of the Academy for 1776, p. 671. and 1778, p. 535. in which Iconcluded, that the number of acids must be greatly larger than was tillthen supposed. Since that time, a new field of inquiry has been openedto chemists; and, instead of five or six acids which were then known,near thirty new acids have been discovered, by which means the number ofknown neutral salts have been increased in the same proportion. Thenature of the acidifiable bases, or radicals of the acids, and thedegrees of oxygenation they are susceptible of, still remain to beinquired into. I have already shown, that almost all the oxydable andacidifiable radicals from the mineral kingdom are simple, and that, onthe contrary, there hardly exists any radical in the vegetable, and moreespecially in the animal kingdom, but is composed of at least twosubstances, hydrogen and charcoal, and that azote and phosphorus arefrequently united to these, by which we have compound radicals of two,three, and four bases or simple elements united.[Pg 192]
From these observations, it appears that the vegetable and animal oxydsand acids may differ from each other in three several ways: 1st,According to the number of simple acidifiable elements of which theirradicals are composed: 2dly, According to the proportions in which theseare combined together: And, 3dly, According to their different degreesof oxygenation: Which circumstances are more than sufficient to explainthe great variety which nature produces in these substances. It is notat all surprising, after this, that most of the vegetable acids areconvertible into each other, nothing more being requisite than to changethe proportions of the hydrogen and charcoal in their composition, andto oxygenate them in a greater or lesser degree. This has been done byMr Crell in some very ingenious experiments, which have been verifiedand extended by Mr Hassenfratz. From these it appears, that charcoal andhydrogen, by a first oxygenation, produce tartarous acid, oxalic acid bya second degree, and acetous or acetic acid by a third, or higheroxygenation; only, that charcoal seems to exist in a rather smallerproportion in the acetous and acetic acids. The citric and malic acidsdiffer little from the preceding acids.
Ought we then to conclude that the oils are the radicals of thevegetable and animal acids? I have already expressed my doubts uponthis[Pg 193] subject: 1st, Although the oils appear to be formed of nothing buthydrogen and charcoal, we do not know if these are in the preciseproportion necessary for constituting the radicals of the acids: 2dly,Since oxygen enters into the composition of these acids equally withhydrogen and charcoal, there is no more reason for supposing them to becomposed of oil rather than of water or of carbonic acid. It is truethat they contain the materials necessary for all these combinations,but then these do not take place in the common temperature of theatmosphere; all the three elements remain combined in a state ofequilibrium, which is readily destroyed by a temperature only a littleabove that of boiling water[39].
| Simple Substances. | Results of the Combinations. | |
| New Nomenclature. | Old Nomenclature. | |
| Caloric | Azotic gas | Phlogisticated air, or Mephitis. |
| Hydrogen | Ammoniac | Volatile alkali. |
| {Nitrous oxyd | Base of Nitrous gas. | |
| {Nitrous acid | Smoaking nitrous acid. | |
| Oxygen | {Nitric acid | Pale nitrous acid. |
| {Oxygenated nitric acid | Unknown. | |
| {This combination is hitherto unknown; should it | ||
| {ever be discovered, it will be called, according to | ||
| Charcoal | {the principles of our nomenclature, Azuret of | |
| {Charcoal. Charcoal dissolves in azotic gas, and | ||
| {forms carbonated azotic gas. | ||
| Phosphorus. | Azuret of phosphorus. | Still unknown. |
| {Azuret of sulphur. | Still unknown. We know | |
| Sulphur | {that sulphur dissolves in azotic gas, forming | |
| {sulphurated azotic gas. | ||
| {Azote combines with charcoal and hydrogen, and | ||
| Compound | {sometimes with phosphorus, in the compound | |
| radicals | {oxydable and acidifiable bases, and is generally | |
| {contained in the radicals of the animal acids. | ||
| {Such combinations are hitherto unknown; if ever | ||
| Metallic | {discovered, they will form metallic azurets, as | |
| substances | {azuret of gold, of silver, &c. | |
| Lime | { | |
| Magnesia | { | |
| Barytes | {Entirely unknown. If ever discovered, they will | |
| Argill | {form azuret of lime, azuret of magnesia, &c. | |
| Potash | { | |
| Soda | { | |
Azote is one of the most abundant elements; combined with caloric itforms azotic gas, or mephitis, which composes nearly two thirds of theatmosphere. This element is always in the state of gas in the ordinarypressure and temperature, and no degree of compression or of cold hasbeen hitherto capable of reducing it either to a solid or liquid form.This is likewise one of the essential constituent elements of animalbodies, in which it is combined with charcoal and hydrogen, andsometimes with phosphorus; these are united together by a certainportion of oxygen, by which they are formed into oxyds or acidsaccording to the degree of oxygenation. Hence the animal substances maybe varied, in the same way with vegetables, in three different manners:1st, According to the number of elements which enter into thecomposition of the base or radical: 2dly, According to the proportionsof these elements: 3dly, According to the degree of oxygenation.
When combined with oxygen, azote forms the nitrous and nitric oxyds andacids; when with hydrogen, ammoniac is produced. Its combinations withthe other simple elements[Pg 196] are very little known; to these we give thename of Azurets, preserving the termination inuret for allnonoxygenated compounds. It is extremely probable that all the alkalinesubstances may hereafter be found to belong to this genus of azurets.
The azotic gas may be procured from atmospheric air, by absorbing theoxygen gas which is mixed with it by means of a solution of sulphuret ofpotash, or sulphuret of lime. It requires twelve or fifteen days tocomplete this process, during which time the surface in contact must befrequently renewed by agitation, and by breaking the pellicle whichforms on the top of the solution. It may likewise be procured bydissolving animal substances in dilute nitric acid very little heated.In this operation, the azote is disengaged in form of gas, which wereceive under bell glasses filled with water in the pneumato-chemicalapparatus. We may procure this gas by deflagrating nitre with charcoal,or any other combustible substance; when with charcoal, the azotic gasis mixed with carbonic acid gas, which may be absorbed by a solution ofcaustic alkali, or by lime water, after which the azotic gas remainspure. We can procure it in a fourth manner from combinations of ammoniacwith metallic oxyds, as pointed out by Mr de Fourcroy: The hydrogen ofthe ammoniac combines with the oxygen of the[Pg 197] oxyd, and forms water,whilst the azote being left free escapes in form of gas.
The combinations of azote were but lately discovered: Mr Cavendish firstobserved it in nitrous gas and acid, and Mr Berthollet in ammoniac andthe prussic acid. As no evidence of its decomposition has hithertoappeared, we are fully entitled to consider azote as a simple elementarysubstance.[Pg 198]
| Simple Substances. | Resulting Compounds. | |
| New Nomenclature. | Old Names. | |
| Caloric | Hydrogen gas | Inflammable air. |
| Azote | Ammoniac | Volatile Alkali. |
| Oxygen | Water | Water. |
| Sulphur | {Hydruret of sulphur, or } | |
| {sulphuret of hydrogen } | Hitherto unknown (A). | |
| Phosphorus | {Hydruret of phosphorus, or } | |
| {phosphuret of hydrogen } | ||
| Charcoal | {Hydro-carbonous, or } | Not known till lately. |
| {carbono-hydrous radicals(B)} | ||
| Metallic | {Metallic hydrurets(C), as} | Hitherto unknown. |
| substances, as | {hydruret of iron, &c.} | |
| iron, &c. | { | } |
[Note A: These combinations take place in the state of gas, and form,respectively, sulphurated and phosphorated oxygen gas—A.]
[Note B: This combination of hydrogen with charcoal includes the fixedand volatile oils, and forms the radicals of a considerable part of thevegetable and animal oxyds and acids. When it takes place in the stateof gas it forms carbonated hydrogen gas.—A.]
[Note C: None of these combinations are known, and it is probable thatthey cannot exist, at least in the usual temperature of the atmosphere,owing to the great affinity of hydrogen for caloric.—A.][Pg 199]
Hydrogen, as its name expresses, is one of the constituent elements ofwater, of which it forms fifteen hundredth parts by weight, combinedwith eighty-five hundredth parts of oxygen. This substance, theproperties and even existence of which was unknown till lately, is veryplentifully distributed in nature, and acts a very considerable part inthe processes of the animal and vegetable kingdoms. As it possesses sogreat affinity with caloric as only to exist in the state of gas, it isconsequently impossible to procure it in the concrete or liquid state,independent of combination.
To procure hydrogen, or rather hydrogen gas, we have only to subjectwater to the action of a substance with which oxygen has greateraffinity than it has to hydrogen; by this means the hydrogen is setfree, and, by uniting with caloric, assumes the form of hydrogen gas.Red hot iron is usually employed for this purpose: The iron, during theprocess, becomes oxydated, and is changed into a substance resemblingthe iron ore from the island of Elba. In this state of oxyd it is muchless attractible by[Pg 200] the magnet, and dissolves in acids withouteffervescence.
Charcoal, in a red heat, has the same power of decomposing water, byattracting the oxygen from its combination with hydrogen. In thisprocess carbonic acid gas is formed, and mixes with the hydrogen gas,but is easily separated by means of water or alkalies, which absorb thecarbonic acid, and leave the hydrogen gas pure. We may likewise obtainhydrogen gas by dissolving iron or zinc in dilute sulphuric acid. Thesetwo metals decompose water very slowly, and with great difficulty, whenalone, but do it with great ease and rapidity when assisted by sulphuricacid; the hydrogen unites with caloric during the process, and isdisengaged in form of hydrogen gas, while the oxygen of the water uniteswith the metal in the form of oxyd, which is immediately dissolved inthe acid, forming a sulphat of iron or of zinc.
Some very distinguished chemists consider hydrogen as thephlogistonof Stahl; and as that celebrated chemist admitted the existence ofphlogiston in sulphur, charcoal, metals, &c. they are of course obligedto suppose that hydrogen exists in all these substances, though theycannot prove their supposition; even if they could, it would not availmuch, since this disengagement of hydrogen is quite insufficient toexplain the phenomena of calcination and combustion.[Pg 201] We must alwaysrecur to the examination of this question, "Are the heat and light,which are disengaged during the different species of combustion,furnished by the burning body, or by the oxygen which combines in allthese operations?" And certainly the supposition of hydrogen beingdisengaged throws no light whatever upon this question. Besides, itbelongs to those who make suppositions to prove them; and, doubtless, adoctrine which without any supposition explains the phenomena as well,and as naturally, as theirs does by supposition, has at least theadvantage of greater simplicity[40].
| Simple Substances. | Resulting Compounds. | |
| New Nomenclature. | Old Nomenclature. | |
| Caloric | Sulphuric gas | |
| {Oxyd of sulphur | Soft sulphur. | |
| Oxygen | {Sulphurous acid | Sulphureous acid. |
| {Sulphuric acid | Vitriolic acid. | |
| Hydrogen | Sulphuret of hydrogen} | |
| Azote | azote} | Unknown Combinations. |
| Phosphorus | phosphorus} | |
| Charcoal | charcoal} | |
| Antimony | antimony | Crude antimony. |
| Silver | silver | |
| Arsenic | arsenic | Orpiment, realgar. |
| Bismuth | bismuth | |
| Cobalt | cobalt | |
| Copper | copper | Copper pyrites. |
| Tin | tin | |
| Iron | iron | Iron pyrites. |
| Manganese | manganese | |
| Mercury | mercury | Ethiops mineral, cinnabar. |
| Molybdena | molybdena | |
| Nickel | nickel | |
| Gold | gold | |
| Platina | platina | |
| Lead | lead | Galena. |
| Tungstein | tungstein | |
| Zinc | zinc | Blende. |
| Potash | potash | Alkaline liver of sulphur with fixed vegetable alkali. |
| Soda | soda | Alkaline liver of sulphur with fixed mineral alkali. |
| Ammoniac | ammoniac | Volatile liver of sulphur, smoaking liquor of Boyle. |
| Lime | lime | Calcareous liver of sulphur. |
| Magnesia | magnesia | Magnesian liver of sulphur. |
| Barytes | barytes | Barytic liver of sulphur. |
| Argill | argill | Yet unknown. |
Sulphur is a combustible substance, having a very great tendency tocombination; it is naturally in a solid state in the ordinarytemperature, and requires a heat somewhat higher than boiling water tomake it liquify. Sulphur is formed by nature in a considerable degree ofpurity in the neighbourhood of volcanos; we find it likewise, chiefly inthe state of sulphuric acid, combined with argill in aluminous schistus,with lime in gypsum, &c. From these combinations it may be procured inthe state of sulphur, by carrying off its oxygen by means of charcoal ina red heat; carbonic acid is formed, and escapes in the state of gas;the sulphur remains combined with the clay, lime, &c. in the state ofsulphuret, which is decomposed by acids; the acid unites with the earthinto a neutral salt, and the sulphur is precipitated.[Pg 204]
| Simple Substances. | Resulting Compounds. |
| Caloric | Phosphoric gas. |
| { Oxyd of phosphorus. | |
| Oxygen | { Phosphorous acid. |
| { Phosphoric acid. | |
| Hydrogen | Phosphuret of hydrogen. |
| Azote | Phosphuret of azote. |
| Sulphur | Phosphuret of Sulphur. |
| Charcoal | Phosphuret of charcoal. |
| Metallic substances | Phosphuret of metals(A). |
| Potash} | |
| Soda} | |
| Ammoniac} | Phosphuret of Potash, Soda, &c.(B) |
| Lime} | |
| Barytes} | |
| Magnesia} | |
| Argill} |
[Note A: Of all these combinations of phosphorus with metals, that withiron only is hitherto known, forming the substance formerly calledSiderite; neither is it yet ascertained whether, in this combination,the phosphorus be oxygenated or not.—A.]
[Note B: These combinations of phosphorus with the alkalies and earthsare not yet known; and, from the experiments of Mr Gengembre, theyappear to be impossible—A.][Pg 205]
Phosphorus is a simple combustible substance, which was unknown tochemists till 1667, when it was discovered by Brandt, who kept theprocess secret; soon after Kunkel found out Brandt's method ofpreparation, and made it public. It has been ever since known by thename of Kunkel's phosphorus. It was for a long time procured only fromurine; and, though Homberg gave an account of the process in the Memoirsof the Academy for 1692, all the philosophers of Europe were suppliedwith it from England. It was first made in France in 1737, before acommittee of the Academy at the Royal Garden. At present it is procuredin a more commodious and more oeconomical manner from animal bones,which are real calcareous phosphats, according to the process of MessrsGahn, Scheele, Rouelle, &c. The bones of adult animals being calcined towhiteness, are pounded, and passed through a fine silk sieve; pour uponthe fine powder a quantity of dilute sulphuric acid, less than issufficient for dissolving the whole. This acid unites with thecalcareous earth of the bones into a sulphat of lime, and the phosphoricacid remains free in the liquor. The liquid[Pg 206] is decanted off, and theresiduum washed with boiling water; this water which has been used towash out the adhering acid is joined with what was before decanted off,and the whole is gradually evaporated; the dissolved sulphat of limecristallizes in form of silky threads, which are removed, and bycontinuing the evaporation we procure the phosphoric acid under theappearance of a white pellucid glass. When this is powdered, and mixedwith one third its weight of charcoal, we procure very pure phosphorusby sublimation. The phosphoric acid, as procured by the above process,is never so pure as that obtained by oxygenating pure phosphorus eitherby combustion or by means of nitric acid; wherefore this latter shouldalways be employed in experiments of research.
Phosphorus is found in almost all animal substances, and in some plantswhich give a kind of animal analysis. In all these it is usuallycombined with charcoal, hydrogen, and azote, forming very compoundradicals, which are, for the most part, in the state of oxyds by a firstdegree of union with oxygen. The discovery of Mr Hassenfratz, ofphosphorus being contained in charcoal, gives reason to suspect that itis more common in the vegetable kingdom than has generally beensupposed: It is certain, that, by proper processes, it may be procuredfrom every individual of some of the families of plants.[Pg 207]
As no experiment has hitherto given reason to suspect that phosphorus isa compound body, I have arranged it with the simple or elementarysubstances. It takes fire at the temperature of 32° (104°) of thethermometer.
| Simple Substances. | Resulting Compounds. | |
| {Oxyd of charcoal | Unknown. | |
| Oxygen | {Carbonic acid | Fixed air, chalky acid. |
| Sulphur | Carburet of sulphur} | |
| Phosphorus | Carburet of phosphorus} | Unknown. |
| Azote | Carburet of azote} | |
| {Carbono-hydrous radical | ||
| Hydrogen | {Fixed and volatile oils | |
| {Of these only the carburets of | ||
| Metallic substances | Carburets of metals | {iron and zinc are known, and |
| {were formerly called Plumbago. | ||
| Alkalies and earths | Carburet of potash, &c. | Unknown. |
As charcoal has not been hitherto decomposed, it must, in the presentstate of our knowledge, be considered as a simple substance. By modernexperiments it appears to exist ready formed in vegetables; and I havealready remarked, that, in these, it is combined with hydrogen,sometimes with azote and phosphorus, forming compound radicals, whichmay be changed into oxyds or acids according to their degree ofoxygenation.
To obtain the charcoal contained in vegetable or animal substances, wesubject them to the action of fire, at first moderate, and afterwardsvery strong, on purpose to drive off the last portions of water, whichadhere very obstinately to the charcoal. For chemical purposes, this isusually done in retorts of stone-ware or porcellain, into which thewood, or other matter, is introduced, and then placed in a reverberatoryfurnace, raised gradually to its greatest heat: The heat volatilizes, orchanges into gas, all the parts of the body susceptible of combiningwith caloric into that form, and the charcoal, being more fixed in itsnature, remains in the retort[Pg 209] combined with a little earth and somefixed salts.
In the business of charring wood, this is done by a less expensiveprocess. The wood is disposed in heaps, and covered with earth, so as toprevent the access of any more air than is absolutely necessary forsupporting the fire, which is kept up till all the water and oil isdriven off, after which the fire is extinguished by shutting up all theair-holes.
We may analyse charcoal either by combustion in air, or rather in oxygengas, or by means of nitric acid. In either case we convert it intocarbonic acid, and sometimes a little potash and some neutral saltsremain. This analysis has hitherto been but little attended to bychemists; and we are not even certain if potash exists in charcoalbefore combustion, or whether it be formed by means of some unknowncombination during that process.
As the combinations of these substances, either with each other, or withthe other combustible bodies, are hitherto entirely unknown, we have[Pg 210]not attempted to form any table for their nomenclature. We only knowthat these radicals are susceptible of oxygenation, and of forming themuriatic, fluoric, and boracic acids, and that in the acid state theyenter into a number of combinations, to be afterwards detailed.Chemistry has hitherto been unable to disoxygenate any of them, so as toproduce them in a simple state. For this purpose, some substance must beemployed to which oxygen has a stronger affinity than to their radicals,either by means of single affinity, or by double elective attraction.All that is known relative to the origin of the radicals of these acidswill be mentioned in the sections set apart for considering theircombinations with the salifiable bases.
Before closing our account of the simple or elementary substances, itmight be supposed necessary to give a table of alloys or combinations ofmetals with each other; but, as such a table would be both exceedinglyvoluminous and very unsatisfactory, without going into a series ofexperiments not yet attempted, I have thought it adviseable to omit italtogether. All[Pg 211] that is necessary to be mentioned is, that these alloysshould be named according to the metal in largest proportion in themixture or combination; thus the termalloy of gold and silver, orgold alloyed with silver, indicates that gold is the predominatingmetal.
Metallic alloys, like all other combinations, have a point ofsaturation. It would even appear, from the experiments of Mr de laBriche, that they have two perfectly distinct degrees of saturation.[Pg 212]
| Names of the bases. | Names of the neutral salts. | |
| New nomenclature. | Notes. | |
| Barytes | Nitrite of barytes. | { |
| Potash | potash. | {These salts are only |
| Soda | soda. | {known of late, and |
| Lime | lime. | {have received no particular |
| Magnesia | magnesia. | {name in the old |
| Ammoniac | ammoniac. | {nomenclature. |
| Argill | argill. | { |
| {As metals dissolve both in nitrous and | ||
| Oxyd of zinc | zinc. | {nitric acids, metallic salts must of |
| iron | iron. | {consequence be formed having |
| manganese | manganese. | {different degrees of oxygenation. |
| cobalt | cobalt. | {Those wherein the metal is |
| nickel | nickel. | {least oxygenated must be |
| lead | lead. | {called Nitrites, when more so, |
| tin | tin. | {Nitrats; but the limits of this |
| copper | copper. | {distinction are difficultly |
| bismuth | bismuth. | {ascertainable. The older |
| antimony | antimony. | {chemists were not acquainted |
| arsenic | arsenic. | {with any of these salts. |
| mercury | mercury. | { |
| silver | {It is extremely probable that gold, silver | |
| gold | {and platina only form nitrats, and cannot subsist | |
| platina | {in the state of nitrites. | |
| Bases. | Names of the resulting neutral salts. | |||
| New nomenclature. | Old nomenclature. | |||
| Barytes | Nitrat of | barytes | Nitre, with a base of heavy earth. | |
| Potash | potash | Nitre, saltpetre. Nitre with base of potash. | ||
| Soda | soda | Quadrangular nitre. Nitre with base of mineral alkali. | ||
| Lime | lime | Calcareous nitre. Nitre with calcareous base. Mother water of nitre, or saltpetre. | ||
| Magnesia | magnesia | Magnesian nitre. Nitre with base of magnesia. | ||
| Ammoniac | ammoniac | Ammoniacal nitre. | ||
| Argill | argill | Nitrous alum. Argillaceous nitre. Nitre with base of earth of alum. | ||
| Oxyd of | zinc | zinc | Nitre of zinc. | |
| iron | iron | Nitre of iron. Martial nitre. Nitrated iron. | ||
| manganese | manganese | Nitre of manganese. | ||
| cobalt | cobalt | Nitre of cobalt. | ||
| nickel | nickel | Nitre of nickel. | ||
| lead | lead | Saturnine nitre. Nitre of lead. | ||
| tin | tin | Nitre of tin. | ||
| copper | copper | Nitre of copper or of Venus. | ||
| bismuth | bismuth | Nitre of bismuth. | ||
| antimony | antimony | Nitre of antimony. | ||
| arsenic | arsenic | Arsenical nitre. | ||
| mercury | mercury | Mercurial nitre. | ||
| silver | silver | Nitre of silver or luna. Lunar caustic. | ||
| gold | gold | Nitre of gold. | ||
| platina | platina | Nitre of platina. | ||
The nitrous and nitric acids are procured from a neutral salt long knownin the arts under the name ofsaltpetre. This salt is extracted bylixiviation from the rubbish of old buildings, from the earth ofcellars, stables, or barns, and in general of all inhabited places. Inthese earths the nitric acid is usually combined with lime and magnesia,sometimes with potash, and rarely with argill. As all these salts,excepting the nitrat of potash, attract the moisture of the air, andconsequently would be difficultly preserved, advantage is taken, in themanufactures of saltpetre and the royal refining house, of the greateraffinity of the nitric acid to potash than these other bases, by whichmeans the lime, magnesia, and argill, are precipitated, and all thesenitrats are reduced to the nitrat of potash or saltpetre[41].
The nitric acid is procured from this salt by distillation, from threeparts of pure saltpetre decomposed by one part of concentratedsulphuric[Pg 215] acid, in a retort with Woulfe's apparatus, (Pl. IV. fig. 1.)having its bottles half filled with water, and all its joints carefullyluted. The nitrous acid passes over in form of red vapours surchargedwith nitrous gas, or, in other words, not saturated with oxygen. Part ofthe acid condenses in the recipient in form of a dark orange red liquid,while the rest combines with the water in the bottles. During thedistillation, a large quantity of oxygen gas escapes, owing to thegreater affinity of oxygen to caloric, in a high temperature, than tonitrous acid, though in the usual temperature of the atmosphere thisaffinity is reversed. It is from the disengagement of oxygen that thenitric acid of the neutral salt is in this operation converted intonitrous acid. It is brought back to the state of nitric acid by heatingover a gentle fire, which drives off the superabundant nitrous gas, andleaves the nitric acid much diluted with water.
Nitric acid is procurable in a more concentrated state, and with muchless loss, by mixing very dry clay with saltpetre. This mixture is putinto an earthern retort, and distilled with a strong fire. The claycombines with the potash, for which it has great affinity, and thenitric acid passes over, slightly impregnated with nitrous gas. This iseasily disengaged by heating the acid gently in a retort, a smallquantity[Pg 216] of nitrous gas passes over into the recipient, and very pureconcentrated nitric acid remains in the retort.
We have already seen that azote is the nitric radical. If to 20-1/2parts, by weight, of azote 43-1/2 parts of oxygen be added, 64 parts ofnitrous gas are formed; and, if to this we join 36 additional parts ofoxygen, 100 parts of nitric acid result from the combination.Intermediate quantities of oxygen between these two extremes ofoxygenation produce different species of nitrous acid, or, in otherwords, nitric acid less or more impregnated with nitrous gas. Iascertained the above proportions by means of decomposition; and, thoughI cannot answer for their absolute accuracy, they cannot be far removedfrom truth. Mr Cavendish, who first showed by synthetic experiments thatazote is the base of nitric acid, gives the proportions of azote alittle larger than I have done; but, as it is not improbable that heproduced the nitrous acid and not the nitric, that circumstance explainsin some degree the difference in the results of our experiments.
As, in all experiments of a philosophical nature, the utmost possibledegree of accuracy is required, we must procure the nitric acid forexperimental purposes, from nitre which has been previously purifiedfrom all foreign matter. If, after distillation, any sulphuric acid issuspected[Pg 217] in the nitric acid, it is easily separated by dropping in alittle nitrat of barytes, so long as any precipitation takes place; thesulphuric acid, from its greater affinity, attracts the barytes, andforms with it an insoluble neutral salt, which falls to the bottom. Itmay be purified in the same manner from muriatic acid, by dropping in alittle nitrat of silver so long as any precipitation of muriat of silveris produced. When these two precipitations are finished, distill offabout seven-eighths of the acid by a gentle heat, and what comes over isin the most perfect degree of purity.
The nitric acid is one of the most prone to combination, and is at thesame time very easily decomposed. Almost all the simple substances, withthe exception of gold, silver, and platina, rob it less or more of itsoxygen; some of them even decompose it altogether. It was very ancientlyknown, and its combinations have been more studied by chemists thanthose of any other acid. These combinations were namednitres byMessrs Macquer and Beaumé; but we have changed their names to nitratsand nitrites, according as they are formed by nitric or by nitrous acid,and have added the specific name of each particular base, to distinguishthe several combinations from each other.[Pg 218]
| Names of the bases. | Resulting compounds. | |||
| New nomenclature. | Old nomenclature. | |||
| Barytes | Sulphat of | barytes | Heavy spar. Vitriol of heavy earth. | |
| Potash | potash | Vitriolated tartar. Sal de duobus. Arcanum duplicatam. | ||
| Soda | soda | Glauber's salt. | ||
| Lime | lime | Selenite, gypsum, calcareous vitriol. | ||
| Magnesia | magnesia | Epsom salt, sedlitz salt, magnesian vitriol. | ||
| Ammoniac | ammoniac | Glauber's secret sal ammoniac. | ||
| Argill | argill | Alum. | ||
| Oxyd of | zinc | zinc | White vitriol, goslar vitriol, white coperas, vitriol of zinc. | |
| iron | iron | Green coperas, green vitriol, martial vitriol, vitriol of iron. | ||
| manganese | manganese | Vitriol of manganese. | ||
| cobalt | cobalt | Vitriol of cobalt. | ||
| nickel | nickel | Vitriol of nickel. | ||
| lead | lead | Vitriol of lead. | ||
| tin | tin | Vitriol of tin. | ||
| copper | copper | Blue coperas, blue vitriol, Roman vitriol, vitriol of copper. | ||
| bismuth | bismuth | Vitriol of bismuth. | ||
| antimony | antimony | Vitriol of antimony. | ||
| arsenic | arsenic | Vitriol of arsenic. | ||
| mercury | mercury | Vitriol of mercury. | ||
| silver | silver | Vitriol of silver. | ||
| gold | gold | Vitriol of gold. | ||
| platina | platina | Vitriol of platina. | ||
For a long time this acid was procured by distillation from sulphat ofiron, in which sulphuric acid and oxyd of iron are combined, accordingto the process described by Basil Valentine in the fifteenth century;but, in modern times, it is procured more oeconomically by thecombustion of sulphur in proper vessels. Both to facilitate thecombustion, and to assist the oxygenation of the sulphur, a littlepowdered saltpetre, nitrat of potash, is mixed with it; the nitre isdecomposed, and gives out its oxygen to the sulphur, which contributesto its conversion into acid. Notwithstanding this addition, the sulphurwill only continue to burn in close vessels for a limited time; thecombination ceases, because the oxygen is exhausted, and the air of thevessels reduced almost to pure azotic gas, and because the acid itselfremains long in the state of vapour, and hinders the progress ofcombustion.
In the manufactories for making sulphuric acid in the large way, themixture of nitre and sulphur is burnt in large close built chamberslined with lead, having a little water at the bottom for facilitatingthe condensation of the vapours.[Pg 220] Afterwards, by distillation in largeretorts with a gentle heat, the water passes over, slightly impregnatedwith acid, and the sulphuric acid remains behind in a concentratedstate. It is then pellucid, without any flavour, and nearly double theweight of an equal bulk of water. This process would be greatlyfacilitated, and the combustion much prolonged, by introducing fresh airinto the chambers, by means of several pairs of bellows directed towardsthe flame of the sulphur, and by allowing the nitrous gas to escapethrough long serpentine canals, in contact with water, to absorb anysulphuric or sulphurous acid gas it might contain.
By one experiment, Mr Berthollet found that 69 parts of sulphur incombustion, united with 31 parts of oxygen, to form 100 parts ofsulphuric acid; and, by another experiment, made in a different manner,he calculates that 100 parts of sulphuric acid consists of 72 partssulphur, combined with 28 parts of oxygen, all by weight.
This acid, in common with every other, can only dissolve metals whenthey have been previously oxydated; but most of the metals are capableof decomposing a part of the acid, so as to carry off a sufficientquantity of oxygen, to render themselves soluble in the part of the acidwhich remains undecomposed. This happens with silver, mercury, iron, andzinc, in boiling[Pg 221] concentrated sulphuric acid; they become firstoxydated by decomposing part of the acid, and then dissolve in the otherpart; but they do not sufficiently disoxygenate the decomposed part ofthe acid to reconvert it into sulphur; it is only reduced to the stateof sulphurous acid, which, being volatilised by the heat, flies off inform of sulphurous acid gas.
Silver, mercury, and all the other metals except iron and zinc, areinsoluble in diluted sulphuric acid, because they have not sufficientaffinity with oxygen to draw it off from its combination either with thesulphur, the sulphurous acid, or the hydrogen; but iron and zinc, beingassisted by the action of the acid, decompose the water, and becomeoxydated at its expence, without the help of heat.[Pg 222]
| Names of the Bases. | Names of the Neutral Salts. | ||
| Barytes | Sulphite of | barytes. | |
| Potash | potash. | ||
| Soda | soda. | ||
| Lime | lime. | ||
| Magnesia | magnesia. | ||
| Ammoniac | ammoniac. | ||
| Argill | argill. | ||
| Oxyd of | zinc | zinc. | |
| iron | iron. | ||
| manganese | manganese. | ||
| cobalt | cobalt. | ||
| nickel | nickel. | ||
| lead | lead. | ||
| tin | tin. | ||
| copper | copper. | ||
| bismuth | bismuth. | ||
| antimony | antimony. | ||
| arsenic | arsenic. | ||
| mercury | mercury. | ||
| silver | silver. | ||
| gold | gold. | ||
| platina | platina. | ||
Note.—The only one of these salts known to the old chemists was thesulphite of potash, under the name ofStahl's sulphureous salt. Sothat, before our new nomenclature, these compounds must have been namedStahl's sulphureous salt, having base of fixed vegetable alkali, andso of the rest.
In this Table we have followed Bergman's order of affinity of thesulphuric acid, which is the same in regard to the earths and alkalies,but it is not certain if the order be the same for the metallicoxyds.—A.[Pg 223]
The sulphurous acid is formed by the union of oxygen with sulphur by alesser degree of oxygenation than the sulphuric acid. It is procurableeither by burning sulphur slowly, or by distilling sulphuric acid fromsilver, antimony, lead, mercury, or charcoal; by which operation a partof the oxygen quits the acid, and unites to these oxydable bases, andthe acid passes over in the sulphurous state of oxygenation. This acid,in the common pressure and temperature of the air, can only exist inform of gas; but it appears, from the experiments of Mr Clouet, that, ina very low temperature, it condenses, and becomes fluid. Water absorbs agreat deal more of this gas than of carbonic acid gas, but much lessthan it does of muriatic acid gas.
That the metals cannot be dissolved in acids without being previouslyoxydated, or by procuring oxygen, for that purpose, from the acidsduring solution, is a general and well established fact, which I haveperhaps repeated too often. Hence, as sulphurous acid is alreadydeprived of great part of the oxygen necessary for forming the sulphuricacid, it is more disposed[Pg 224] to recover oxygen, than to furnish it to thegreatest part of the metals; and, for this reason, it cannot dissolvethem, unless previously oxydated by other means. From the same principleit is that the metallic oxyds dissolve without effervescence, and withgreat facility, in sulphurous acid. This acid, like the muriatic, haseven the property of dissolving metallic oxyds surcharged with oxygen,and consequently insoluble in sulphuric acid, and in this way forms truesulphats. Hence we might be led to conclude that there are no metallicsulphites, were it not that the phenomena which accompany the solutionof iron, mercury, and some other metals, convince us that these metallicsubstances are susceptible of two degrees of oxydation, during theirsolution in acids. Hence the neutral salt in which the metal is leastoxydated must be namedsulphite, and that in which it is fullyoxydated must be calledsulphat. It is yet unknown whether thisdistinction is applicable to any of the metallic sulphats, except thoseof iron and mercury.[Pg 225]
| Names of the Bases. | Names of the Neutral Salts formed by | |
| Phosphorous Acid, | Phosphoric Acid. | |
| Phosphites of(B) | Phosphats of(C) | |
| Lime | lime | lime. |
| Barytes | barytes | barytes. |
| Magnesia | magnesia | magnesia. |
| Potash | potash | potash. |
| Soda | soda | soda. |
| Ammoniac | ammoniac | ammoniac. |
| Argill | argill | argill. |
| Oxyds of(A) | ||
| zinc | zinc | zinc. |
| iron | iron | iron. |
| manganese | manganese | manganese. |
| cobalt | cobalt | cobalt. |
| nickel | nickel | nickel. |
| lead | lead | lead. |
| tin | tin | tin. |
| copper | copper | copper. |
| bismuth | bismuth | bismuth. |
| antimony | antimony | antimony. |
| arsenic | arsenic | arsenic. |
| mercury | mercury | mercury. |
| silver | silver | silver. |
| gold | gold | gold. |
| platina | platina | platina. |
[Note A: The existence of metallic phosphites supposes that metals aresusceptible of solution in phosphoric acid at different degrees ofoxygenation, which is not yet ascertained.—A.]
[Note B: All the phosphites were unknown till lately, and consequentlyhave not hitherto received names.—A.]
[Note C: The greater part of the phosphats were only discovered of late,and have not yet been named.—A.][Pg 226]
Under the article Phosphorus, Part II. Sect. X. we have already given ahistory of the discovery of that singular substance, with someobservations upon the mode of its existence in vegetable and animalbodies. The best method of obtaining this acid in a state of purity isby burning well purified phosphorus under bell-glasses, moistened on theinside with distilled water; during combustion it absorbs twice and ahalf its weight of oxygen; so that 100 parts of phosphoric acid iscomposed of 28-1/2 parts of phosphorus united to 71-1/2 parts of oxygen.This acid may be obtained concrete, in form of white flakes, whichgreedily attract the moisture of the air, by burning phosphorus in a dryglass over mercury.
To obtain phosphorous acid, which is phosphorus less oxygenated than inthe state of phosphoric acid, the phosphorus must be burnt by a veryslow spontaneous combustion over a glass-funnel leading into a crystalphial; after a few days, the phosphorus is found oxygenated, and thephosphorous acid, in proportion as it forms, has attracted moisture fromthe air, and dropped into the phial. The phosphorous[Pg 227] acid is readilychanged into phosphoric acid by exposure for a long time to the freeair; it absorbs oxygen from the air, and becomes fully oxygenated.
As phosphorus has a sufficient affinity for oxygen to attract it fromthe nitric and muriatic acids, we may form phosphoric acid, by means ofthese acids, in a very simple and cheap manner. Fill a tubulatedreceiver, half full of concentrated nitric acid, and heat it gently,then throw in small pieces of phosphorus through the tube, these aredissolved with effervescence and red fumes of nitrous gas fly off; addphosphorus so long as it will dissolve, and then increase the fire underthe retort to drive off the last particles of nitric acid; phosphoricacid, partly fluid and partly concrete, remains in the retort.[Pg 228]
| Names of Bases | Resulting Neutral Salts. | ||
| New Nomenclature. | Old Nomenclature. | ||
| Barytes | Carbonates of | barytes(A) | Aërated or effervescent heavy earth. |
| Lime | lime | Chalk, calcareous spar, Aërated calcareous earth. | |
| Potash | potash | Effervescing or aërated fixed vegetable alkali, mephitis of potash. | |
| Soda | soda | Aërated or effervescing fixed mineral alkali, mephitic soda. | |
| Magnesia | magnesia | Aërated, effervescing, mild, or mephitic magnesia. | |
| Ammoniac | ammoniac | Aërated, effervescing, mild, or mephitic volatile alkali. | |
| Argill | argill | Aërated or effervescing argillaceous earth, or earth of alum. | |
| Oxyds of | |||
| zinc | zinc | Zinc spar, mephitic or aërated zinc. | |
| iron | iron | Sparry iron-ore, mephitic or aërated iron. | |
| manganese | manganese | Aërated manganese. | |
| cobalt | cobalt | Aërated cobalt. | |
| nickel | nickel | Aërated nickel. | |
| lead | lead | Sparry lead-ore, or aërated lead. | |
| tin | tin | Aërated tin. | |
| copper | copper | Aërated copper. | |
| bismuth | bismuth | Aërated bismuth. | |
| antimony | antimony | Aërated antimony. | |
| arsenic | arsenic | Aërated arsenic. | |
| mercury | mercury | Aërated mercury. | |
| silver | silver | Aërated silver. | |
| gold | gold | Aërated gold. | |
| platina | platina | Aërated platina. | |
[Note A: As these salts have only been understood of late, they havenot, properly speaking, any old names. Mr Morveau, in the First Volumeof the Encyclopedia, calls themMephites; Mr Bergman gives them thename ofaërated; and Mr de Fourcroy, who calls the carbonic acidchalky acid, gives them the name ofchalks.—A][Pg 229]
Of all the known acids, the carbonic is the most abundant in nature; itexists ready formed in chalk, marble, and all the calcareous stones, inwhich it is neutralized by a particular earth calledlime. Todisengage it from this combination, nothing more is requisite than toadd some sulphuric acid, or any other which has a stronger affinity forlime; a brisk effervescence ensues, which is produced by thedisengagement of the carbonic acid which assumes the state of gasimmediately upon being set free. This gas, incapable of being condensedinto the solid or liquid form by any degree of cold or of pressurehitherto known, unites to about its own bulk of water, and thereby formsa very weak acid. It may likewise be obtained in great abundance fromsaccharine matter in fermentation, but is then contaminated by a smallportion of alkohol which it holds in solution.
As charcoal is the radical of this acid, we may form it artificially, byburning charcoal in oxygen gas, or by combining charcoal and metallicoxyds in proper proportions; the oxygen of the oxyd combines with thecharcoal, forming[Pg 230] carbonic acid gas, and the metal being left free,recovers its metallic or reguline form.
We are indebted for our first knowledge of this acid to Dr Black, beforewhose time its property of remaining always in the state of gas had madeit to elude the researches of chemistry.
It would be a most valuable discovery to society, if we could decomposethis gas by any cheap process, as by that means we might obtain, foreconomical purposes, the immense store of charcoal contained incalcareous earths, marbles, limestones, &c. This cannot be effected bysingle affinity, because, to decompose the carbonic acid, it requires asubstance as combustible as charcoal itself, so that we should only makean exchange of one combustible body for another not more valuable; butit may possibly be accomplished by double affinity, since this processis so readily performed by Nature, during vegetation, from the mostcommon materials.[Pg 231]
| Names of the bases. | Resulting Neutral Salts. | |
| New nomenclature. | Old nomenclature. | |
| Barytes. | Muriat of | |
| barytes | Sea-salt, having base of heavy earth. | |
| Potash | potash | Febrifuge salt of Sylvius: Muriated vegetable fixed alkali. |
| Soda | soda | Sea-salt. |
| Lime | lime | Muriated lime. Oil of lime. |
| Magnesia | magnesia | Marine Epsom salt. Muriated magnesia. |
| Ammoniac | ammoniac | Sal ammoniac. |
| Argill | argill | {Muriated alum, sea-salt with base of earth of alum. |
| Oxyd of | ||
| zinc | zinc | Sea-salt of, or muriatic zinc. |
| iron | iron | Salt of iron, Martial sea-salt. |
| manganese | manganese | Sea-salt of manganese. |
| cobalt | cobalt | Sea-salt of cobalt. |
| nickel | nickel | Sea-salt of nickel. |
| lead | lead | Horny-lead. Plumbum corneum. |
| tin | smoaking of tin solid of tin | Smoaking liquor of Libavius. Solid butter of tin. |
| copper | copper | Sea-salt of copper. |
| bismuth | bismuth | Sea-salt of bismuth. |
| antimony | antimony | Sea-salt of antimony. |
| arsenic | arsenic | Sea-salt of arsenic. |
| mercury | {sweet of mercury | Sweet sublimate of mercury, calomel, aquila alba. |
| {corrosive of mercury | Corrosive sublimate of mercury. | |
| silver | silver | Horny silver, argentum corneum, luna cornea. |
| gold | gold | Sea-salt of gold. |
| platina | platina | Sea-salt of platina. |
| Names of the Bases. | Names of the Neutral Salts by the new Nomenclature. |
| Oxygenated muriat of | |
| Barytes | barytes. |
| Potash | potash. |
| Soda | soda. |
| Lime | lime. |
| Magnesia | magnesia. |
| Argill | argill. |
| Oxyd of | |
| zinc | zinc. |
| iron | iron. |
| manganese | manganese. |
| cobalt | cobalt. |
| nickel | nickel. |
| lead | lead. |
| tin | tin. |
| copper | copper. |
| bismuth | bismuth. |
| antimony | antimony. |
| arsenic | arsenic. |
| mercury | mercury. |
| silver | silver. |
| gold | gold. |
| platina | platina. |
This order of salts, entirely unknown to the ancient chemists, wasdiscovered in 1786 by Mr Berthollet.—A.[Pg 233]
Muriatic acid is very abundant in the mineral kingdom naturally combinedwith different salifiable bases, especially with soda, lime, andmagnesia. In sea-water, and the water of several lakes, it is combinedwith these three bases, and in mines of rock-salt it is chiefly unitedto soda. This acid does not appear to have been hitherto decomposed inany chemical experiment; so that we have no idea whatever of the natureof its radical, and only conclude, from analogy with the other acids,that it contains oxygen as its acidifying principle. Mr Bertholletsuspects the radical to be of a metallic nature; but, as Nature appearsto form this acid daily, in inhabited places, by combining miasmata withaëriform fluids, this must necessarily suppose a metallic gas to existin the atmosphere, which is certainly not impossible, but cannot beadmitted without proof.
The muriatic acid has only a moderate adherence to the salifiable bases,and can readily be driven from its combination with these by sulphuricacid. Other acids, as the nitric, for instance, may answer the samepurpose; but nitric acid being volatile, would mix, duringdistillation,[Pg 234] with the muriatic. About one part of sulphuric acid issufficient to decompose two parts of decrepitated sea-salt. Thisoperation is performed in a tubulated retort, having Woulfe's apparatus,(Pl. IV. Fig. 1.), adapted to it. When all the junctures are properlylured, the sea-salt is put into the retort through the tube, thesulphuric acid is poured on, and the opening immediately closed with itsground crystal stopper. As the muriatic acid can only subsist in thegaseous form in the ordinary temperature, we could not condense itwithout the presence of water. Hence the use of the water with which thebottles in Woulfe's apparatus are half filled; the muriatic acid gas,driven off from the sea-salt in the retort, combines with the water, andforms what the old chemists calledsmoaking spirit of salt, orGlauber's spirit of sea-salt, which we now namemuriatic acid.
The acid obtained by the above process is still capable of combiningwith a farther dose of oxygen, by being distilled from the oxyds ofmanganese, lead, or mercury, and the resulting acid, which we nameoxygenated muriatic acid, can only, like the former, exist in thegasseous form, and is absorbed, in a much smaller quantity by water.When the impregnation of water with this gas is pushed beyond a certainpoint, the superabundant acid precipitates to the bottom of the vesselsin a concrete form. Mr Berthollet has[Pg 235] shown that this acid is capableof combining with a great number of the salifiable bases; the neutralsalts which result from this union are susceptible of deflagrating withcharcoal, and many of the metallic substances; these deflagrations arevery violent and dangerous, owing to the great quantity of caloric whichthe oxygen carries alongst with it into the composition of oxygenatedmuriatic acid.[Pg 236]
| Names of the Bases. | Names of the Neutral Salts. | ||
| Argill | Nitro-muriat of | argill. | |
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| antimony | antimony. | ||
| silver | silver. | ||
| arsenic | arsenic. | ||
| Barytes | barytes. | ||
| Oxyd of | bismuth | bismuth. | |
| Lime | lime. | ||
| Oxyd of | |||
| cobalt | cobalt. | ||
| copper | copper. | ||
| tin | tin. | ||
| iron | iron. | ||
| Magnesia | magnesia. | ||
| Oxyd of | |||
| manganese | manganese. | ||
| mercury | mercury. | ||
| molybdena | molybdena. | ||
| nickel | nickel. | ||
| gold | gold. | ||
| platina | platina. | ||
| lead | lead. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Oxyd of | |||
| tungstein | tungstein. | ||
| zinc | zinc. | ||
Note.—Most of these combinations, especially those with the earthsand alkalies, have been little examined, and we are yet to learn whetherthey form a mixed salt in which the compound radical remains combined,or if the two acids separate, to form two distinct neutral salts.—A.[Pg 237]
The nitro-muriatic acid, formerly calledaqua regia, is formed by amixture of nitric and muriatic acids; the radicals of these two acidscombine together, and form a compound base, from which an acid isproduced, having properties peculiar to itself, and distinct from thoseof all other acids, especially the property of dissolving gold andplatina.
In dissolutions of metals in this acid, as in all other acids, themetals are first oxydated by attracting a part of the oxygen from thecompound radical. This occasions a disengagement of a particular speciesof gas not hitherto described, which may be callednitro-muriatic gas;it has a very disagreeable smell, and is fatal to animal life whenrespired; it attacks iron, and causes it to rust; it is absorbed inconsiderable quantity by water, which thereby acquires some slightcharacters of acidity. I had occasion to make these remarks during acourse of experiments upon platina, in which I dissolved a considerablequantity of that metal in nitro-muriatic acid.
I at first suspected that, in the mixture of nitric and muriatic acids,the latter attracted a[Pg 238] part of the oxygen from the former, and becameconverted into oxygenated muriatic acid, which gave it the property ofdissolving gold; but several facts remain inexplicable upon thissupposition. Were it so, we must be able to disengage nitrous gas byheating this acid, which however does not sensibly happen. From theseconsiderations, I am led to adopt the opinion of Mr Berthollet, and toconsider nitro-muriatic acid as a single acid, with a compound base orradical.[Pg 239]
| Names of the Bases. | Names of the Neutral Salts. | ||
| Lime | Fluat of | lime. | |
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| arsenic | arsenic. | ||
| bismuth | bismuth. | ||
| mercury | mercury. | ||
| silver | silver. | ||
| gold | gold. | ||
| platina | platina. | ||
| And by the dry way, | |||
| Argill | Fluat of | argill. | |
Note.—These combinations were entirely unknown to the old chemists,and consequently have no names in the old nomenclature.—A.[Pg 240]
Fluoric exists ready formed by Nature in the fluoric spars[42], combinedwith calcareous earth, so as to form an insoluble neutral salt. Toobtain it disengaged from that combination, fluor spar, or fluat oflime, is put into a leaden retort, with a proper quantity of sulphuricacid, a recipient likewise of lead, half full of water, is adapted, andfire is applied to the retort. The sulphuric acid, from its greateraffinity, expels the fluoric acid which passes over and is absorbed bythe water in the receiver. As fluoric acid is naturally in the gasseousform in the ordinary temperature, we can receive it in apneumato-chemical apparatus over mercury. We are obliged to employmetallic vessels in this process, because fluoric acid dissolves glassand silicious earth, and even renders these bodies volatile, carryingthem over with itself in distillation in the gasseous form.
We are indebted to Mr Margraff for our first acquaintance with thisacid, though, as he could never procure it free from combination with aconsiderable quantity of silicious earth, he was[Pg 241] ignorant of its beingan acid sui generis. The Duke de Liancourt, under the name of MrBoulanger, considerably increased our knowledge of its properties; andMr Scheele seems to have exhausted the subject. The only thing remainingis to endeavour to discover the nature of the fluoric radical, of whichwe cannot hitherto form any ideas, as the acid does not appear to havebeen decomposed in any experiment. It is only by means of compoundaffinity that experiments ought to be made with this view, with anyprobability of success.[Pg 242]
| Bases. | Neutral Salts. | ||
| Lime | Borat of | lime. | |
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| mercury | mercury. | ||
| Argill | argill. | ||
Note.—Most of these combinations were neither known nor named by theold chemists. The boracic acid was formerly calledsedative salt, andits compoundsborax, with base of fixed vegetable alkali, &c.—A.[Pg 243]
This is a concrete acid, extracted from a salt procured from Indiacalledborax ortincall. Although borax has been very long employedin the arts, we have as yet very imperfect knowledge of its origin, andof the methods by which it is extracted and purified; there is reason tobelieve it to be a native salt, found in the earth in certain parts ofthe east, and in the water of some lakes. The whole trade of borax is inthe hands of the Dutch, who have been exclusively possessed of the artof purifying it till very lately, that Messrs L'Eguillier of Paris haverivalled them in the manufacture; but the process still remains a secretto the world.
By chemical analysis we learn that borax is a neutral salt with excessof base, consisting of soda, partly saturated with a peculiar acid longcalledHomberg's sedative salt, nowthe boracic acid. This acid isfound in an uncombined state in the waters of certain lakes. That ofCherchiais in Italy contains 94-1/2 grains in each pint of water.
To obtain boracic acid, dissolve some borax in boiling water, filtratethe solution, and add sulphuric acid, or any other having greateraffinity[Pg 244] to soda than the boracic acid; this latter acid is separated,and is procured in a crystalline form by cooling. This acid was longconsidered as being formed during the process by which it is obtained,and was consequently supposed to differ according to the nature of theacid employed in separating it from the soda; but it is now universallyacknowledged that it is identically the same acid, in whatever wayprocured, provided it be properly purified from mixture of other acids,by warning, and by repeated solution and cristallization. It is solubleboth in water and alkohol, and has the property of communicating a greencolour to the flame of that spirit. This circumstance led to a suspicionof its containing copper, which is not confirmed by any decisiveexperiment. On the contrary, if it contain any of that metal, it mustonly be considered as an accidental mixture. It combines with thesalifiable bases in the humid way; and though, in this manner, it isincapable of dissolving any of the metals directly, this combination isreadily affected by compound affinity.
The Table presents its combinations in the order of affinity in thehumid way; but there is a considerable change in the order when weoperate via sicca; for, in that case, argill, though the last in ourlist, must be placed immediately after soda.[Pg 245]
The boracic radical is hitherto unknown; no experiments having as yetbeen able to decompose the acid; We conclude, from analogy with theother acids, that oxygen exists in its composition as the acidifyingprinciple.[Pg 246]
| Bases. | Neutral Salts. | ||
| Lime | Arseniat of | lime. | |
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| bismuth | bismuth. | ||
| mercury | mercury. | ||
| antimony | antimony. | ||
| silver | silver. | ||
| gold | gold. | ||
| platina | platina. | ||
| Argill | argill. | ||
Note.—This order of salts was entirely unknown to the antientchemists. Mr Macquer, in 1746, discovered the combinations of arseniacacid with potash and soda, to which he gave the name ofarsenicalneutral salts.—A.[Pg 247]
In the Collections of the Academy for 1746, Mr Macquer shows that, whena mixture of white oxyd of arsenic and nitre are subjected to the actionof a strong fire, a neutral salt is obtained, which he callsneutralsalt of arsenic. At that time, the cause of this singular phenomenon,in which a metal acts the part of an acid, was quite unknown; but moremodern experiments teach that, during this process, the arsenic becomesoxygenated, by carrying off the oxygen of the nitric acid; it is thusconverted into a real acid, and combines with the potash. There areother methods now known for oxygenating arsenic, and obtaining its acidfree from combination. The most simple and most effectual of these is asfollows: Dissolve white oxyd of arsenic in three parts, by weight, ofmuriatic acid; to this solution, in a boiling state, add two parts ofnitric acid, and evaporate to dryness. In this process the nitric acidis decomposed, its oxygen unites with the oxyd of arsenic, and convertsit into an acid, and the nitrous radical flies off in the state ofnitrous gas; whilst the muriatic acid is converted by the heat intomuriatic acid gas, and may be collected in proper vessels. The arseniacacid is entirely[Pg 248] freed from the other acids employed during the processby heating it in a crucible till it begins to grow red; what remains ispure concrete arseniac acid.
Mr Scheele's process, which was repeated with great success by MrMorveau, in the laboratory at Dijon, is as follows: Distil muriatic acidfrom the black oxyd of manganese, this converts it into oxygenatedmuriatic acid, by carrying off the oxygen from the manganese, receivethis in a recipient containing white oxyd of arsenic, covered by alittle distilled water; the arsenic decomposes the oxygenated muriaticacid, by carrying off its supersaturation of oxygen, the arsenic isconverted into arseniac acid, and the oxygenated muriatic acid isbrought back to the state of common muriatic acid. The two acids areseparated by distillation, with a gentle heat increased towards the endof the operation, the muriatic acid passes over, and the arseniac acidremains behind in a white concrete form.
The arseniac acid is considerably less volatile than white oxyd ofarsenic; it often contains white oxyd of arsenic in solution, owing toits not being sufficiently oxygenated; this is prevented by continuingto add nitrous acid, as in the former process, till no more nitrous gasis produced. From all these observations I would give the followingdefinition of[Pg 249] arseniac acid. It is a white concrete metallic acid,formed by the combination of arsenic with oxygen, fixed in a red heat,soluble in water, and capable of combining with many of the salifiablebases.
Molybdena is a particular metallic body, capable of being oxygenated, sofar as to become a true concrete acid[44]. For this purpose, one partore of molybdena, which is a natural sulphuret of that metal, is putinto a retort, with five or six parts nitric acid, diluted with aquarter of its weight of water, and heat is applied to the retort; theoxygen of the nitric acid acts both upon the molybdena and the sulphur,converting the one into molybdic, and the other into sulphuric acid;pour on fresh quantities of nitric acid so long as any red fumes ofnitrous[Pg 250] gas escape; the molydbena is then oxygenated as far as ispossible, and is found at the bottom of the retort in a pulverulentform, resembling chalk. It must be washed in warm water, to separate anyadhering particles of sulphuric acid; and, as it is hardly soluble, welose very little of it in this operation. All its combinations withsalifiable bases were unknown to the ancient chemists.
| Bases. | Neutral Salts. | |
| Lime | Tungstat of | lime. |
| Barytes | barytes. | |
| Magnesia | magnesia. | |
| Potash | potash. | |
| Soda | soda. | |
| Ammoniac | ammoniac. | |
| Argill | argill. | |
| Oxyd of antimony(A), &c. | antimony(B), &c. | |
[Note A: The combinations with metallic oxyds were set down by MrLavoisier in alphabetical order; their order of affinity being unknown,I have omitted them, as serving no purpose.—E.]
[Note B: All these salts were unknown to the ancient chemists.—A.]
Tungstein is a particular metal, the ore of which has frequently beenconfounded with that of tin. The specific gravity of this ore is towater as 6 to 1; in its form of cristallization it resembles[Pg 252] thegarnet, and varies in colour from a pearl-white to yellow and reddish;it is found in several parts of Saxony and Bohemia. The mineral calledWolfram, which is frequent in the mines of Cornwal, is likewise an oreof this metal. In all these ores the metal is oxydated; and, in some ofthem, it appears even to be oxygenated to the state of acid, beingcombined with lime into a true tungstat of lime.
To obtain the acid free, mix one part of ore of tungstein with fourparts of carbonat of potash, and melt the mixture in a crucible, thenpowder and pour on twelve parts of boiling water, add nitric acid, andthe tungstic acid precipitates in a concrete form. Afterwards, to insurethe complete oxygenation of the metal, add more nitric acid, andevaporate to dryness, repeating this operation so long as red fumes ofnitrous gas are produced. To procure tungstic acid perfectly pure, thefusion of the ore with carbonat of potash must be made in a crucible ofplatina, otherwise the earth of the common crucibles will mix with theproducts, and adulterate the acid.[Pg 253]
| Bases. | Neutral Salts. | ||
| Lime | Tartarite of | lime. | |
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Argill | argill. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| iron | iron. | ||
| manganese | manganese. | ||
| cobalt | cobalt. | ||
| nickel | nickel. | ||
| lead | lead. | ||
| tin | tin. | ||
| copper | copper. | ||
| bismuth | bismuth. | ||
| antimony | antimony. | ||
| arsenic | arsenic. | ||
| silver | silver. | ||
| mercury | mercury. | ||
| gold | gold. | ||
| platina | platina. | ||
Tartar, or the concretion which fixes to the inside of vessels in whichthe fermentation of wine is completed, is a well known salt, composed ofa peculiar acid, united in considerable excess to potash. Mr Scheelefirst pointed out the method of obtaining this acid pure. Havingobserved that it has a greater affinity to lime than to potash, hedirects us to proceed in the following manner. Dissolve purified tartarin boiling water, and add a sufficient quantity of lime till the acid becompletely saturated. The tartarite of lime which is formed, beingalmost insoluble in cold water, falls to the bottom, and is separatedfrom the solution of potash by decantation; it is afterwards washed incold water, and dried; then pour on some sulphuric acid, diluted witheight or nine parts of water, digest for twelve hours in a gentle heat,frequently stirring the mixture; the sulphuric acid combines with thelime, and the tartarous acid is left free. A small quantity of gas, nothitherto examined, is disengaged during this process. At the end oftwelve hours, having decanted off the clear liquor, wash the sulphat oflime in cold water, which add to the decanted[Pg 255] liquor, then evaporatethe whole, and the tartarous acid is obtained in a concrete form. Twopounds of purified tartar, by means of from eight to ten ounces ofsulphuric acid, yield about eleven ounces of tartarous acid.
As the combustible radical exists in excess, or as the acid from tartaris not fully saturated with oxygen, we call ittartarous acid, and theneutral salts formed by its combinations with salifiable basestartarites. The base of the tartarous acid is a carbono-hydrous orhydro-carbonous radical, less oxygenated than in the oxalic acid; and itwould appear, from the experiments of Mr Hassenfratz, that azote entersinto the composition of the tartarous radical, even in considerablequantity. By oxygenating the tartarous acid, it is convertible intooxalic, malic, and acetous acids; but it is probable the proportions ofhydrogen and charcoal in the radical are changed during theseconversions, and that the difference between these acids does not aloneconsist in the different degrees of oxygenation.
The tartarous acid is susceptible of two degrees of saturation in itscombinations with the fixed alkalies; by one of these a salt is formedwith excess of acid, improperly calledcream of tartar, which in ournew nomenclature is namedacidulous tartarite of potash; by a secondor equal degree of saturation a perfectly neutral salt is formed,formerly calledvegetable salt,[Pg 256] which we nametartarite of potash.With soda this acid forms tartarite of soda, formerly calledsal deSeignette, orsal polychrest of Rochell.
The malic acid exists ready formed in the sour juice of ripe and unripeapples, and many other fruits, and is obtained as follows: Saturate thejuice of apples with potash or soda, and add a proper proportion ofacetite of lead dissolved in water; a double decomposition takes place,the malic acid combines with the oxyd of lead and precipitates, beingalmost insoluble, and the acetite of potash or soda remains in theliquor. The malat of lead being separated by decantation, is washed withcold water, and some dilute sulphuric acid is added; this unites withthe lead into an insoluble sulphat, and the malic acid remains free inthe liquor.
This acid, which is found mixed with citric and tartarous acid in agreat number of fruits, is a kind of medium between oxalic and acetous[Pg 257]acids being more oxygenated than the former, and less so than thelatter. From this circumstance, Mr Hermbstadt calls itimperfectvinegar; but it differs likewise from acetous acid, by having rathermore charcoal, and less hydrogen, in the composition of its radical.
When an acid much diluted has been used in the foregoing process, theliquor contains oxalic as well as malic acid, and probably a littletartarous, these are separated by mixing lime-water with the acids,oxalat, tartarite, and malat of lime are produced; the two former, beinginsoluble, are precipitated, and the malat of lime remains dissolved;from this the pure malic acid is separated by the acetite of lead, andafterwards by sulphuric acid, as directed above.[Pg 258]
| Bases. | Neutral Salts. | ||
| Barytes | Citrat of | barytes. | |
| Lime | lime. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| arsenic | arsenic. | ||
| mercury | mercury. | ||
| antimony | antimony. | ||
| silver | silver. | ||
| gold | gold. | ||
| platina | platina. | ||
| Argill | argill. | ||
[Note A: These combinations were unknown to the ancient chemists. Theorder of affinity of the salifiable bases with this acid was determinedby Mr Bergman and by Mr de Breney of the Dijon Academy.—A.][Pg 259]
The citric acid is procured by expression from lemons, and is found inthe juices of many other fruits mixed with malic acid. To obtain it pureand concentrated, it is first allowed to depurate from the mucous partof the fruit by long rest in a cool cellar, and is afterwardsconcentrated by exposing it to the temperature of 4 or 5 degrees belowZero, from 21° to 23° of Fahrenheit, the water is frozen, and the acidremains liquid, reduced to about an eighth part of its original bulk. Alower degree of cold would occasion the acid to be engaged amongst theice, and render it difficultly separable. This process was pointed outby Mr Georgius.
It is more easily obtained by saturating the lemon-juice with lime, soas to form a citrat of lime, which is insoluble in water; wash thissalt, and pour on a proper quantity of sulphuric acid; this forms asulphat of lime, which precipitates and leaves the citric acid free inthe liquor.[Pg 260]
| Bases. | Neutral Salts. | ||
| Lime | Pyro-mucite of | lime. | |
| Barytes | barytes. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Magnesia | magnesia. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| arsenic | arsenic. | ||
| bismuth | bismuth. | ||
| mercury | mercury. | ||
| antimony | antimony. | ||
| silver | silver. | ||
| gold | gold. | ||
| platina | platina. | ||
| Argill | argill. | ||
[Note A: The above affinities were determined by Messrs de Morveau andEloI Boursier de Clervaux. These combinations were entirely unknown tilllately.—A.][Pg 261]
The ancient chemists observed that most of the woods, especially themore heavy and compact ones, gave out a particular acid spirit, bydistillation, in a naked fire; but, before Mr Goetling, who gives anaccount of his experiments upon this subject in Crell's Chemical Journalfor 1779, no one had ever made any inquiry into its nature andproperties. This acid appears to be the same, whatever be the wood it isprocured from. When first distilled, it is of a brown colour, andconsiderably impregnated with charcoal and oil; it is purified fromthese by a second distillation. The pyro-lignous radical is chieflycomposed of hydrogen and charcoal.
The name ofPyro-tartarous acid is given to a dilute empyreumatic acidobtained from purified[Pg 262] acidulous tartarite of potash by distillation ina naked fire. To obtain it, let a retort be half filled with powderedtartar, adapt a tubulated recipient, having a bent tube communicatingwith a bell-glass in a pneumato-chemical apparatus; by gradually raisingthe fire under the retort, we obtain the pyro-tartarous acid mixed withoil, which is separated by means of a funnel. A vast quantity ofcarbonic acid gas is disengaged during the distillation. The acidobtained by the above process is much contaminated with oil, which oughtto be separated from it. Some authors advise to do this by a seconddistillation; but the Dijon academicians inform us, that this isattended with great danger from explosions which take place during theprocess.[Pg 263]
| Bases. | Neutral Salts. | ||
| Potash | Pyro-mucite of | potash. | |
| Soda | soda. | ||
| Barytes | barytes. | ||
| Lime | lime. | ||
| Magnesia | magnesia. | ||
| Ammoniac | ammoniac. | ||
| Argill | argill. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| arsenic | arsenic. | ||
| bismuth | bismuth. | ||
| antimony | antimony. | ||
[Note A: All these combinations were unknown to the ancientchemists.—A.][Pg 264]
This acid is obtained by distillation in a naked fire from sugar, andall the saccharine bodies; and, as these substances swell greatly in thefire, it is necessary to leave seven-eighths of the retort empty. It isof a yellow colour, verging to red, and leaves a mark upon the skin,which will not remove but alongst with the epidermis. It may be procuredless coloured, by means of a second distillation, and is concentrated byfreezing, as is directed for the citric acid. It is chiefly composed ofwater and oil slightly oxygenated, and is convertible into oxalic andmalic acids by farther oxygenation with the nitric acid.
It has been pretended that a large quantity of gas is disengaged duringthe distillation of this acid, which is not the case if it be conductedslowly, by means of moderate heat.[Pg 265]
| Bases. | Neutral Salts. | ||
| Lime | Oxalat of | lime. | |
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Argill | argill. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| iron | iron. | ||
| manganese | manganese. | ||
| cobalt | cobalt. | ||
| nickel | nickel. | ||
| lead | lead. | ||
| copper | copper. | ||
| bismuth | bismuth. | ||
| antimony | antimony. | ||
| arsenic | arsenic. | ||
| mercury | mercury. | ||
| silver | silver. | ||
| gold | gold. | ||
| platina | platina. | ||
[Note A: All unknown to the ancient chemists.—A.][Pg 266]
The oxalic acid is mostly prepared in Switzerland and Germany from theexpressed juice of sorrel, from which it cristallizes by being left longat rest; in this state it is partly saturated with potash, forming atrue acidulous oxalat of potash, or salt with excess of acid. To obtainit pure, it must be formed artificially by oxygenating sugar, whichseems to be the true oxalic radical. Upon one part of sugar pour six oreight parts of nitric acid, and apply a gentle heat; a considerableeffervescence takes place, and a great quantity of nitrous gas isdisengaged; the nitric acid is decomposed, and its oxygen unites to thesugar: By allowing the liquor to stand at rest, cristals of pure oxalicacid are formed, which must be dried upon blotting paper, to separateany remaining portions of nitric acid; and, to ensure the purity of theacid, dissolve the cristals in distilled water, and cristallize themafresh.
| Bases. | Neutral salts. | Names of the resulting neutral salts according to the old nomenclature. |
| Barytes | Acetite of barytes | Unknown to the ancients. Discovered by Mr de Morveau, who calls itbarotic acéte. |
| Potash | —— potash | Secret terra foliata tartari of Muller. Arcanum tartari of Basil Valentin and Paracelsus. Purgative magistery of tartar of Schroëder. Essential salt of wine of Zwelfer. Regenerated tartar of Tachenius. Diuretic salt of Sylvius and Wilson. |
| Soda | —— soda | Foliated earth with base of mineral alkali. Mineral or crystallisable foliated earth. Mineral acetous salt. |
| Lime | —— lime | Salt of chalk, coral, or crabs eyes; mentioned by Hartman. |
| Magnesia | —— magnesia | First mentioned by Mr Wenzel. |
| Ammoniac | —— ammoniac | Spiritus Mindereri. Ammoniacal acetous salt. |
| Oxyd of zinc | —— zinc | Known to Glauber, Schwedemberg, Respour, Pott, de Lassone, and Wenzel, but not named. |
| —— manganese | —— manganese | Unknown to the ancients. |
| —— iron | —— iron | Martial vinegar. Described by Monnet, Wenzel, and the Duke d'Ayen. |
| —— lead | —— lead | Sugar, vinegar, and salt of lead or Saturn. |
| —— tin | —— tin | Known to Lemery, Margraff, Monnet, Weslendorf, and Wenzel, but not named. |
| —— cobalt | —— cobalt | Sympathetic ink of Mr Cadet. |
| —— copper | —— copper | Verdigris, crystals of verditer, verditer, distilled verdigris, crystals of Venus or of copper. |
| —— nickel | —— nickel | Unknown to the ancients. |
| —— arsenic | —— arsenic | Arsenico-acetous fuming liquor, liquid phosphorus of Mr Cadet. |
| —— bismuth | —— bismuth | Sugar of bismuth of Mr Geoffroi. Known to Gellert, Pott, Weslendorf, Bergman, and de Morveau. |
| —— mercury | —— mercury | Mercurial foliated earth, Keyser's famous antivenereal remedy. Mentioned by Gebaver in 1748; known to Helot, Margraff, Baumé, Bergman, and de Morveau. |
| —— antimony | —— antimony | Unknown. |
| —— silver | —— silver | Described by Margraff, Monnet, and Wenzel; unknown to the ancients. |
| —— gold | —— gold | Little known, mentioned by Schroëder and Juncker. |
| —— platina | —— platina | Unknown. |
| Argill | —— argill | According to Mr Wenzel, vinegar dissolves only a very small proportion of argill. |
From the liquor remaining after the first cristallization of the oxalicacid we may obtain malic acid by refrigeration: This acid is moreoxygenated than the oxalic; and, by a further oxygenation, the sugar isconvertible into acetous acid, or vinegar.
The oxalic acid, combined with a small quantity of soda or potash, hasthe property, like the tartarous acid, of entering into a number ofcombinations without suffering decomposition: These combinations formtriple salts, or neutral salts with double bases, which ought to haveproper names. The salt of sorrel, which is potash having oxalic acidcombined in excess, is named acidulous oxalat of potash in our newnomenclature.
The acid procured from sorrel has been known to chemists for more than acentury, being mentioned by Mr Duclos in the Memoirs of the Academy for1688, and was pretty accurately described by Boerhaave; but Mr Scheelefirst showed that it contained potash, and demonstrated its identitywith the acid formed by the oxygenation of sugar.
This acid is composed of charcoal and hydrogen united together, andbrought to the state of an acid by the addition of oxygen; it isconsequently formed by the same elements with[Pg 268] the tartarous oxalic,citric, malic acids, and others, but the elements exist in differentproportions in each of these; and it would appear that the acetous acidis in a higher state of oxygenation than these other acids. I have somereason to believe that the acetous radical contains a small portion ofazote; and, as this element is not contained in the radicals of anyvegetable acid except the tartarous, this circumstance is one of thecauses of difference. The acetous acid, or vinegar, is produced byexposing wine to a gentle heat, with the addition of some ferment: Thisis usually the ley, or mother, which has separated from other vinegarduring fermentation, or some similar matter. The spiritous part of thewine, which consists of charcoal and hydrogen, is oxygenated, andconverted into vinegar: This operation can only take place with freeaccess of air, and is always attended by a diminution of the airemployed in consequence of the absorption of oxygen; wherefore, it oughtalways to be carried on in vessels only half filled with the vinousliquor submitted to the acetous fermentation. The acid formed duringthis process is very volatile, is mixed with a large proportion ofwater, and with many foreign substances; and, to obtain it pure, it isdistilled in stone or glass vessels by a gentle fire. The acid whichpasses over in distillation is somewhat changed by the[Pg 269] process, and isnot exactly of the same nature with what remains in the alembic, butseems less oxygenated: This circumstance has not been formerly observedby chemists.
Distillation is not sufficient for depriving this acid of all itsunnecessary water; and, for this purpose, the best way is by exposing itto a degree of cold from 4° to 6° below the freezing point, from 19° to23° of Fahrenheit; by this means the aqueous part becomes frozen, andleaves the acid in a liquid state, and considerably concentrated. In theusual temperature of the air, this acid can only exist in the gasseousform, and can only be retained by combination with a large proportion ofwater. There are other chemical processes for obtaining the acetousacid, which consist in oxygenating the tartarous, oxalic, or malicacids, by means of nitric acid; but there is reason to believe theproportions of the elements of the radical are changed during thisprocess. Mr Hassenfratz is at present engaged in repeating theexperiments by which these conversions are said to be produced.
The combinations of acetous acid with the various salifiable bases arevery readily formed; but most of the resulting neutral salts are notcristallizable, whereas those produced by the tartarous and oxalic acidsare, in general, hardly soluble. Tartarite and oxalat of lime are[Pg 270] notsoluble in any sensible degree: The malats are a medium between theoxalats and acetites, with respect to solubility, and the malic acid isin the middle degree of saturation between the oxalic and acetous acids.With this, as with all the acids, the metals require to be oxydatedprevious to solution.
The ancient chemists knew hardly any of the salts formed by thecombinations of acetous acid with the salifiable bases, except theacetites of potash, soda, ammoniac, copper, and lead. Mr Cadetdiscovered the acetite of arsenic[47]; Mr Wenzel, the Dijon academiciansMr de Lassone, and Mr Proust, made us acquainted with the properties ofthe other acetites. From the property which acetite of potash possesses,of giving out ammoniac in distillation, there is some reason to suppose,that, besides charcoal and hydrogen, the acetous radical contains asmall proportion of azote, though it is not impossible but the aboveproduction of ammoniac may be occasioned by the decomposition of thepotash.
| Bases. | Neutral Salts. | ||
| Barytes | Acetat of | barytes. | |
| Potash | potash. | ||
| Soda | soda. | ||
| Lime | lime. | ||
| Magnesia | magnesia. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | zinc | zinc. | |
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| arsenic | arsenic. | ||
| bismuth | bismuth. | ||
| mercury | mercury. | ||
| antimony | antimony. | ||
| silver | silver. | ||
| gold | gold. | ||
| platina | platina. | ||
| Argill | argill. | ||
Note.—All these salts were unknown to the ancients; and even thosechemists who are most versant in modern discoveries, are yet at a losewhether the greater part of the salts produced by the oxygenated aceticradical belong properly to the class of acetites, or to that ofacetats.—A.[Pg 272]
We have given to radical vinegar the name of acetic acid, from supposingthat it consists of the same radical with that of the acetous acid, butmore highly saturated with oxygen. According to this idea, acetic acidis the highest degree of oxygenation of which the hydro-carbonousradical is susceptible; but, although this circumstance be extremelyprobable, it requires to be confirmed by farther, and more decisiveexperiments, before it be adopted as an absolute chemical truth. Weprocure this acid as follows: Upon three parts acetite of potash or ofcopper, pour one part of concentrated sulphuric acid, and, bydistillation, a very highly concentrated vinegar is obtained, which wecall acetic acid, formerly named radical vinegar. It is not hithertorigorously proved that this acid is more highly oxygenated than theacetous acid, nor that the difference between them may not consist in adifferent proportion between the elements of the radical or base.[Pg 273]
| Bases. | Neutral Salts. | ||
| Barytes | Succinat of | barytes. | |
| Lime | lime. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Magnesia | magnesia. | ||
| Argill | argill. | ||
| Oxyd | of zinc | zinc. | |
| iron | iron. | ||
| manganese | manganese. | ||
| cobalt | cobalt. | ||
| nickel | nickel. | ||
| lead | lead. | ||
| tin | tin. | ||
| copper | copper. | ||
| bismuth | bismuth. | ||
| antimony | antimony. | ||
| arsenic | arsenic. | ||
| mercury | mercury. | ||
| silver | silver. | ||
| gold | gold. | ||
| platina | platina. | ||
Note.—All the succinats were unknown to the ancient chemists.—A.[Pg 274]
The succinic acid is drawn from amber by sublimation in a gentle heat,and rises in a concrete form into the neck of the subliming vessel. Theoperation must not be pushed too far, or by too strong a fire, otherwisethe oil of the amber rises alongst with the acid. The salt is dried uponblotting paper, and purified by repeated solution and crystallization.
This acid is soluble in twenty-four times its weight of cold water, andin a much smaller quantity of hot water. It possesses the qualities ofan acid in a very small degree, and only affects the blue vegetablecolours very slightly. The affinities of this acid, with the salifiablebases, are taken from Mr de Morveau, who is the first chemist that hasendeavoured to ascertain them.[Pg 275]
This acid was known to the ancient chemists under the name of Flowers ofBenjamin, or of Benzoin, and was procured, by sublimation, from the gumor resin called Benzoin: The means of procuring it,via humida, wasdiscovered by Mr Geoffroy, and perfected by Mr Scheele. Upon benzoin,reduced to powder, pour strong lime-water, having rather an excess oflime; keep the mixture continually stirring, and, after half an hour'sdigestion, pour off the liquor, and use fresh portions of lime-water inthe same manner, so long as there is any appearance of neutralization.Join all the decanted liquors, and evaporate, as far as possible,without occasioning cristallization, and, when the liquor is cold, dropin muriatic acid till no more precipitate is formed. By the former partof the process a benzoat of lime is formed, and, by the latter, themuriatic acid combines with the lime, forming muriat of lime, whichremains[Pg 276] dissolved, while the benzoic acid, being insoluble,precipitates in a concrete state.
Camphor is a concrete essential oil, obtained, by sublimation, from aspecies of laurus which grows in China and Japan. By distilling nitricacid eight times from camphor, Mr Kosegarten converted it into an acidanalogous to the oxalic; but, as it differs from that acid in somecircumstances, we have thought necessary to give it a particular name,till its nature be more completely ascertained by farther experiment.
As camphor is a carbono-hydrous or hydro-carbonous radical, it is easilyconceived, that, by oxygenation, it should form oxalic, malic, andseveral other vegetable acids: This conjecture is rendered notimprobable by the experiments of Mr Kosegarten; and the principalphenomena exhibited in the combinations of camphoric acid with thesalifiable bases, being[Pg 277] very similar to those of the oxalic and malicacids, lead me to believe that it consists of a mixture of these twoacids.
The Gallic acid, formerly called Principle of Astringency, is obtainedfrom gall nuts, either by infusion or decoction with water, or bydistillation with a very gentle heat. This acid has only been attendedto within these few years. The Committee of the Dijon Academy havefollowed it through all its combinations, and give the best account ofit hitherto produced. Its acid properties are very weak; it reddens thetincture of turnsol, decomposes sulphurets, and unites to all the metalswhen they have been previously dissolved in some other acid. Iron, bythis combination, is precipitated of a very deep blue or violet colour.The radical of this acid, if it deserves the name of one, is hithertoentirely unknown; it is contained in[Pg 278] oak willow, marsh iris, thestrawberry, nymphea, Peruvian bark, the flowers and bark of pomgranate,and in many other woods and barks.
The only accurate knowledge we have of this acid is from the works of MrScheele. It is contained in whey, united to a small quantity of earth,and is obtained as follows: Reduce whey to one eighth part of its bulkby evaporation, and filtrate, to separate all its cheesy matter; thenadd as much lime as is necessary to combine with the acid; the lime isafterwards disengaged by the addition of oxalic acid, which combineswith it into an insoluble neutral salt. When the oxalat of lime has beenseparated by decantation, evaporate the remaining liquor to theconsistence of honey; the lactic acid is dissolved by alkohol, whichdoes not unite with the sugar of milk and other foreign matters;[Pg 279] theseare separated by filtration from the alkohol and acid; and the alkoholbeing evaporated, or distilled off, leaves the lactic acid behind.
This acid unites with all the salifiable bases forming salts which donot cristallize; and it seems considerably to resemble the acetousacid.[Pg 280]
| Bases. | Neutral Salts. | ||
| Lime | Saccholat of | lime. | |
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Argill | argill. | ||
| Oxyd | of zinc | zinc. | |
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| arsenic | arsenic. | ||
| bismuth | bismuth. | ||
| mercury | mercury. | ||
| antimony | antimony. | ||
| silver | silver. | ||
Note.—All these were unknown to the ancient chemists.—A.[Pg 281]
A species of sugar may be extracted, by evaporation, from whey, whichhas long been known in pharmacy, and which has a considerableresemblance to that procured from sugar canes. This saccharine matter,like ordinary sugar, may be oxygenated by means of nitric acid: For thispurpose, several portions of nitric acid are distilled from it; theremaining liquid is evaporated, and set to cristallize, by which meanscristals of oxalic acid are procured; at the same time a very fine whitepowder precipitates, which is the saccholactic acid discovered byScheele. It is susceptible of combining with the alkalies, ammoniac, theearths, and even with the metals: Its action upon the latter is hithertobut little known, except that, with them, it forms difficultly solublesalts. The order of affinity in the table is taken from Bergman.[Pg 282]
| Bases. | Neutral Salts. | ||
| Barytes | Formiat of | barytes. | |
| Potash | potash. | ||
| Soda | soda. | ||
| Lime | lime. | ||
| Magnesia | magnesia. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| bismuth | bismuth. | ||
| silver | silver. | ||
| Argill | argill. | ||
Note.—All unknown to the ancient chemists.—A.[Pg 283]
This acid was first obtained by distillation from ants, in the lastcentury, by Samuel Fisher. The subject was treated of by Margraff in1749, and by Messrs Ardwisson and Ochrn of Leipsic in 1777. The formicacid is drawn from a large species of red ants,formica rufa, Lin.which form large ant hills in woody places. It is procured, either bydistilling the ants with a gentle heat in a glass retort or an alembic;or, after having washed the ants in cold water, and dried them upon acloth, by pouring on boiling water, which dissolves the acid; or theacid may be procured by gentle expression from the insects, in whichcase it is stronger than in any of the former ways. To obtain it pure,we must rectify, by means of distillation, which separates it from theuncombined oily and charry matter; and it may be concentrated byfreezing, in the manner recommended for treating the acetous acid.[Pg 284]
The juices of the silk worm seem to assume an acid quality when thatinsect changes from a larva to a chrysalis. At the moment of its escapefrom the latter to the butterfly form, it emits a reddish liquor whichreddens blue paper, and which was first attentively observed by MrChaussier of the Dijon academy, who obtains the acid by infusing silkworm chrysalids in alkohol, which dissolves their acid without beingcharged with any of the gummy parts of the insect; and, by evaporatingthe alkohol, the acid remains tollerably pure. The properties andaffinities of this acid are not hitherto ascertained with any precision;and we have reason to believe that analogous acids may be procured fromother insects. The radical of this acid is probably, like that of theother acids from the animal kingdom, composed of charcoal, hydrogen, andazote, with the addition, perhaps, of phosphorus.
| Bases. | Neutral Salts. | ||
| Barytes | Sebat of | barytes. | |
| Potash | potash. | ||
| Soda | soda. | ||
| Lime | lime. | ||
| Magnesia | magnesia. | ||
| Ammoniac | ammoniac. | ||
| Argill | argill. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| arsenic | arsenic. | ||
| bismuth | bismuth. | ||
| mercury | mercury. | ||
| antimony | antimony. | ||
| silver | silver. | ||
Note.—All these were unknown to the ancient chemists.—A.[Pg 286]
To obtain the sebacic acid, let some suet be melted in a skillet overthe fire, alongst with some quick-lime in fine powder, and constantlystirred, raising the fire towards the end of the operation, and takingcare to avoid the vapours, which are very offensive. By this process thesebacic acid unites with the lime into a sebat of lime, which isdifficultly soluble in water; it is, however, separated from the fattymatters with which it is mixed by solution in a large quantity ofboiling water. From this the neutral salt is separated by evaporation;and, to render it pure, is calcined, redissolved, and againcristallized. After this we pour on a proper quantity of sulphuric acid,and the sebacic acid passes over by distillation.[Pg 287]
From the later experiments of Bergman and Scheele, the urinary calculusappears to be a species of salt with an earthy basis; it is slightlyacidulous, and requires a large quantity of water for solution, threegrains being scarcely soluble in a thousand grains of boiling water, andthe greater part again cristallizes when cold. To this concrete acid,which Mr de Morveau calls Lithiasic Acid, we give the name of LithicAcid, the nature and properties of which are hitherto very little known.There is some appearance that it is an acidulous neutral salt, or acidcombined in excess with a salifiable base; and I have reason to believethat it really is an acidulous phosphat of lime; if so, it must beexcluded from the class of peculiar acids.
| Bases. | Neutral Salts. | ||
| Potash | Prussiat of | potash. | |
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Lime | lime. | ||
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Oxyd | of zinc | zinc. | |
| iron | iron. | ||
| manganese | manganese. | ||
| cobalt | cobalt. | ||
| nickel | nickel. | ||
| lead | lead. | ||
| tin | tin. | ||
| copper | copper. | ||
| bismuth | bismuth. | ||
| antimony | antimony. | ||
| arsenic | arsenic. | ||
| silver | silver. | ||
| mercury | mercury. | ||
| gold | gold. | ||
| platina | platina. | ||
Note.—-All these were unknown to former chemists.—A.
As the experiments which have been made hitherto upon this acid seemstill to leave a considerable degree of uncertainty with regard to itsnature, I shall not enlarge upon its properties, and the means ofprocuring it pure and dissengaged from combination. It combines withiron, to which it communicates a blue colour, and is equally susceptibleof entering into combination with most of the other metals, which areprecipitated from it by the alkalies, ammoniac, and lime, in consequenceof greater affinity. The Prussic radical, from the experiments ofScheele, and especially from those of Mr Berthollet, seems composed ofcharcoal and azote; hence it is an acid with a double base. Thephosphorus which has been found combined with it appears, from theexperiments of Mr Hassenfratz, to be only accidental.
Although this acid combines with alkalies, earths, and metals, in thesame way with other acids, it possesses only some of the properties wehave been in use to attribute to acids, and it may consequently beimproperly ranked here in[Pg 290] the class of acids; but, as I have alreadyobserved, it is difficult to form a decided opinion upon the nature ofthis substance until the subject has been farther elucidated by agreater number of experiments.
[36] See Memoirs of the Academy for 1776, p. 671. and for 1778,p. 535,—A.
[37] See Part I. Chap. XI. upon this subject.—A.
[38] See Part I. Chap. XI. upon the application of these namesaccording to the proportions of the two ingredients.—A
[39] See Part I. Chap. XII. upon this subject.—A.
[40] Those who wish to see what has been said upon this greatchemical question by Messrs de Morveau, Berthollet, De Fourcroy, andmyself, may consult our translation of Mr Kirwan's Essay uponPhlogiston.—A.
[41] Saltpetre is likewise procured in large quantities bylixiviating the natural soil in some parts of Bengal, and of the RussianUkrain.—E.
[42] Commonly calledDerbyshire spars.—E.
[43] I have not added the Table of these combinations, as theorder of their affinity is entirely unknown; they are calledmolybdatsof argil,antimony,potash, &c.—E.
[44] This acid was discovered by Mr Scheele, to whom chemistryis indebted for the discovery of several other acids.—A.
[45] I have omitted the Table, as the order of affinity isunknown, and is given by Mr Lavoisier only in alphabetical order. Allthe combinations of malic acid with salifiable bases, which are namedmalats, were unknown to the ancient chemists.—E.
[46] The order of affinity of the salifiable bases with thisacid is hitherto unknown. Mr Lavoisier, from its similarity topyro-lignous acid, supposes the order to be the same in both; but, asthis is not ascertained by experiment, the table is omitted. All thesecombinations, calledPyro-tartarites, were unknown till lately—E.
[47] Savans Etrangers, Vol. III.
[48] These combinations are called Benzoats of Lime, Potash,Zinc, &c.; but, as the order of affinity is unknown, the alphabeticaltable is omitted, as unnecessary.—E.
[49] These combinations, which were all unknown to theancients, are called Camphorats. The table is omitted, as being only inalphabetical order.—E.
[50] These combinations, which are called Gallats, were allunknown to the ancients; and the order of their affinity is not hithertoestablished.—A.
[51] These combinations are called Lactats; they were allunknown to the ancient chemists, and their affinities have not yet beenascertained.—A.
[52] These combinations named Bombats were unknown to theancient chemists; and the affinities of the salifiable bases with thebombic acid are hitherto undetermined.—A.
[53] All the combinations of this acid, should it finally turnout to be one, were unknown to the ancient chemists, and its affinitieswith the salifiable bases have not been hitherto determined.—A.
In the two former parts of this work I designedly avoided beingparticular in describing the manual operations of chemistry, because Ihad found from experience, that, in a work appropriated to reasoning,minute descriptions of processes and of plates interrupt the chain ofideas, and render the attention necessary both difficult and tedious tothe reader. On the other hand, if I had confined myself to the summarydescriptions hitherto given, beginners could have only acquired veryvague conceptions of practical chemistry from my work, and must havewanted both confidence and interest in operations they could neitherrepeat nor[Pg 292] thoroughly comprehend. This want could not have beensupplied from books; for, besides that there are not any which describethe modern instruments and experiments sufficiently at large, any workthat could have been consulted would have presented these things under avery different order of arrangement, and in a different chemicallanguage, which must greatly tend to injure the main object of myperformance.
Influenced by these motives, I determined to reserve, for a third partof my work, a summary description of all the instruments andmanipulations relative to elementary chemistry. I considered it asbetter placed at the end, rather than at the beginning of the book,because I must have been obliged to suppose the reader acquainted withcircumstances which a beginner cannot know, and must therefore have readthe elementary part to become acquainted with. The whole of this thirdpart may therefore be considered as resembling the explanations ofplates which are usually placed at the end of academic memoirs, thatthey may not interrupt the connection of the text by lengtheneddescription. Though I have taken great pains to render this part clearand methodical, and have not omitted any essential instrument orapparatus, I am far from pretending by it to set aside the necessity ofattendance upon lectures and laboratories,[Pg 293] for such as wish to acquireaccurate knowledge of the science of chemistry. These should familiarisethemselves to the employment of apparatus, and to the performance ofexperiments by actual experience.Nihil est in intellectu quod nonprius fuerit in sensu, the motto which the celebrated Rouelle caused tobe painted in large characters in a conspicuous part of his laboratory,is an important truth never to be lost sight of either by teachers orstudents of chemistry.
Chemical operations may be naturally divided into several classes,according to the purposes they are intended for performing. Some may beconsidered as purely mechanical, such as the determination of the weightand bulk of bodies, trituration, levigation, searching, washing,filtration, &c. Others may be considered as real chemical operations,because they are performed by means of chemical powers and agents; suchare solution, fusion, &c. Some of these are intended for separating theelements of bodies from each other, some for reuniting these elementstogether; and some, as combustion, produce both these effects during thesame process.
Without rigorously endeavouring to follow the above method, I mean togive a detail of the chemical operations in such order of arrangement asseemed best calculated for conveying[Pg 294] instruction. I shall be moreparticular in describing the apparatus connected with modern chemistry,because these are hitherto little known by men who have devoted much oftheir time to chemistry, and even by many professors of the science.
The best method hitherto known for determining the quantities ofsubstances submitted to chemical experiment, or resulting from them, isby means of an accurately constructed beam and scales, with properlyregulated weights, which well known operation is calledweighing. Thedenomination and quantity of the weights used as an unit or standard forthis purpose are extremely arbitrary, and vary not only in differentkingdoms, but even in different provinces of the same kingdom, and indifferent cities of the same province. This variation is of infiniteconsequence to be well understood in commerce and in the arts; but, inchemistry, it is of no moment what particular denomination of weight beemployed, provided the results of experiments be expressed in convenientfractions of the same denomination. For this purpose, until all theweights used in society be reduced to the same standard, it will besufficient for chemists in different parts to use the common[Pg 296] pound oftheir own country as the unit or standard, and to express all itsfractional parts in decimals, instead of the arbitrary divisions now inuse. By this means the chemists of all countries will be thoroughlyunderstood by each other, as, although the absolute weights of theingredients and products cannot be known, they will readily, and withoutcalculation, be able to determine the relative proportions of these toeach other with the utmost accuracy; so that in this way we shall bepossessed of an universal language for this part of chemistry.
With this view I have long projected to have the pound divided intodecimal fractions, and I have of late succeeded through the assistanceof Mr Fourche balance-maker at Paris, who has executed it for me withgreat accuracy and judgment. I recommend to all who carry on experimentsto procure similar divisions of the pound, which they will find botheasy and simple in its application, with a very small knowledge ofdecimal fractions[54].
As the usefulness and accuracy of chemistry depends entirely upon thedetermination of the weights of the ingredients and products both beforeand after experiments, too much precision cannot be employed in thispart of the subject; and, for this purpose, we must be provided withgood instruments. As we are often obliged, in chemical processes, toascertain, within a grain or less, the tare or weight of large and heavyinstruments, we must have beams made with peculiar niceness by accurateworkmen, and these must always be kept apart from the laboratory in someplace where the vapours of acids, or other corrosive liquors, cannothave access, otherwise the steel will rust, and the accuracy of thebalance be destroyed. I have three sets, of different sizes, made by MrFontin with the utmost nicety, and, excepting those made by Mr Ramsdenof London, I do not think any can compare with them for precision andsensibility. The largest of these is about three feet long in the beamfor large weights, up to fifteen or twenty pounds; the second, forweights of eighteen or twenty ounces, is exact to a tenth part of agrain; and the smallest, calculated only for weighing about one gros, issensibly affected by the five hundredth part of a grain.
Besides these nicer balances, which are only used for experiments ofresearch, we must have[Pg 298] others of less value for the ordinary purposesof the laboratory. A large iron balance, capable of weighing forty orfifty pounds within half a dram, one of a middle size, which mayascertain eight or ten pounds, within ten or twelve grains, and a smallone, by which about a pound may be determined, within one grain.
We must likewise be provided with weights divided into their severalfractions, both vulgar and decimal, with the utmost nicety, and verifiedby means of repeated and accurate trials in the nicest scales; and itrequires some experience, and to be accurately acquainted with thedifferent weights, to be able to use them properly. The best way ofprecisely ascertaining the weight of any particular substance is toweigh it twice, once with the decimal divisions of the pound, andanother time with the common subdivisions or vulgar fractions, and, bycomparing these, we attain the utmost accuracy.
By the specific gravity of any substance is understood the quotient ofits absolute weight divided by its magnitude, or, what is the same, theweight of a determinate bulk of any body. The weight of a determinatemagnitude of water has been generally assumed as unity for this purpose;and we express the specific gravity of gold, sulphuric acid, &c. bysaying, that gold is nineteen times, and sulphuric acid twice the weightof water, and so of other bodies.[Pg 299]
It is the more convenient to assume water as unity in specificgravities, that those substances whose specific gravity we wish todetermine, are most commonly weighed in water for that purpose. Thus, ifwe wish to determine the specific gravity of gold flattened under thehammer, and supposing the piece of gold to weigh8 oz. 4 gros 2-1/2grs. in the air[55], it is suspended by means of a fine metallic wireunder the scale of a hydrostatic balance, so as to be entirely immersedin water, and again weighed. The piece of gold in Mr Brisson'sexperiment lost by this means3 gros 37 grs.; and, as it is evidentthat the weight lost by a body weighed in water is precisely equal tothe weight of the water displaced, or to that of an equal volume ofwater, we may conclude, that, in equal magnitudes, gold weighs4893-1/2grs. and water253 grs. which, reduced to unity, gives 1.0000 as thespecific gravity of water, and 19.3617 for that of gold. We may operatein the same manner with all solid substances. We have rarely anyoccasion, in chemistry, to determine the specific gravity of solidbodies, unless when operating upon alloys or metallic glasses; but wehave very frequent necessity to ascertain that of fluids, as it is oftenthe only means of judging of their purity or degree of concentration.
This object may be very fully accomplished with the hydrostatic balance,by weighing a solid body; such, for example, as a little ball of rockcristal suspended by a very fine gold wire, first in the air, andafterwards in the fluid whose specific gravity we wish to discover. Theweight lost by the cristal, when weighed in the liquor, is equal to thatof an equal bulk of the liquid. By repeating this operation successivelyin water and different fluids, we can very readily ascertain, by asimple and easy calculation, the relative specific gravities of thesefluids, either with respect to each other or to water. This method isnot, however, sufficiently exact, or, at least, is rather troublesome,from its extreme delicacy, when used for liquids differing but little inspecific gravity from water; such, for instance, as mineral waters, orany other water containing very small portions of salt in solution.
In some operations of this nature, which have not hitherto been madepublic, I employed an instrument of great sensibility for this purposewith great advantage. It consists of a hollow cylinder,A b c f, Pl.vii. fig. 6. of brass, or rather of silver, loaded at its bottom, b c f,with tin, as represented swimming in a jug of water,l m n o. To theupper part of the cylinder is attached a stalk of silver wire, not morethan three fourths of a line diameter, surmounted by[Pg 301] a little cupd,intended for containing weights; upon the stalk a mark is made atg,the use of which we shall presently explain. This cylinder may be madeof any size; but, to be accurate, ought at least to displace four poundsof water. The weight of tin with which this instrument is loaded oughtto be such as will make it remain almost in equilibrium in distilledwater, and should not require more than half a dram, or a dram at most,to make it sink tog.
We must first determine, with great precision, the exact weight of theinstrument, and the number of additional grains requisite for making itsink, in distilled water of a determinate temperature, to the mark: Wethen perform the same experiment upon all the fluids of which we wish toascertain the specific gravity, and, by means of calculation, reduce theobserved differences to a common standard of cubic feet, pints orpounds, or of decimal fractions, comparing them with water. This method,joined to experiments with certain reagents[56], is one of the best fordetermining the quality of waters, and is even capable of pointing outdifferences which escape the most accurate chemical analysis. I shall,at some future[Pg 302] period, give an account of a very extensive set ofexperiments which I have made upon this subject.
These metallic hydrometers are only to be used for determining thespecific gravities of such waters as contain only neutral salts oralkaline substances; and they may be constructed with different degreesof ballast for alkohol and other spiritous liquors. When the specificgravities of acid liquors are to be ascertained, we must use a glasshydrometer, as represented Pl. vii. fig. 14[57]. This consists of ahollow cylinder of glass,a b c f, hermetically sealed at its lowerend, and drawn out at the upper into a capillary tubea, ending in thelittle cup or basond. This instrument is ballasted with more or lessmercury, at the bottom of the cylinder introduced through the tube, inproportion to the weight of the liquor intended to be examined: We mayintroduce a small graduated slip of paper into the tubea d; and,though these degrees do not exactly correspond to the fractions ofgrains in the different liquors, they may be rendered very useful incalculation.
What is said in this chapter may suffice, without farther enlargement,for indicating the[Pg 303] means of ascertaining the absolute and specificgravities of solids and fluids, as the necessary instruments aregenerally known, and may easily be procured: But, as the instruments Ihave used for measuring the gasses are not any where described, I shallgive a more detailed account of these in the following chapter.
[54] Mr Lavoisier gives, in this part of his work, veryaccurate directions for reducing the common subdivisions of the Frenchpound into decimal fractions, andvice versa, by means of tablessubjoined to this 3d part. As these instructions, and the table, wouldbe useless to the British chemist, from the difference between thesubdivisions of the French and Troy pounds, I have omitted them, buthave subjoined in the appendix accurate rules for converting the oneinto the other.—E.
[55] Vide Mr Brisson's Essay upon Specific Gravity, p. 5.—A.
[56] For the use of these reagents see Bergman's excellenttreatise upon the analysis of mineral waters, in his Chemical andPhysical Essays.—E.
[57] Three or four years ago, I have seen similar glasshydrometers, made for Dr Black by B. Knie, a very ingenious artist ofthis city.—E.
The French chemists have of late applied the name ofpneumato-chemicalapparatus to the very simple and ingenious contrivance, invented by DrPriestley, which is now indispensibly necessary to every laboratory.This consists of a wooden trough, of larger or smaller dimensions as isthought convenient, lined with plate-lead or tinned copper, asrepresented in perspective, Pl. V. In Fig. 1. the same trough or cisternis supposed to have two of its sides cut away, to show its interiorconstruction more distinctly. In this apparatus, we distinguish betweenthe shelf ABCD Fig. 1. and 2. and the bottom or body of the cistern FGHIFig. 2.[Pg 305] The jars or bell-glasses are filled with water in this deeppart, and, being turned with their mouths downwards, are afterwards setupon the shelf ABCD, as shown Plate X. Fig. 1. F. The upper parts of thesides of the cistern above the level of the shelf are called therimorborders.
The cistern ought to be filled with water, so as to stand at least aninch and a half deep upon the shelf, and it should be of such dimensionsas to admit of at least one foot of water in every direction in thewell. This size is sufficient for ordinary occasions; but it is oftenconvenient, and even necessary, to have more room; I would thereforeadvise such as intend to employ themselves usefully in chemicalexperiments, to have this apparatus made of considerable magnitude,where their place of operating will allow. The well of my principalcistern holds four cubical feet of water, and its shelf has a surface offourteen square feet; yet, in spite of this size, which I at firstthought immoderate, I am often straitened for room.
In laboratories, where a considerable number of experiments areperformed, it is necessary to have several lesser cisterns, besides thelarge one, which may be called thegeneral magazine; and even someportable ones, which may be moved when necessary, near a furnace, orwherever they may be wanted. There are likewise some operations whichdirty the water of the apparatus,[Pg 306] and therefore require to be carriedon in cisterns by themselves.
It were doubtless considerably cheaper to use cisterns, or iron-boundtubs, of wood simply dove-tailed, instead of being lined with lead orcopper; and in my first experiments I used them made in that way; but Isoon discovered their inconvenience. If the water be not always kept atthe same level, such of the dovetails as are left dry shrink, and, whenmore water is added, it escapes through the joints, and runs out.
We employ cristal jars or bell glasses, Pl. V. Fig. 9. A. for containingthe gasses in this apparatus; and, for transporting these, when full ofgas, from one cistern to another, or for keeping them in reserve whenthe cistern is too full, we make use of a flat dish BC, surrounded by astanding up rim or border, with two handles DE for carrying it by.
After several trials of different materials, I have found marble thebest substance for constructing the mercurial pneumato-chemicalapparatus, as it is perfectly impenetrable by mercury, and is notliable, like wood, to separate at the junctures, or to allow the mercuryto escape through chinks; neither does it run the risk of breaking, likeglass, stone-ware, or porcelain. Take a block of marble BCDE, Plate V.Fig. 3. and 4. about two feet long, 15 or 18 inches[Pg 307] broad, and teninches thick, and cause it to be hollowed out as atm n Fig. 5. aboutfour inches deep, as a reservoir for the mercury; and, to be able moreconveniently to fill the jars, cut the gutter T V, Fig. 3. 4. and 5. atleast four inches deeper; and, as this trench may sometimes provetroublesome, it is made capable of being covered at pleasure by thinboards, which slip into the groovesx y, Fig. 5. I have two marblecisterns upon this construction, of different sizes, by which I canalways employ one of them as a reservoir of mercury, which it preserveswith more safety than any other vessel, being neither subject tooverturn, nor to any other accident. We operate with mercury in thisapparatus exactly as with water in the one before described; but thebell-glasses must be of smaller diameter, and much stronger; or we mayuse glass tubes, having their mouths widened, as in Fig. 7.; these arecalledeudiometers by the glass-men who sell them. One of thebell-glasses is represented Fig. 5. A. standing in its place, and whatis called a jar is engraved Fig. 6.
The mercurial pneumato-chemical apparatus is necessary in allexperiments wherein the disengaged gasses are capable of being absorbedby water, as is frequently the case, especially in all combinations,excepting those of metals, in fermentation,[Pg 308]&c.
I give the name ofgazometer to an instrument which I invented, andcaused construct, for the purpose of a kind of bellows, which mightfurnish an uniform and continued stream of oxygen gas in experiments offusion. Mr Meusnier and I have since made very considerable correctionsand additions, having converted it into what may be called anuniversalinstrument, without which it is hardly possible to perform most of thevery exact experiments. The name we have given the instrument indicatesits intention for measuring the volume or quantity of gas submitted toit for examination.
It consists of a strong iron beam, DE, Pl. VIII. Fig. 1. three feetlong, having at each end, D and E, a segment of a circle, likewisestrongly constructed of iron, and very firmly joined. Instead of beingpoised as in ordinary balances, this beam rests, by means of acylindrical axis of polished steel, F, Fig. 9. upon two large moveablebrass friction-wheels, by which the resistance to its motion fromfriction is considerably diminished, being converted into friction[Pg 309] ofthe second order. As an additional precaution, the parts of these wheelswhich support the axis of the beam are covered with plates of polishedrock-cristal. The whole of this machinery is fixed to the top of thesolid column of wood BC, Fig. 1. To one extremity D of the beam, a scaleP for holding weights is suspended by a flat chain, which applies to thecurvature of the arcnDo, in a groove made for the purpose. To theother extremity E of the beam is applied another flat chain,i k m, soconstructed, as to be incapable of lengthening or shortening, by beingless or more charged with weight; to this chain, an iron trivet, withthree branches,a i,c i, andh i, is strongly fixed ati, andthese branches support a large inverted jar A, of hammered copper, ofabout 18 inches diameter, and 20 inches deep. The whole of this machineis represented in perspective, Pl. VIII. Fig. 1. and Pl. IX. Fig. 2. and4. give perpendicular sections, which show its interior structure.
Round the bottom of the jar, on its outside, is fixed (Pl. IX. Fig. 2.)a border divided into compartments 1, 2, 3, 4, &c. intended to receiveleaden weights separately represented 1, 2, 3, Fig. 3. These areintended for increasing the weight of the jar when a considerablepressure is requisite, as will be afterwards explained, though suchnecessity seldom occurs.[Pg 310] The cylindrical jar A is entirely open below,de, Pl. IX. Fig. 4.; but is closed above with a copper lid,a b c,open atb f, and capable of being shut by the cock g. This lid, as maybe seen by inspecting the figures, is placed a few inches within the topof the jar to prevent the jar from being ever entirely immersed in thewater, and covered over. Were I to have this instrument made over again,I should cause the lid to be considerably more flattened, so as to bealmost level. This jar or reservoir of air is contained in thecylindrical copper vessel, LMNO, Pl. VIII. Fig. 1. filled with water.
In the middle of the cylindrical vessel LMNO, Pl. IX. Fig. 4. are placedtwo tubesst, xy, which are made to approach each other at their upperextremitiest y; these are made of such a length as to rise a littleabove the upper edge LM of the vessel LMNO, and when the jarabcdetouches the bottom NO, their upper ends enter about half an inch intothe conical hollowb, leading to the stop-cockg.
The bottom of the vessel LMNO is represented Pl. IX. Fig. 3. in themiddle of which a small hollow semispherical cap is soldered, which maybe considered as the broad end of a funnel reversed; the two tubesst,xy, Fig. 4. are adapted to this cap ats andx, and by this meanscommunicate with the tubesmm, nn, oo, pp, Fig. 3. which are fixedhorizontally upon the[Pg 311] bottom of the vessel, and all of which terminatein, and are united by, the spherical capsx. Three of these tubes arecontinued out of the vessel, as in Pl. VIII. Fig. 1. The first marked inthat figure 1, 2, 3, is inserted at its extremity 3, by means of anintermediate stop-cock 4, to the jar V. which stands upon the shelf of asmall pneumato-chemical apparatus GHIK, the inside of which is shown Pl.IX. Fig. 1. The second tube is applied against the outside of the vesselLMNO from 6 to 7, is continued at 8, 9, 10, and at 11 is engaged belowthe jar V. The former of these tubes is intended for conveying gas intothe machine, and the latter for conducting small quantities for trialsunder jars. The gas is made either to flow into or out of the machine,according to the degree of pressure it receives; and this pressure isvaried at pleasure, by loading the scale P less or more, by means ofweights. When gas is to be introduced into the machine, the pressure istaken off, or even rendered negative; but, when gas is to be expelled, apressure is made with such degree of force as is found necessary.
The third tube 12, 13, 14, 15, is intended for conveying air or gas toany necessary place or apparatus for combustions, combinations, or anyother experiment in which it is required.
To explain the use of the fourth tube, I must enter into somediscussions. Suppose the vessel[Pg 312] LMNO, Pl. VIII. Fig. 1. full of water,and the jar A partly filled with gas, and partly with water; it isevident that the weights in the bason P may be so adjusted, as tooccasion an exact equilibrium between the weight of the bason and of thejar, so that the external air shall not tend to enter into the jar, northe gas to escape from it; and in this case the water will stand exactlyat the same level both within and without the jar. On the contrary, ifthe weight in the bason P be diminished, the jar will then pressdownwards from its own gravity, and the water will stand lower withinthe jar than it does without; in this case, the included air or gas willsuffer a degree of compression above that experienced by the externalair, exactly proportioned to the weight of a column of water, equal tothe difference of the external and internal surfaces of the water. Fromthese reflections, Mr Meusnier contrived a method of determining theexact degree of pressure to which the gas contained in the jar is at anytime exposed. For this purpose, he employs a double glass syphon 19, 20,21, 22, 23, firmly cemented at 19 and 23. The extremity 19 of thissyphon communicates freely with the water in the external vessel of themachine, and the extremity 23 communicates with the fourth tube at thebottom of the cylindrical vessel, and consequently, by means of theperpendicular[Pg 313] tubest, Pl. IX. Fig. 4. with the air contained in thejar. He likewise cements, at 16, Pl. VIII. Fig. 1. another glass tube16, 17, 18, which communicates at 16 with the water in the exteriorvessel LMNO, and, at its upper end 18, is open to the external air.
By these several contrivances, it is evident that the water must standin the tube 16, 17, 18, at the same level with that in the cistern LMNO;and, on the contrary, that, in the branch 19, 20, 21, it must standhigher or lower, according as the air in the jar is subjected to agreater or lesser pressure than the external air. To ascertain thesedifferences, a brass scale divided into inches and lines is fixedbetween these two tubes. It is readily conceived that, as air, and allother elastic fluids, must increase in weight by compression, it isnecessary to know their degree of condensation to be enabled tocalculate their quantities, and to convert the measure of their volumesinto correspondent weights; and this object is intended to be fulfilledby the contrivance now described.
But, to determine the specific gravity of air or of gasses, and toascertain their weight in a known volume, it is necessary to know theirtemperature, as well as the degree of pressure under which they subsist;and this is accomplished by means of a small thermometer, stronglycemented into a brass collet, which screws[Pg 314] into the lid of the jar A.This thermometer is represented separately, Pl. VIII. Fig. 10. and inits place 24, 25, Fig. 1. and Pl. IX. Fig. 4. The bulb is in the insideof the jar A, and its graduated stalk rises on the outside of the lid.
The practice of gazometry would still have laboured under greatdifficulties, without farther precautions than those above described.When the jar A sinks in the water of the cistern LMNO, it must lose aweight equal to that of the water which it displaces; and consequentlythe compression which it makes upon the contained air or gas must beproportionally diminished. Hence the gas furnished, during experimentsfrom the machine, will not have the same density towards the end that ithad at the beginning, as its specific gravity is continuallydiminishing. This difference may, it is true, be determined bycalculation; but this would have occasioned such mathematicalinvestigations as must have rendered the use of this apparatus bothtroublesome and difficult. Mr Meusnier has remedied this inconvenienceby the following contrivance. A square rod of iron, 26, 27, Pl. VIII.Fig. 1. is raised perpendicular to the middle of the beam DE. This rodpasses through a hollow box of brass 28, which opens, and may be filledwith lead; and this box is made to slide alongst the rod, by means of atoothed pinion playing in a rack, so as to raise[Pg 315] or lower the box, andto fix it at such places as is judged proper.
When the lever or beam DE stands horizontal, this box gravitates toneither side; but, when the jar A sinks into the cistern LMNO, so as tomake the beam incline to that side, it is evident the loaded box 28,which then passes beyond the center of suspension, must gravitate to theside of the jar, and augment its pressure upon the included air. This isincreased in proportion as the box is raised towards 27, because thesame weight exerts a greater power in proportion to the length of thelever by which it acts. Hence, by moving the box 28 alongst the rod 26,27, we can augment or diminish the correction it is intended to makeupon the pressure of the jar; and both experience and calculation showthat this may be made to compensate very exactly for the loss of weightin the jar at all degrees of pressure.
I have not hitherto explained the most important part of the use of thismachine, which is the manner of employing it for ascertaining thequantities of the air or gas furnished during experiments. To determinethis with the most rigorous precision, and likewise the quantitysupplied to the machine from experiments, we fixed to the arc whichterminates the arm of the beam E, Pl. VIII. Fig. 1. the brass sectorlm, divided into degrees and half degrees,[Pg 316] which consequently moves incommon with the beam; and the lowering of this end of the beam ismeasured by the fixed index 29, 30, which has a Nonius giving hundredthparts of a degree at its extremity 30.
The whole particulars of the different parts of the above describedmachine are represented in Plate VIII. as follow.
Fig. 2. Is the flat chain invented by Mr Vaucanson, and employed forsuspending the scale or bason P, Fig. 1; but, as this lengthens orshortens according as it is more or less loaded, it would not haveanswered for suspending the jar A, Fig. 1.
Fig. 5. Is the chaini k m, which in Fig. 1. sustains the jar A. Thisis entirely formed of plates of polished iron interlaced into eachother, and held together by iron pins. This chain does not lengthen inany sensible degree, by any weight it is capable of supporting.
Fig. 6. The trivet, or three branched stirrup, by which the jar A ishung to the balance, with the screw by which it is fixed in anaccurately vertical position.
Fig. 3. The iron rod 26, 27, which is fixed perpendicular to the centerof the beam, with its box 28.
Fig. 7. & 8. The friction-wheels, with the plates of rock-cristal Z, aspoints of contact[Pg 317] by which the friction of the axis of the lever of thebalance is avoided.
Fig. 4. The piece of metal which supports the axis of thefriction-wheels.
Fig. 9. The middle of the lever or beam, with the axis upon which itmoves.
Fig. 10. The thermometer for determining the temperature of the air orgas contained in the jar.
When this gazometer is to be used, the cistern or external vessel, LMNO,Pl. VIII. Fig. 1. is to be filled with water to a determinate height,which should be the same in all experiments. The level of the watershould be taken when the beam of the balance stands horizontal; thislevel, when the jar is at the bottom of the cistern, is increased by allthe water which it displaces, and is diminished in proportion as the jarrises to its highest elevation. We next endeavour, by repeated trials,to discover at what elevation the box 28 must be fixed, to render thepressure equal in all situations of the beam. I should have said nearly,because this correction is not absolutely rigorous; and differences of aquarter, or even of half a line, are not of any consequence. This heightof the box 28 is not the same for every degree of pressure, but variesaccording as this is of one, two, three, or more inches. All theseshould be registered with great order and precision.[Pg 318]
We next take a bottle which holds eight or ten pints, the capacity ofwhich is very accurately determined by weighing the water it is capableof containing. This bottle is turned bottom upwards, full of water, inthe cistern of the pneumato chemical apparatus GHIK, Fig. 1. and is seton its mouth upon the shelf of the apparatus, instead of the glass jarV, having the extremity 11 of the tube 7, 8, 9, 10, 11, inserted intoits mouth. The machine is fixed at zero of pressure, and the degreemarked by the index 30 upon the sectorm l is accurately observed;then, by opening the stop-cock 8, and pressing a little upon the jar A,as much air is forced into the bottle as fills it entirely. The degreemarked by the index upon the sector is now observed, and we calculatewhat number of cubical inches correspond to each degree. We then fill asecond and third bottle, and so on, in the same manner, with the sameprecautions, and even repeat the operation several times with bottles ofdifferent sizes, till at last, by accurate attention, we ascertain theexact gage or capacity of the jar A, in all its parts; but it is betterto have it formed at first accurately cylindrical, by which we avoidthese calculations and estimates.
The instrument I have been describing was constructed with greataccuracy and uncommon skill by Mr Meignie junior, engineer and physical[Pg 319]instrument-maker. It is a most valuable instrument, from the greatnumber of purposes to which it is applicable; and, indeed, there aremany experiments which are almost impossible to be performed without it.It becomes expensive, because, in many experiments, such as theformation of water and of nitric acid, it is absolutely necessary toemploy two of the same machines. In the present advanced state ofchemistry, very expensive and complicated instruments are becomeindispensibly necessary for ascertaining the analysis and synthesis ofbodies with the requisite precision as to quantity and proportion; it iscertainly proper to endeavour to simplify these, and to render them lesscostly; but this ought by no means to be attempted at the expence oftheir conveniency of application, and much less of their accuracy.
The gazometer described in the foregoing section is too costly and toocomplicated for being generally used in laboratories for measuring thegasses, and is not even applicable to every[Pg 320] circumstance of this kind.In numerous series of experiments, more simple and more readilyapplicable methods must be employed. For this purpose I shall describethe means I used before I was in possession of a gazometer, and which Istill use in preference to it in the ordinary course of my experiments.
Suppose that, after an experiment, there is a residuum of gas, neitherabsorbable by alkali nor water, contained in the upper part of the jarAEF, Pl. IV. Fig. 3. standing on the shelf of a pneumato-chemicalapparatus, of which we wish to ascertain the quantity, we must firstmark the height to which the mercury or water rises in the jar withgreat exactness, by means of slips of paper pasted in several partsround the jar. If we have been operating in mercury, we begin bydisplacing the mercury from the jar, by introducing water in its stead.This is readily done by filling a bottle quite full of water; havingstopped it with your finger, turn it up, and introduce its mouth belowthe edge of the jar; then, turning down its body again, the mercury, byits gravity, falls into the bottle, and the water rises in the jar, andtakes the place occupied by the mercury. When this is accomplished, pourso much water into the cistern ABCD as will stand about an inch over thesurface of the mercury; then pass the dish BC, Pl. V. Fig. 9. under thejar, and carry it to the[Pg 321] water cistern, Fig. 1. and 2. We here exchangethe gas into another jar, which has been previously graduated in themanner to be afterwards described; and we thus judge of the quantity orvolume of the gas by means of the degrees which it occupies in thegraduated jar.
There is another method of determining the volume of gas, which mayeither be substituted in place of the one above described, or may beusefully employed as a correction or proof of that method. After the airor gas is exchanged from the first jar, marked with slips of paper, intothe graduated jar, turn up the mouth of the marked jar, and fill it withwater exactly to the marks EF, Pl. IV. Fig. 3. and by weighing the waterwe determine the volume of the air or gas it contained, allowing onecubical foot, or 1728 cubical inches, of water for each 70 pounds,French weight.
The manner of graduating jars for this purpose is very easy, and weought to be provided with several of different sizes, and even severalof each size, in case of accidents. Take a tall, narrow, and strongglass jar, and, having filled it with water in the cistern, Pl. V. Fig.1. place it upon the shelf ABCD; we ought always to use the same placefor this operation, that the level of the shelf may be always exactlysimilar, by which almost the only error to which this process is liablewill be avoided. Then take a narrow[Pg 322] mouthed phial which holds exactly 6oz. 3gros 61grs. of water, which corresponds to 10 cubicalinches. If you have not one exactly of this dimension, choose one alittle larger, and diminish its capacity to the size requisite, bydropping in a little melted wax and rosin. This bottle serves thepurpose of a standard for gaging the jars. Make the air contained inthis bottle pass into the jar, and mark exactly the place to which thewater has descended; add another measure of air, and again mark theplace of the water, and so on, till all the water be displaced. It is ofgreat consequence that, during the course of this operation, the bottleand jar be kept at the same temperature with the water in the cistern;and, for this reason, we must avoid keeping the hands upon either asmuch as possible; or, if we suspect they have been heated, we must coolthem by means of the water in the cistern. The height of the barometerand thermometer during this experiment is of no consequence.
When the marks have been thus ascertained upon the jar for every tencubical inches, we engrave a scale upon one of its sides, by means of adiamond pencil. Glass tubes are graduated in the same manner for usingin the mercurial apparatus, only they must be divided into cubicalinches, and tenths of a cubical inch. The bottle used for gaging thesemust hold[Pg 323] 8oz. 6gros 25grs. of mercury, which exactlycorresponds to a cubical inch of that metal.
The method of determining the volume of air or gas, by means of agraduated jar, has the advantage of not requiring any correction for thedifference of height between the surface of the water within the jar,and in the cistern; but it requires corrections with respect to theheight of the barometer and thermometer. But, when we ascertain thevolume of air by weighing the water which the jar is capable ofcontaining, up to the marks EF, it is necessary to make a farthercorrection, for the difference between the surface of the water in thecistern, and the height to which it rises within the jar. This will beexplained in the fifth section of this chapter.
As experiments often produce two, three, or more species of gas, it isnecessary to be able to separate these from each other, that we mayascertain the quantity and species of each. Suppose that under the jarA, Pl. IV. Fig. 3. is[Pg 324] contained a quantity of different gasses mixedtogether, and standing over mercury, we begin by marking with slips ofpaper, as before directed, the height at which the mercury stands withinthe glass; then introduce about a cubical inch of water into the jar,which will swim over the surface of the mercury: If the mixture of gascontains any muriatic or sulphurous acid gas, a rapid and considerableabsorption will instantly take place, from the strong tendency these twogasses have, especially the former, to combine with, or be absorbed bywater. If the water only produces a slight absorption of gas hardlyequal to its own bulk, we conclude, that the mixture neither containsmuriatic acid, sulphuric acid, or ammoniacal gas, but that it containscarbonic acid gas, of which water only absorbs about its own bulk. Toascertain this conjecture, introduce some solution of caustic alkali,and the carbonic acid gas will be gradually absorbed in the course of afew hours; it combines with the caustic alkali or potash, and theremaining gas is left almost perfectly free from any sensible residuumof carbonic acid gas.
After each experiment of this kind, we must carefully mark the height atwhich the mercury stands within the jar, by slips of paper pasted on,and varnished over when dry, that they may not be washed off when placedin the water apparatus.[Pg 325] It is likewise necessary to register thedifference between the surface of the mercury in the cistern and that inthe jar, and the height of the barometer and thermometer, at the end ofeach experiment.
When all the gas or gasses absorbable by water and potash are absorbed,water is admitted into the jar to displace the mercury; and, as isdescribed in the preceding section, the mercury in the cistern is to becovered by one or two inches of water. After this, the jar is to betransported by means of the flat dish BC, Pl. V. Fig. 9. into the waterapparatus; and the quantity of gas remaining is to be ascertained bychanging it into a graduated jar. After this, small trials of it are tobe made by experiments in little jars, to ascertain nearly the nature ofthe gas in question. For instance, into a small jar full of the gas,Fig. 8. Pl. V. a lighted taper is introduced; if the taper is notimmediately extinguished, we conclude the gas to contain oxygen gas;and, in proportion to the brightness of the flame, we may judge if itcontain less or more oxygen gas than atmospheric air contains. If, onthe contrary, the taper be instantly extinguished, we have strong reasonto presume that the residuum is chiefly composed of azotic gas. If, uponthe approach of the taper, the gas takes fire and burns quietly at thesurface with a white flame, we conclude it to be[Pg 326] pure hydrogen gas; ifthis flame is blue, we judge it consists of carbonated hydrogen gas;and, if it takes fire with a sudden deflagration, that it is a mixtureof oxygen and hydrogen gas. If, again, upon mixing a portion of theresiduum with oxygen gas, red fumes are produced, we conclude that itcontains nitrous gas.
These preliminary trials give some general knowledge of the propertiesof the gas, and nature of the mixture, but are not sufficient todetermine the proportions and quantities of the several gasses of whichit is composed. For this purpose all the methods of analysis must beemployed; and, to direct these properly, it is of great use to have aprevious approximation by the above methods. Suppose, for instance, weknow that the residuum consists of oxygen and azotic gas mixed together,put a determinate quantity, 100 parts, into a graduated tube of ten ortwelve lines diameter, introduce a solution of sulphuret of potash incontact with the gas, and leave them together for some days; thesulphuret absorbs the whole oxygen gas, and leaves the azotic gas pure.
If it is known to contain hydrogen gas, a determinate quantity isintroduced into Volta's eudiometer alongst with a known proportion ofhydrogen gas; these are deflagrated together by means of the electricalspark; fresh portions of oxygen gas are successively added, till nofarther[Pg 327] deflagration takes place, and till the greatest possiblediminution is produced. By this process water is formed, which isimmediately absorbed by the water of the apparatus; but, if the hydrogengas contain charcoal, carbonic acid is formed at the same time, which isnot absorbed so quickly; the quantity of this is readily ascertained byassisting its absorption, by means of agitation. If the residuumcontains nitrous gas, by adding oxygen gas, with which it combines intonitric acid, we can very nearly ascertain its quantity, from thediminution produced by this mixture.
I confine myself to these general examples, which are sufficient to givean idea of this kind of operations; a whole volume would not serve toexplain every possible case. It is necessary to become familiar with theanalysis of gasses by long experience; we must even acknowledge thatthey mostly possess such powerful affinities to each other, that we arenot always certain of having separated them completely. In these cases,we must vary our experiments in every possible point of view, add newagents to the combination, and keep out others, and continue our trials,till we are certain of the truth and exactitude of our conclusions.[Pg 328]
All elastic fluids are compressible or condensible in proportion to theweight with which they are loaded. Perhaps this law, which isascertained by general experience, may suffer some irregularity whenthese fluids are under a degree of condensation almost sufficient toreduce them to the liquid state, or when either in a state of extremerarefaction or condensation; but we seldom approach either of theselimits with most of the gasses which we submit to our experiments. Iunderstand this proposition of gasses being compressible, in proportionto their superincumbent weights, as follows:
A barometer, which is an instrument generally known, is, properlyspeaking, a species of syphon, ABCD, Pl. XII. Fig. 16. whose leg AB isfilled with mercury, whilst the leg CD is full of air. If we suppose thebranch CD indefinitely continued till it equals the height of ouratmosphere, we can readily conceive that the barometer is, in reality, asort of balance, in which[Pg 329] a column of mercury stands in equilibriumwith a column of air of the same weight. But it is unnecessary toprolongate the branch CD to such a height, as it is evident that thebarometer being immersed in air, the column of mercury AB will beequally in equilibrium with a column of air of the same diameter, thoughthe leg CD be cut off at C, and the part CD be taken away altogether.
The medium height of mercury in equilibrium with the weight of a columnof air, from the highest part of the atmosphere to the surface of theearth is about twenty-eight French inches in the lower parts of the cityof Paris; or, in other words, the air at the surface of the earth atParis is usually pressed upon by a weight equal to that of a column ofmercury twenty-eight inches in height. I must be understood in this wayin the several parts of this publication when talking of the differentgasses, as, for instance, when the cubical foot of oxygen gas is said toweigh 1oz. 4gros, under 28 inches pressure. The height of thiscolumn of mercury, supported by the pressure of the air, diminishes inproportion as we are elevated above the surface of the earth, or ratherabove the level of the sea, because the mercury can only form anequilibrium with the column of air which is above it, and is not in thesmallest[Pg 330] degree affected by the air which is below its level.
In what ratio does the mercury in the barometer descend in proportion toits elevation? or, what is the same thing, according to what law orratio do the several strata of the atmosphere decrease in density? Thisquestion, which has exercised the ingenuity of natural philosophersduring last century, is considerably elucidated by the followingexperiment.
If we take the glass syphon ABCDE, Pl. XII. Fig. 17. shut at E, and openat A, and introduce a few drops of mercury, so as to intercept thecommunication of air between the leg AB and the leg BE, it is evidentthat the air contained in BCDE is pressed upon, in common with the wholesurrounding air, by a weight or column of air equal to 28 inches ofmercury. But, if we pour 28 inches of mercury into the leg AB, it isplain the air in the branch BCDE will now be pressed upon by a weightequal to twice 28 inches of mercury, or twice the weight of theatmosphere; and experience shows, that, in this case, the included air,instead of filling the tube from B to E, only occupies from C to E, orexactly one half of the space it filled before. If to this first columnof mercury we add two other portions of 28 inches each, in the branchAB, the air in the branch BCDE will be pressed upon by four times theweight of the[Pg 331] atmosphere, or four times the weight of 28 inches ofmercury, and it will then only fill the space from D to E, or exactlyone quarter of the space it occupied at the commencement of theexperiment. From these experiments, which may be infinitely varied, hasbeen deduced as a general law of nature, which seems applicable to allpermanently elastic fluids, that they diminish in volume in proportionto the weights with which they are pressed upon; or, in other words,"the volume of all elastic fluids is in the inverse ratio of the weightby which they are compressed."
The experiments which have been made for measuring the heights ofmountains by means of the barometer, confirm the truth of thesedeductions; and, even supposing them in some degree inaccurate, thesedifferences are so extremely small, that they may be reckoned asnullities in chemical experiments. When this law of the compression ofelastic fluids is once well understood, it becomes easily applicable tothe corrections necessary in pneumato chemical experiments upon thevolume of gas, in relation to its pressure. These corrections are of twokinds, the one relative to the variations of the barometer, and theother for the column of water or mercury contained in the jars. I shallendeavour to explain these by examples, beginning with the most simplecase.[Pg 332]
Suppose that 100 cubical inches of oxygen gas are obtained at 10°(54.5°) of the thermometer, and at 28 inches 6 lines of the barometer,it is required to know what volume the 100 cubical inches of gas wouldoccupy, under the pressure of 28 inches[58], and what is the exactweight of the 100 inches of oxygen gas? Let the unknown volume, or thenumber of inches this gas would occupy at 28 inches of the barometer, beexpressed byx; and, since the volumes are in the inverse ratio oftheir superincumbent weights, we have the following statement: 100cubical inches is tox inversely as 28.5 inches of pressure is to 28.0inches; or directly 28 : 28.5 :: 100 :x = 101.786—cubical inches, at28 inches barometrical pressure; that is to say, the same gas or airwhich at 28.5 inches of the barometer occupies 100 cubical inches ofvolume, will occupy 101.786 cubical inches when the barometer is at 28inches. It is equally easy to calculate the weight of this gas,occupying 100 cubical inches, under 28.5 inches of barometricalpressure; for, as it corresponds[Pg 333] to 101.786 cubical inches at thepressure of 28, and as, at this pressure, and at 10° (54.5°) oftemperature, each cubical inch of oxygen gas weighs half a grain, itfollows, that 100 cubical inches, under 28.5 barometrical pressure, mustweigh 50.893 grains. This conclusion might have been formed moredirectly, as, since the volume of elastic fluids is in the inverse ratioof their compression, their weights must be in the direct ratio of thesame compression: Hence, since 100 cubical inches weigh 50 grains, underthe pressure of 28 inches, we have the following statement to determinethe weight of 100 cubical inches of the same gas as 28.5 barometricalpressure, 28 : 50 :: 28.5 :x, the unknown quantity, = 50.893.
The following case is more complicated: Suppose the jar A, Pl. XII. Fig.18. to contain a quantity of gas in its upper part ACD, the rest of thejar below CD being full of mercury, and the whole standing in themercurial bason or reservoir GHIK, filled with mercury up to EF, andthat the difference between the surface CD of the mercury in the jar,and EF, that in the cistern, is six inches, while the barometer standsat 27.5 inches. It is evident from these data, that the air contained inACD is pressed upon by the weight of the atmosphere, diminished by theweight of the column of mercury CE, or by 27.5 - 6 = 21.5 inches ofbarometrical[Pg 334] pressure. This air is therefore less compressed than theatmosphere at the mean height of the barometer, and consequentlyoccupies more space than it would occupy at the mean pressure, thedifference being exactly proportional to the difference between thecompressing weights. If, then, upon measuring the space ACD, it is foundto be 120 cubical inches, it must be reduced to the volume which itwould occupy under the mean pressure of 28 inches. This is done by thefollowing statement: 120 :x, the unknown volume, :: 21.5 : 28inversely; this givesx = 120 × 21.5 / 28 = 92.143 cubical inches.
In these calculations we may either reduce the height of the mercury inthe barometer, and the difference of level in the jar and bason, intolines or decimal fractions of the inch; but I prefer the latter, as itis more readily calculated. As, in these operations, which frequentlyrecur, it is of great use to have means of abbreviation, I have given atable in the appendix for reducing lines and fractions of lines intodecimal fractions of the inch.
In experiments performed in the water-apparatus, we must make similarcorrections to procure rigorously exact results, by taking into account,and making allowances for the difference of height of the water withinthe jar above the surface of the water in the cistern. But, as the[Pg 335]pressure of the atmosphere is expressed in inches and lines of themercurial barometer, and, as homogeneous quantities only can becalculated together, we must reduce the observed inches and lines ofwater into correspondent heights of the mercury. I have given a table inthe appendix for this conversion, upon the supposition that mercury is13.5681 times heavier than water.
In ascertaining the weight of gasses, besides reducing them to a mean ofbarometrical pressure, as directed in the preceding section, we mustlikewise reduce them to a standard thermometrical temperature; because,all elastic fluids being expanded by heat, and condensed by cold, theirweight in any determinate volume is thereby liable to considerablealterations. As the temperature of 10° (54.5°) is a medium between theheat of summer and the cold of winter, being the temperature ofsubterraneous places, and that which is most easily approached to at allseasons, I have chosen that degree as a mean to which I reduce air orgas in this species of calculation.[Pg 336]
Mr de Luc found that atmospheric air was increased 1/215 part of itsbulk, by each degree of a mercurial thermometer, divided into 81degrees, between the freezing and boiling points; this gives 1/211 partfor each degree of Reaumur's thermometer, which is divided into 80degrees between these two points. The experiments of Mr Monge seem tomake this dilatation less for hydrogen gas, which he thinks is onlydilated 1/180. We have not any exact experiments hitherto publishedrespecting the ratio of dilatation of the other gasses; but, from thetrials which have been made, their dilatation seems to differ littlefrom that of atmospheric air. Hence I may take for granted, till fartherexperiments give us better information upon this subject, thatatmospherical air is dilated 1/210 part, and hydrogen gas 1/190 part foreach degree of the thermometer; but, as there is still great uncertaintyupon this point, we ought always to operate in a temperature as near aspossible to the standard of 10°, (54.5°) by this means any errors incorrecting the weight or volume of gasses by reducing them to the commonstandard, will become of little moment.
The calculation for this correction is extremely easy. Divide theobserved volume of air by 210, and multiply the quotient by the degreesof temperature above or below 10°[Pg 337] (54.5°). This correction is negativewhen the actual temperature is above the standard, and positive whenbelow. By the use of logarithmical tables this calculation is muchfacilitated[59].
In the jar A, Pl. IV. Fig. 3. standing in a water apparatus, iscontained 353 cubical inches of air; the surface of the water within thejar at EF is 4-1/2 inches above the water in the cistern, the barometeris at 27 inches 9-1/2 lines, and the thermometer at 15° (65.75°). Havingburnt a quantity of phosphorus in the air, by which concrete phosphoricacid is produced, the air after the combustion occupies 295 cubical[Pg 338]inches, the water within the jar stands 7 inches above that in thecistern, the barometer is at 27 inches 9-1/4 lines, and the thermometerat 16° (68°). It is required from these data to determine the actualvolume of air before and after combustion, and the quantity absorbedduring the process.
The air in the jar before combustion was 353 cubical inches, but it wasonly under a barometrical pressure of 27 inches 9-1/2 lines; which,reduced to decimal fractions by Tab. I. of the Appendix, gives 27.79167inches; and from this we must deduct the difference of 4-1/2 inches ofwater, which, by Tab. II. corresponds to 0.33166 inches of thebarometer; hence the real pressure of the air in the jar is 27.46001. Asthe volume of elastic fluids diminish in the inverse ratio of thecompressing weights, we have the following statement to reduce the 353inches to the volume the air would occupy at 28 inches barometricalpressure.
353 :x, the unknown volume, :: 27.46001 : 28. Hence,x = 353 ×27.46001 / 28 = 346.192 cubical inches, which is the volume the samequantity of air would have occupied at 28 inches of the barometer.[Pg 339]
The 210th part of this corrected volume is 1.65, which, for the fivedegrees of temperature above the standard gives 8.255 cubical inches;and, as this correction is subtractive, the real corrected volume of theair before combustion is 337.942 inches.
By a similar calculation upon the volume of air after combustion, wefind its barometrical pressure 27.77083 - 0.51593 = 27.25490. Hence, tohave the volume of air under the pressure of 28 inches, 295 :x ::27.77083 : 28 inversely; or,x = 295 x 27.25490 / 28 = 287.150. The210th part of this corrected volume is 1.368, which, multiplied by 6degrees of thermometrical difference, gives the subtractive correctionfor temperature 8.208, leaving the actual corrected volume of air aftercombustion 278.942 inches.
| The corrected volume before combustion | 337.942 |
| Ditto remaining after combustion | 278.942 |
| ———— | |
| Volume absorbed during combustion | 59.000. |
Take a large balloon A, Pl. V. Fig. 10. capable of holding 17 or 18pints, or about half a cubical foot, having the brass capbcdestrongly cemented to its neck, and to which the tube and stop-cockf gis fixed by a tight screw. This apparatus is connected by the doublescrew represented separately at Fig. 12. to the jar BCD, Fig. 10. whichmust be some pints larger in dimensions than the balloon. This jar isopen at top, and is furnished with the brass caph i, and stop-cocklm. One of these slop-cocks is represented separately at Fig. 11.
We first determine the exact capacity of the balloon by filling it withwater, and weighing it both full and empty. When emptied of water, it isdried with a cloth introduced through its neckd e, and the lastremains of moisture are removed by exhausting it once or twice in anair-pump.
When the weight of any gas is to be ascertained, this apparatus is usedas follows: Fix the balloon A to the plate of an air-pump by means ofthe screw of the stop-cockf g, which is[Pg 341] left open; the balloon is tobe exhausted as completely as possible, observing carefully the degreeof exhaustion by means of the barometer attached to the air-pump. Whenthe vacuum is formed, the stop-cockf g is shut, and the weight of theballoon determined with the most scrupulous exactitude. It is then fixedto the jar BCD, which we suppose placed in water in the shelf of thepneumato chemical apparatus Fig. 1.; the jar is to be filled with thegas we mean to weigh, and then, by opening the stop-cocksf g andlm, the gas ascends into the balloon, whilst the water of the cisternrises at the same time into the jar. To avoid very troublesomecorrections, it is necessary, during this first part of the operation,to sink the jar in the cistern till the surfaces of the water within thejar and without exactly correspond. The stop-cocks are again shut, andthe balloon being unscrewed from its connection with the jar, is to becarefully weighed; the difference between this weight and that of theexhausted balloon is the precise weight of the air or gas contained inthe balloon. Multiply this weight by 1728, the number of cubical inchesin a cubical foot, and divide the product by the number of cubicalinches contained in the balloon, the quotient is the weight of a cubicalfoot of the gas or air submitted to experiment.[Pg 342]
Exact account must be kept of the barometrical height and temperature ofthe thermometer during the above experiment; and from these theresulting weight of a cubical foot is easily corrected to the standardof 28 inches and 10°, as directed in the preceding section. The smallportion of air remaining in the balloon after forming the vacuum mustlikewise be attended to, which is easily determined by the barometerattached to the air-pump. If that barometer, for instance, remains atthe hundredth part of the height it stood at before the vacuum wasformed, we conclude that one hundredth part of the air originallycontained remained in the balloon, and consequently that only 99/100 ofgas was introduced from the jar into the balloon.
[58] According to the proportion of 114 to 107, given betweenthe French and English foot, 28 inches of the French barometer are equalto 29.83 inches of the English. Directions will be found in the appendixfor converting all the French weights and measures used in this workinto corresponding English denominations.—E.
[59] When Fahrenheit's thermometeris employed, the dilatation by each degree must be smaller, in theproportion of 1 to 2.25, because each degree of Reaumur's scale contains2.25 degrees of Fahrenheit; hence we must divide by 472.5, and finishthe rest of the calculation as above.—E.
The calorimeter, or apparatus for measuring the relative quantities ofheat contained in bodies, was described by Mr de la Place and me in theMemoirs of the Academy for 1780, p. 355. and from that Essay thematerials of this chapter are extracted.
If, after having cooled any body to the freezing point, it be exposed inan atmosphere of 25° (88.25°), the body will gradually become heated,from the surface inwards, till at last it acquire the same temperaturewith the surrounding air. But, if a piece of ice be placed in the samesituation, the circumstances are quite different; it does not approachin the smallest degree towards the temperature of the circumambient air,but remains constantly at Zero (32°), or the temperature of melting ice,till the last portion of ice be completely melted.
This phenomenon is readily explained; as, to melt ice, or reduce it towater, it requires to be combined with a certain portion of caloric;[Pg 344]the whole caloric attracted from the surrounding bodies, is arrested orfixed at the surface or external layer of ice which it is employed todissolve, and combines with it to form water; the next quantity ofcaloric combines with the second layer to dissolve it into water, and soon successively till the whole ice be dissolved or converted into waterby combination with caloric, the very last atom still remaining at itsformer temperature, because the caloric has never penetrated so far aslong as any intermediate ice remained to melt.
Upon these principles, if we conceive a hollow sphere of ice at thetemperature of Zero (32°) placed in an atmosphere 10° (54.5°), andcontaining a substance at any degree of temperature above freezing, itfollows, 1st, That the heat of the external atmosphere cannot penetrateinto the internal hollow of the sphere of ice; 2dly, That the heat ofthe body placed in the hollow of the sphere cannot penetrate outwardsbeyond it, but will be stopped at the internal surface, and continuallyemployed to melt successive layers of ice, until the temperature of thebody be reduced to Zero (32°), by having all its superabundant caloricabove that temperature carried off by the ice. If the whole water,formed within the sphere of ice during the reduction of the temperatureof the included body to Zero, be carefully collected, the weight[Pg 345] of thewater will be exactly proportional to the quantity of caloric lost bythe body in passing from its original temperature to that of meltingice; for it is evident that a double quantity of caloric would havemelted twice the quantity of ice; hence the quantity of ice melted is avery exact measure of the quantity of caloric employed to produce thateffect, and consequently of the quantity lost by the only substance thatcould possibly have supplied it.
I have made this supposition of what would take place in a hollow sphereof ice, for the purpose of more readily explaining the method used inthis species of experiment, which was first conceived by Mr de la Place.It would be difficult to procure such spheres of ices and inconvenientto make use of them when got; but, by means of the following apparatus,we have remedied that defect. I acknowledge the name of Calorimeter,which I have given it, as derived partly from Greek and partly fromLatin, is in some degree open to criticism; but, in matters of science,a slight deviation from strict etymology, for the sake of givingdistinctness of idea, is excusable; and I could not derive the nameentirely from Greek without approaching too near to the names of knowninstruments employed for other purposes.
The calorimeter is represented in Pl. VI. It is shown in perspective atFig. 1. and its interior[Pg 346] structure is engraved in Fig. 2. and 3.; theformer being a horizontal, and the latter a perpendicular section. Itscapacity or cavity is divided into three parts, which, for betterdistinction, I shall name the interior, middle, and external cavities.The interior cavityf f f f, Fig. 4. into which the substancessubmitted to experiment are put, is composed of a grating or cage ofiron wire, supported by several iron bars; its opening or mouth LM, iscovered by the lid HG, of the same materials. The middle cavityb b bb, Fig. 2. and 3. is intended to contain the ice which surrounds theinterior cavity, and which is to be melted by the caloric of thesubstance employed in the experiment. The ice is supported by the gratem m at the bottom of the cavity, under which is placed the sievenn. These two are represented separately in Fig. 5. and 6.
In proportion as the ice contained in the middle cavity is melted, bythe caloric disengaged from the body placed in the interior cavity, thewater runs through the grate and sieve, and falls through the conicalfunnelc c d, Fig. 3. and tubex y, into the receiver F, Fig. 1.This water may be retained or let out at pleasure, by means of thestop-cocku. The external cavitya a a a, Fig. 2. and 3. is filledwith ice, to prevent any effect upon the ice in the middle cavity fromthe heat of the surrounding air, and[Pg 347] the water produced from it iscarried off through the pipe ST, which shuts by means of the stop-cockr. The whole machine is covered by the lid FF, Fig. 7. made of tinpainted with oil colour, to prevent rust.
When this machine is to be employed, the middle cavityb b b b, Fig.2. and 3., the lid GH, Fig. 4. of the interior cavity, the externalcavitya a a a, Fig. 2. and 3. and the general lid FF, Fig. 7. are allfilled with pounded ice, well rammed, so that no void spaces remain, andthe ice of the middle cavity is allowed to drain. The machine is thenopened, and the substance submitted to experiment being placed in theinterior cavity, it is instantly closed. After waiting till the includedbody is completely cooled to the freezing point, and the whole meltedice has drained from the middle cavity, the water collected in thevessel F, Fig. 1. is accurately weighed. The weight of the waterproduced during the experiment is an exact measure of the caloricdisengaged during the cooling of the included body, as this substance isevidently in a similar situation with the one formerly mentioned asincluded in a hollow sphere of ice; the whole caloric disengaged isstopped by the ice in the middle cavity, and that ice is preserved frombeing affected by any other heat by means of the ice contained in thegeneral lid, Fig. 7. and in the external cavity. Experiments[Pg 348] of thiskind last from fifteen to twenty hours; they are sometimes acceleratedby covering up the substance in the interior cavity with well drainedice, which hastens its cooling.
The substances to be operated upon are placed in the thin iron bucket,Fig. 8. the cover of which has an opening fitted with a cork, into whicha small thermometer is fixed. When we use acids, or other fluids capableof injuring the metal of the instruments, they are contained in thematras, Fig. 10. which has a similar thermometer in a cork fitted to itsmouth, and which stands in the interior cavity upon the smallcylindrical support RS, Fig. 10.
It is absolutely requisite that there be no communication between theexternal and middle cavities of the calorimeter, otherwise the icemelted by the influence of the surrounding air, in the external cavity,would mix with the water produced from the ice of the middle cavity,which would no longer be a measure of the caloric lost by the substancesubmitted to experiment.
When the temperature of the atmosphere is only a few degrees above thefreezing point, its heat can hardly reach the middle cavity, beingarrested by the ice of the cover, Fig. 7. and of the external cavity;but, if the temperature of the air be under the degree of freezing, itmight cool the ice contained in the middle cavity, by[Pg 349] causing the icein the external cavity to fall, in the first place, below zero (32°). Itis therefore essential that this experiment be carried on in atemperature somewhat above freezing: Hence, in time of frost, thecalorimeter must be kept in an apartment carefully heated. It islikewise necessary that the ice employed be not under zero (32°); forwhich purpose it must be pounded, and spread out thin for some time, ina place of a higher temperature.
The ice of the interior cavity always retains a certain quantity ofwater adhering to its surface, which may be supposed to belong to theresult of the experiment; but as, at the beginning of each experiment,the ice is already saturated with as much water as it can contain, ifany of the water produced by the caloric should remain attached to theice, it is evident, that very nearly an equal quantity of what adheredto it before the experiment must have run down into the vessel F in itsstead; for the inner surface of the ice in the middle cavity is verylittle changed during the experiment.
By any contrivance that could be devised, we could not prevent theaccess of the external air into the interior cavity when the atmospherewas 9° or 10° (52° or 54°) above zero. The air confined in the cavitybeing in that case specifically heavier than the external air, escapesdownwards through the pipex y, Fig. 3, and is[Pg 350] replaced by the warmerexternal air, which, giving out its caloric to the ice, becomes heavier,and sinks in its turn; thus a current of air is formed through themachine, which is the more rapid in proportion as the external airexceeds the internal in temperature. This current of warm air must melta part of the ice, and injure the accuracy of the experiment: We may, ina great degree, guard against this source of error by keeping thestop-cocku continually shut; but it is better to operate only whenthe temperature of the external air does not exceed 3°, or at most 4°,(39° to 41°); for we have observed, that, in this case, the melting ofthe interior ice by the atmospheric air is perfectly insensible; so thatwe may answer for the accuracy of our experiments upon the specific heatof bodies to a fortieth part.
We have caused make two of the above described machines; one, which isintended for such experiments as do not require the interior air to berenewed, is precisely formed according to the description here given;the other, which answers for experiments upon combustion, respiration,&c. in which fresh quantities of air are indispensibly necessary,differs from the former in having two small tubes in the two lids, bywhich a current of atmospheric air may be blown into the interior cavityof the machine.[Pg 351]
It is extremely easy, with this apparatus, to determine the phenomenawhich occur in operations where caloric is either disengaged orabsorbed. If we wish, for instance, to ascertain the quantity of caloricwhich is disengaged from a solid body in cooling a certain number ofdegrees, let its temperature be raised to 80° (212°); it is then placedin the interior cavityf f f f, Fig. 2. and 3. of the calorimeter, andallowed to remain till we are certain that its temperature is reduced tozero (32°); the water produced by melting the ice during its cooling iscollected, and carefully weighed; and this weight, divided by the volumeof the body submitted to experiment, multiplied into the degrees oftemperature which it had above zero at the commencement of theexperiment, gives the proportion of what the English philosophers callspecific heat.
Fluids are contained in proper vessels, whose specific heat has beenpreviously ascertained, and operated upon in the machine in the samemanner as directed for solids, taking care to deduct, from the quantityof water melted during the experiment, the proportion which belongs tothe containing vessel.
If the quantity of caloric disengaged during the combination ofdifferent substances is to be determined, these substances are to bepreviously reduced to the freezing degree by keeping[Pg 352] them a sufficienttime surrounded with pounded ice; the mixture is then to be made in theinner cavity of the calorimeter, in a proper vessel likewise reduced tozero (32°); and they are kept inclosed till the temperature of thecombination has returned to the same degree: The quantity of waterproduced is a measure of the caloric disengaged during the combination.
To determine the quantity of caloric disengaged during combustion, andduring animal respiration, the combustible bodies are burnt, or theanimals are made to breathe in the interior cavity, and the waterproduced is carefully collected. Guinea pigs, which resist the effectsof cold extremely well, are well adapted for this experiment. As thecontinual renewal of air is absolutely necessary in such experiments, weblow fresh air into the interior cavity of the calorimeter by means of apipe destined for that purpose, and allow it to escape through anotherpipe of the same kind; and that the heat of this air may not produceerrors in the results of the experiments, the tube which conveys it intothe machine is made to pass through pounded ice, that it may be reducedto zero (32°) before it arrives at the calorimeter. The air whichescapes must likewise be made to pass through a tube surrounded withice, included in the interior cavity of the machine, and the water whichis produced must make a part of what is[Pg 353] collected, because the caloricdisengaged from this air is part of the product of the experiment.
It is somewhat more difficult to determine the specific caloriccontained in the different gasses, on account of their small degree ofdensity; for, if they are only placed in the calorimeter in vessels likeother fluids, the quantity of ice melted is so small, that the result ofthe experiment becomes at best very uncertain. For this species ofexperiment we have contrived to make the air pass through two metallicworms, or spiral tubes; one of these, through which the air passes, andbecomes heated in its way to the calorimeter, is contained in a vesselfull of boiling water, and the other, through which the air circulateswithin the calorimeter to disengage its caloric, is placed in theinterior cavity,f f f f, of that machine. By means of a smallthermometer placed at one end of the second worm, the temperature of theair, as it enters the calorimeter, is determined, and its temperature ingetting out of the interior cavity is found by another thermometerplaced at the other end of the worm. By this contrivance we are enabledto ascertain the quantity of ice melted by determinate quantities of airor gas, while losing a certain number of degrees of temperature, and,consequently, to determine their several degrees of specific caloric.The[Pg 354] same apparatus, with some particular precautions, may be employedto ascertain the quantity of caloric disengaged by the condensation ofthe vapours of different liquids.
The various experiments which may be made with the calorimeter do notafford absolute conclusions, but only give us the measure of relativequantities; we have therefore to fix a unit, or standard point, fromwhence to form a scale of the several results. The quantity of caloricnecessary to melt a pound of ice has been chosen as this unit; and, asit requires a pound of water of the temperature of 60° (167°) to melt apound of ice, the quantity of caloric expressed by our unit or standardpoint is what raises a pound of water from zero (32°) to 60° (167°).When this unit is once determined, we have only to express thequantities of caloric disengaged from different bodies by cooling acertain number of degrees, in analogous values: The following is an easymode of calculation for this purpose, applied to one of our earliestexperiments.
We took 7lib. 11oz. 2gros 36grs. of plate-iron, cut intonarrow slips, and rolled up, or expressing the quantity in decimals,7.7070319. These, being heated in a bath of boiling water to about 78°(207.5°), were quickly introduced into the interior cavity of thecalorimeter: At[Pg 355] the end of eleven hours, when the whole quantity ofwater melted from the ice had thoroughly drained off, we found that1.109795 pounds of ice were melted. Hence, the caloric disengaged fromthe iron by cooling 78° (175.5°) having melted 1.109795 pounds of ice,how much would have been melted by cooling 60° (135°)? This questiongives the following statement in direct proportion, 78 : 1.109795 :: 60: x = 0.85369. Dividing this quantity by the weight of the whole ironemployed, viz. 7.7070319, the quotient 0.110770 is the quantity of icewhich would have been melted by one pound of iron whilst cooling through60° (135°) of temperature.
Fluid substances, such as sulphuric and nitric acids, &c. are containedin a matras, Pl. VI. Fig. 9. having a thermometer adapted to the cork,with its bulb immersed in the liquid. The matras is placed in a bath ofboiling water, and when, from the thermometer, we judge the liquid israised to a proper temperature, the matras is placed in the calorimeter.The calculation of the products, to determine the specific caloric ofthese fluids, is made as above directed, taking care to deduct from thewater obtained the quantity which would have been produced by the matrasalone, which must be ascertained by a previous experiment. The[Pg 356] table ofthe results obtained by these experiments is omitted, because not yetsufficiently complete, different circumstances having occasioned theseries to be interrupted; it is not, however, lost sight of; and we areless or more employed upon the subject every winter.
These are, properly speaking, only preliminary mechanical operations fordividing and separating the particles of bodies, and reducing them intovery fine powder. These operations can never reduce substances intotheir primary, or elementary and ultimate particles; they do not evendestroy the aggregation of bodies; for every particle, after the mostaccurate trituration, forms a small whole, resembling the original massfrom which it was divided. The real chemical operations, on thecontrary, such as solution, destroy the aggregation of bodies, andseparate their constituent and integrant particles from each other.[Pg 358]
Brittle substances are reduced to powder by means of pestles andmortars. These are of brass or iron, Pl. I. Fig. 1.; of marble orgranite, Fig. 2.; of lignum vitae, Fig. 3.; of glass, Fig. 4.; of agate,Fig. 5.; or of porcellain, Fig. 6. The pestles for each of these arerepresented in the plate, immediately below the mortars to which theyrespectively belong, and are made of hammered iron or brass, of wood,glass, porcellain, marble, granite, or agate, according to the nature ofthe substances they are intended to triturate. In every laboratory, itis requisite to have an assortment of these utensils, of various sizesand kinds: Those of porcellain and glass can only be used for rubbingsubstances to powder, by a dexterous use of the pestle round the sidesof the mortar, as it would be easily broken by reiterated blows of thepestle.
The bottom of mortars ought to be in the form of a hollow sphere, andtheir sides should have such a degree of inclination as to make thesubstances they contain fall back to the bottom when the pestle islifted, but not so perpendicular as to collect them too much together,otherwise too large a quantity would get below the pestle, and preventits operation. For this reason, likewise, too large a quantity of thesubstance to be powdered ought not to be put into the mortar at onetime; and we must from[Pg 359] time to time get rid of the particles alreadyreduced to powder, by means of sieves to be afterwards described.
The most usual method of levigation is by means of a flat table ABCD,Pl. 1. Fig. 7. of porphyry, or other stone of similar hardness, uponwhich the substance to be reduced to powder is spread, and is thenbruised and rubbed by a muller M, of the same hard materials, the bottomof which is made a small portion of a large sphere; and, as the mullertends continually to drive the substances towards the sides of thetable, a thin flexible knife, or spatula of iron, horn, wood, or ivory,is used for bringing them back to the middle of the stone.
In large works, this operation is performed by means of large rollers ofhard stone, which turn upon each other, either horizontally, in the wayof corn-mills, or by one vertical roller turning upon a flat stone. Inthe above operations, it is often requisite to moisten the substances alittle, to prevent the fine powder from flying off.
There are many bodies which cannot be reduced to powder by any of theforegoing methods; such are fibrous substances, as woods; such as aretough and elastic, as the horns of animals, elastic gum, &c. and themalleable metals which flatten under the pestle, instead of beingreduced to powder. For reducing the[Pg 360] woods to powder, rasps, as Pl. I.Fig. 8. are employed; files of a finer kind are used for horn, and stillfiner, Pl. 1. Fig. 9. and 10. for metals.
Some of the metals, though not brittle enough to powder under thepestle, are too soft to be filed, as they clog the file, and prevent itsoperation. Zinc is one of these, but it may be powdered when hot in aheated iron mortar, or it may be rendered brittle, by alloying it with asmall quantity of mercury. One or other of these methods is used byfire-work makers for producing a blue flame by means of zinc. Metals maybe reduced into grains, by pouring them when melted into water, whichserves very well when they are not wanted in fine powder.
Fruits, potatoes, &c. of a pulpy and fibrous nature may be reduced topulp by means of the grater, Pl. 1. Fig. 11.
The choice of the different substances of which these instruments aremade is a matter of importance; brass or copper are unfit for operationsupon substances to be used as food or in pharmacy; and marble ormetallic instruments must not be used for acid substances; hence mortarsof very hard wood, and those of porcelain, granite, or glass, are ofgreat utility in many operations.[Pg 361]
None of the mechanical operations employed for reducing bodies to powderis capable of producing it of an equal degree of fineness throughout;the powder obtained by the longest and most accurate trituration beingstill an assemblage of particles of various sizes. The coarser of theseare removed, so as only to leave the finer and more homogeneousparticles by means of sieves, Pl. I. Fig. 12. 13. 14. 15. of differentfinenesses, adapted to the particular purposes they are intended for;all the powdered matter which is larger than the intestices of the sieveremains behind, and is again submitted to the pestle, while the finerpass through. The sieve Fig. 12. is made of hair-cloth, or of silkgauze; and the one represented Fig. 13. is of parchment pierced withround holes of a proper size; this latter is employed in the manufactureof gun-powder. When very subtile or valuable materials are to be sifted,which are easily dispersed, or when the finer parts of the powder may behurtful, a compound sieve, Fig. 15. is made use of, which consists ofthe sieve ABCD, with a lid EF, and receiver GH; these three[Pg 362] parts arerepresented as joined together for use, Fig. 14.
There is a method of procuring powders of an uniform fineness,considerably more accurate than the sieve; but it can only be used withsuch substances as are not acted upon by water. The powdered substanceis mixed and agitated with water, or other convenient fluid; the liquoris allowed to settle for a few moments, and is then decanted off; thecoarsest powder remains at the bottom of the vessel, and the finerpasses over with the liquid. By repeated decantations in this manner,various sediments are obtained of different degrees of fineness; thelast sediment, or that which remains longed suspended in the liquor,being the finest. This process may likewise be used with advantage forseparating substances of different degrees of specific gravity, thoughof the same fineness; this last is chiefly employed in mining, forseparating the heavier metallic ores from the lighter earthy matterswith which they are mixed.
In chemical laboratories, pans and jugs of glass or earthen ware areemployed for this operation; sometimes, for decanting the liquor withoutdisturbing the sediment, the glass syphon ABCHI, Pl. II. Fig. 11. isused, which may be supported by means of the perforated board DE, at theproper depth in the vessel FG, to draw off all the liquor required intothe[Pg 363] receiver LM. The principles and application of this usefulinstrument are so well known as to need no explanation.
A filtre is a species of very fine sieve, which is permeable to theparticles of fluids, but through which the particles of the finestpowdered solids are incapable of passing; hence its use in separatingfine powders from suspension in fluids. In pharmacy, very close and finewoollen cloths are chiefly used for this operation; these are commonlyformed in a conical shape, Pl. II. Fig. 2. which has the advantage ofuniting all the liquor which drains through into a point A, where it maybe readily collected in a narrow mouthed vessel. In large pharmaceuticallaboratories, this filtring bag is streached upon a wooden stand, Pl.II. Fig. 1.
For the purposes of chemistry, as it is requisite to have the filtresperfectly clean, unsized paper is substituted instead of cloth orflannel; through this substance, no solid body, however finely it bepowdered, can penetrate, and fluids percolate through it with thegreatest readiness.[Pg 364] As paper breaks easily when wet, various methods ofsupporting it are used according to circumstances. When a large quantityof fluid is to be filtrated, the paper is supported by the frame ofwood, Pl. II. Fig. 3. ABCD, having a piece of coarse cloth stretchedover it, by means of iron-hooks. This cloth must be well cleaned eachtime it is used, or even new cloth must be employed, if there is reasonto suspect its being impregnated with any thing which can injure thesubsequent operations. In ordinary operations, where moderate quantitiesof fluid are to be filtrated, different kinds of glass funnels are usedfor supporting the paper, as represented Pl. II. Fig. 5. 6. and 7. Whenseveral filtrations must be carried on at once, the board or shelf AB,Fig. 9. supported upon stands C and D, and pierced with round holes, isvery convenient for containing the funnels.
Some liquors are so thick and clammy, as not to be able to penetratethrough paper without some previous preparation, such as clarificationby means of white of eggs, which being mixed with the liquor, coagulateswhen brought to boil, and, entangling the greater part of the impuritiesof the liquor, rises with them to the surface in the state of scum.Spiritous liquors may be clarified in the same manner by means ofisinglass dissolved in water, which coagulates[Pg 365] by the action of thealkohol without the assistance of heat.
As most of the acids are produced by distillation, and are consequentlyclear, we have rarely any occasion to filtrate them; but if, at anytime, concentrated acids require this operation, it is impossible toemploy paper, which would be corroded and destroyed by the acid. Forthis purpose, pounded glass, or rather quartz or rock-cristal, broke inpieces and grossly powdered, answers very well; a few of the largerpieces are put in the neck of the funnel; these are covered with thesmaller pieces, the finer powder is placed over all, and the acid ispoured on at top. For the ordinary purposes of society, river-water isfrequently filtrated by means of clean washed sand, to separate itsimpurities.
This operation is often substituted instead of filtration for separatingsolid particles which are diffused through liquors. These are allowed tosettle in conical vessels, ABCDE, Pl. II. Fig. 10. the diffused mattersgradually subside, and the[Pg 366] clear fluid is gently poured off. If thesediment be extremely light, and apt to mix again with the fluid by theslightest motion, the syphon, Fig. 11. is used, instead of decantation,for drawing off the clear fluid.
In experiments, where the weight of the precipitate must be rigorouslyascertained, decantation is preferable to filtration, providing theprecipitate be several times washed in a considerable proportion ofwater. The weight of the precipitate may indeed be ascertained, bycarefully weighing the filtre before and after the operation; but, whenthe quantity of precipitate is small, the different proportions ofmoisture retained by the paper, in a greater or lesser degree ofexsiccation, may prove a material source of error, which ought carefullyto be guarded against.
I have already shown that there are two methods of dividing theparticles of bodies, themechanical andchemical. The former onlyseparates a solid mass into a great number of smaller masses; and forthese purposes various species of forces are employed, according tocircumstances, such as the strength of man or of animals, the weight ofwater applied through the means of hydraulic engines, the expansivepower of steam, the force of the wind, &c. By all these mechanicalpowers, we can never reduce substances into powder beyond a certaindegree of fineness; and the smallest particle produced in this way,though it seems very minute to our organs, is still in fact a mountain,when compared with the ultimate elementary particles of the pulverizedsubstance.
The chemical agents, on the contrary, divide bodies into their primitiveparticles. If, for instance, a neutral salt be acted upon by these, itis divided, as far as is possible, without ceasing to be a neutral salt.In this Chapter, I mean to[Pg 368] give examples of this kind of division ofbodies, to which I shall add some account of the relative operations.
In chemical language, the terms ofsolution anddissolution havelong been confounded, and have very improperly been indiscriminatelyemployed for expressing both the division of the particles of a salt ina fluid, such as water, and the division of a metal in an acid. A fewreflections upon the effects of these two operations will suffice toshow that they ought not to be confounded together. In the solution ofsalts, the saline particles are only separated from each other, whilstneither the salt nor the water are at all decomposed; we are able torecover both the one and the other in the same quantity as before theoperation. The same thing takes place in the solution of resins inalkohol. During metallic dissolutions, on the contrary, a decomposition,either of the acid, or of the water which dilutes it, always takesplace; the metal combines with oxygen, and is changed into an oxyd, anda gasseous substance is disengaged; so that in reality none of thesubstances[Pg 369] employed remain, after the operation, in the same state theywere in before. This article is entirely confined to the considerationof solution.
To understand properly what takes place during the solution of salts, itis necessary to know, that, in most of these operations, two distincteffects are complicated together, viz. solution by water, and solutionby caloric; and, as the explanation of most of the phenomena of solutiondepends upon the distinction of these two circumstances, I shall enlargea little upon their nature.
Nitrat of potash, usually called nitre or saltpetre, contains verylittle water of cristallization, perhaps even none at all; yet this saltliquifies in a degree of heat very little superior to that of boilingwater. This liquifaction cannot therefore be produced by means of thewater of cristallization, but in consequence of the salt being veryfusible in its nature, and from its passing from the solid to the liquidstate of aggregation, when but a little raised above the temperature ofboiling water. All salts are in this manner susceptible of beingliquified by caloric, but in higher or lower degrees of temperature.Some of these, as the acetites of potash and soda, liquify with a verymoderate heat, whilst others, as sulphat of potash, lime, &c. requirethe strongest fires we are capable of producing. This liquifaction[Pg 370] ofsalts by caloric produces exactly the same phenomena with the melting ofice; it is accomplished in each salt by a determinate degree of heat,which remains invariably the same during the whole time of theliquifaction. Caloric is employed, and becomes fixed during the meltingof the salt, and is, on the contrary, disengaged when the saltcoagulates. These are general phenomena which universally occur duringthe passage of every species of substance from the solid to the fluidstate of aggregation, and from fluid to solid.
These phenomena arising from solution by caloric are always less or moreconjoined with those which take place during solutions in water. Wecannot pour water upon a salt, on purpose to dissolve it, withoutemploying a compound solvent, both water and caloric; hence we maydistinguish several different cases of solution, according to the natureand mode of existence of each salt. If, for instance, a salt bedifficultly soluble in water, and readily so by caloric, it evidentlyfollows, that this salt will be difficultly soluble in cold water, andconsiderably in hot water; such is nitrat of potash, and more especiallyoxygenated muriat of potash. If another salt be little soluble both inwater and caloric, the difference of its solubility in cold and warmwater will be very inconsiderable; sulphat of lime is of this kind. Fromthese considerations,[Pg 371] it follows, that there is a necessary relationbetween the following circumstances; the solubility of a salt in coldwater, its solubility in boiling water, and the degree of temperature atwhich the same salt liquifies by caloric, unassisted by water; and thatthe difference of solubility in hot and cold water is so much greater inproportion to its ready solution in caloric, or in proportion to itssusceptibility of liquifying in a low degree of temperature.
The above is a general view of solution; but, for want of particularfacts, and sufficiently exact experiments, it is still nothing more thanan approximation towards a particular theory. The means of compleatingthis part of chemical science is extremely simple; we have only toascertain how much of each salt is dissolved by a certain quantity ofwater at different degrees of temperature; and as, by the experimentspublished by Mr de la Place and me, the quantity of caloric contained ina pound of water at each degree of the thermometer is accurately known,it will be very easy to determine, by simple experiments, the proportionof water and caloric required for solution by each salt, what quantityof caloric is absorbed by each at the moment of liquifaction, and howmuch is disengaged at the moment of cristallization. Hence the reasonwhy salts are more rapidly soluble in hot than in cold water isperfectly evident. In all solutions[Pg 372] of salts caloric is employed; whenthat is furnished intermediately from the surrounding bodies, it canonly arrive slowly to the salt; whereas this is greatly accelerated whenthe requisite caloric exists ready combined with the water of solution.
In general, the specific gravity of water is augmented by holding saltsin solution; but there are some exceptions to the rule. Some time hence,the quantities of radical, of oxygen, and of base, which constitute eachneutral salt, the quantity of water and caloric necessary for solution,the increased specific gravity communicated to water, and the figure ofthe elementary particles of the cristals, will all be accurately known.From these all the circumstances and phenomena of cristallization willbe explained, and by these means this part of chemistry will becompleated. Mr Seguin has formed the plan of a thorough investigation ofthis kind, which he is extremely capable of executing.
The solution of salts in water requires no particular apparatus; smallglass phials of different sizes, Pl. II. Fig. 16. and 17. pans ofearthern ware, A, Fig. 1. and 2. long-necked matrasses, Fig. 14. andpans or basons of copper or of silver, Fig. 13. and 15. answer very wellfor these operations.[Pg 373]
This is an operation used in chemistry and manufactures for separatingsubstances which are soluble in water from such as are insoluble. Thelarge vat or tub, Pl. II. Fig. 12. having a hole D near its bottom,containing a wooden spiget and fosset or metallic stop-cock DE, isgenerally used for this purpose. A thin stratum of straw is placed atthe bottom of the tub; over this, the substance to be lixiviated is laidand covered by a cloth, then hot or cold water, according to the degreeof solubility of the saline matter, is poured on. When the water issupposed to have dissolved all the saline parts, it is let off by thestop-cock; and, as some of the water charged with salt necessarilyadheres to the straw and insoluble matters, several fresh quantities ofwater are poured on. The straw serves to secure a proper passage for thewater, and may be compared to the straws or glass rods used infiltrating, to keep the paper from touching the sides of the funnel. Thecloth which is laid over the matters under lixiviation prevents thewater from making a hollow in[Pg 374] these substances where it is poured on,through which it might escape without acting upon the whole mass.
This operation is less or more imitated in chemical experiments; but asin these, especially with analytical views, greater exactness isrequired, particular precautions must be employed, so as not to leaveany saline or soluble part in the residuum. More water must be employedthan in ordinary lixiviations, and the substances ought to be previouslystirred up in the water before the clear liquor is drawn off, otherwisethe whole mass might not be equally lixiviated, and some parts mighteven escape altogether from the action of the water. We must likewiseemploy fresh portions of water in considerable quantity, until it comesoff entirely free from salt, which we may ascertain by means of thehydrometer formerly described.
In experiments with small quantities, this operation is convenientlyperformed in jugs or matrasses of glass, and by filtrating the liquorthrough paper in a glass funnel. When the substance is in largerquantity, it may be lixiviated in a kettle of boiling water, andfiltrated through paper supported by cloth in the wooden frame, Pl. II.Fig. 3. and 4.; and in operations in the large way, the tub alreadymentioned must be used.[Pg 375]
This operation is used for separating two substances from each other, ofwhich one at least must be fluid, and whose degrees of volatility areconsiderably different. By this means we obtain a salt, which has beendissolved in water, in its concrete form; the water, by heating, becomescombined with caloric, which renders it volatile, while the particles ofthe salt being brought nearer to each other, and within the sphere oftheir mutual attraction, unite into the solid state.
As it was long thought that the air had great influence upon thequantity of fluid evaporated, it will be proper to point out the errorswhich this opinion has produced. There certainly is a constant slowevaporation from fluids exposed to the free air; and, though thisspecies of evaporation may be considered in some degree as a solution inair, yet caloric has considerable influence in producing it, as isevident from the refrigeration which always accompanies this process;hence we may consider this gradual evaporation as a compound solutionmade partly in[Pg 376] air, and partly in caloric. But the evaporation whichtakes place from a fluid kept continually boiling, is quite different inits nature, and in it the evaporation produced by the action of the airis exceedingly inconsiderable in comparison with that which isoccasioned by caloric. This latter species may be termedvaporizationrather thanevaporation. This process is not accelerated in proportionto the extent of evaporating surface, but in proportion to thequantities of caloric which combine with the fluid. Too free a currentof cold air is often hurtful to this process, as it tends to carry offcaloric from the water, and consequently retards its conversion intovapour. Hence there is no inconvenience produced by covering, in acertain degree, the vessels in which liquids are evaporated by continualboiling, provided the covering body be of such a nature as does notstrongly draw off the caloric, or, to use an expression of DrFranklin's, provided it be a bad conductor of heat. In this case, thevapours escape through such opening as is left, and at least as much isevaporated, frequently more than when free access is allowed to theexternal air.
As during evaporation the fluid carried off by caloric is entirely lost,being sacrificed for the sake of the fixed substances with which it wascombined, this process is only employed where the fluid is of smallvalue, as water, for instance.[Pg 377] But, when the fluid is of moreconsequence, we have recourse to distillation, in which process wepreserve both the fixed substance and the volatile fluid. The vesselsemployed for evaporation are basons or pans of copper, silver, or lead,Pl. II. Fig. 13. and 15. or capsules of glass, porcellain, or stoneware, Pl. II. A, Fig. 1. and 2. Pl. III. Fig. 3 and 4. The best utensilsfor this purpose are made of the bottoms of glass retorts and matrasses,as their equal thinness renders them more fit than any other kind ofglass vessel for bearing a brisk fire and sudden alterations of heat andcold without breaking.
As the method of cutting these glass vessels is no where described inbooks, I shall here give a description of it, that they may be made bychemists for themselves out of spoiled retorts, matrasses, andrecipients, at a much cheaper rate than any which can be procured fromglass manufacturers. The instrument, Pl. III. Fig. 5. consisting of aniron ring AC, fixed to the rod AB, having a wooden handle D, is employedas follows: Make the ring red hot in the fire, and put it upon thematrass G, Fig. 6. which is to be cut; when the glass is sufficientlyheated, throw on a little cold water, and it will generally breakexactly at the circular line heated by the ring.
Small flasks or phials of thin glass are exceeding good vessels forevaporating small quantities[Pg 378] of fluid; they are very cheap, and standthe fire remarkably. One or more of these may be placed upon a secondgrate above the furnace, Pl. III. Fig. 2. where they will onlyexperience a gentle heat. By this means a great number of experimentsmay be carried on at one time. A glass retort, placed in a sand bath,and covered with a dome of baked earth, Pl. III. Fig. 1. answers prettywell for evaporations; but in this way it is always considerably slower,and is even liable to accidents; as the sand heats unequally, and theglass cannot dilate in the same unequal manner, the retort is veryliable to break. Sometimes the sand serves exactly the office of theiron ring formerly mentioned; for, if a single drop of vapour, condensedinto liquid, happens to fall upon the heated part of the vessel, itbreaks circularly at that place. When a very intense fire is necessary,earthen crucibles may be used; but we generally use the wordevaporation to express what is produced by the temperature of boilingwater, or not much higher.[Pg 379]
In this process the integrant parts of a solid body, separated from eachother by the intervention of a fluid, are made to exert the mutualattraction of aggregation, so as to coalesce and reproduce a solid mass.When the particles of a body are only separated by caloric, and thesubstance is thereby retained in the liquid state, all that is necessaryfor making it cristallize, is to remove a part of the caloric which islodged between its particles, or, in other words, to cool it. If thisrefrigeration be slow, and the body be at the same time left at rest,its particles assume a regular arrangement, and cristallization,properly so called, takes place; but, if the refrigeration is maderapidly, or if the liquor be agitated at the moment of its passage tothe concrete state, the cristallization is irregular and confused.
The same phenomena occur with watery solutions, or rather in those madepartly in water, and partly by caloric. So long as there remains asufficiency of water and caloric to keep the particles of the bodyasunder beyond the sphere[Pg 380] of their mutual attraction, the salt remainsin the fluid state; but, whenever either caloric or water is not presentin sufficient quantity, and the attraction of the particles for eachother becomes superior to the power which keeps them asunder, the saltrecovers its concrete form, and the cristals produced are the moreregular in proportion as the evaporation has been slower and moretranquilly performed.
All the phenomena we formerly mentioned as taking place during thesolution of salts, occur in a contrary sense during theircristallization. Caloric is disengaged at the instant of their assumingthe solid state, which furnishes an additional proof of salt being heldin solution by the compound action of water and caloric. Hence, to causesalts to cristallize which readily liquify by means of caloric, it isnot sufficient to carry off the water which held them in solution, butthe caloric united to them must likewise be removed. Nitrat of potash,oxygenated muriat of potash, alum, sulphat of soda, &c. are examples ofthis circumstance, as, to make these salts cristallize, refrigerationmust be added to evaporation. Such salts, on the contrary, as requirelittle caloric for being kept in solution, and which, from thatcircumstance, are nearly equally soluble in cold and warm water, arecristallizable by simply carrying off the water which holds them insolution, and[Pg 381] even recover their solid state in boiling water; such aresulphat of lime, muriat of potash and of soda, and several others.
The art of refining saltpetre depends upon these properties of salts,and upon their different degrees of solubility in hot and cold water.This salt, as produced in the manufactories by the first operation, iscomposed of many different salts; some are deliquescent, and notsusceptible of being cristallized, such as the nitrat and muriat oflime; others are almost equally soluble in hot and cold water, as themuriats of potash and of soda; and, lastly, the saltpetre, or nitrat ofpotash, is greatly more soluble in hot than it is in cold water. Theoperation is begun, by pouring upon this mixture of salts as much wateras will hold even the least soluble, the muriats of soda and of potash,in solution; so long as it is hot, this quantity readily dissolves allthe saltpetre, but, upon cooling, the greater part of this saltcristallizes, leaving about a sixth part remaining dissolved, and mixedwith the nitrat of lime and the two muriats. The nitre obtained by thisprocess is still somewhat impregnated with other salts, because it hasbeen cristallized from water in which these abound: It is completelypurified from these by a second solution in a small quantity of boilingwater, and second cristallization. The water remaining after thesecristallizations of nitre is still loaded with a mixture[Pg 382] of saltpetre,and other salts; by farther evaporation, crude saltpetre, orrough-petre, as the workmen call it, is procured from it, and this ispurified by two fresh solutions and cristallizations.
The deliquescent earthy salts which do not contain the nitric acid arerejected in this manufacture; but those which consist of that acidneutralized by an earthy base are dissolved in water, the earth isprecipitated by means of potash, and allowed to subside; the clearliquor is then decanted, evaporated, and allowed to cristallize. Theabove management for refining saltpetre may serve as a general rule forseparating salts from each other which happen to be mixed together. Thenature of each must be considered, the proportion in which eachdissolves in given quantities of water, and the different solubility ofeach in hot and cold water. If to these we add the property which somesalts possess, of being soluble in alkohol, or in a mixture of alkoholand water, we have many resources for separating salts from each otherby means of cristallization, though it must be allowed that it isextremely difficult to render this separation perfectly complete.
The vessels used for cristallization are pans of earthen ware, A, Pl.II. Fig. 1. and 2. and large flat dishes, Pl. III. Fig. 7. When a salinesolution is to be exposed to a slow evaporation[Pg 383] in the heat of theatmosphere, with free access of air, vessels of some depth, Pl. III.Fig. 3. must be employed, that there may be a considerable body ofliquid; by this means the cristals produced are of considerable size,and remarkably regular in their figure.
Every species of salt cristallizes in a peculiar form, and even eachsalt varies in the form of its cristals according to circumstances,which take place during cristallization. We must not from thenceconclude that the saline particles of each species are indeterminate intheir figures: The primative particles of all bodies, especially ofsalts, are perfectly constant in their specific forms; but the cristalswhich form in our experiments are composed of congeries of minuteparticles, which, though perfectly equal in size and shape, may assumevery dissimilar arrangements, and consequently produce a vast variety ofregular forms, which have not the smallest apparent resemblance to eachother, nor to the original cristal. This subject has been very ablytreated by the Abbé Haüy, in several memoirs presented to the Academy,and in his work upon the structure of cristals: It is only necessary toextend generally to the class of salts the principles he hasparticularly applied to some cristalized stones.[Pg 384]
As distillation has two distinct objects to accomplish, it is divisibleinto simple and compound; and, in this section, I mean to confine myselfentirely to the former. When two bodies, of which one is more volatilethan the other, or has more affinity to caloric, are submitted todistillation, our intention is to separate them from each other: Themore volatile substance assumes the form of gas, and is afterwardscondensed by refrigeration in proper vessels. In this case distillation,like evaporation, becomes a species of mechanical operation, whichseparates two substances from each other without decomposing or alteringthe nature of either. In evaporation, our only object is to preserve thefixed body, without paying any regard to the volatile matter; whereas,in distillation, our principal attention is generally paid to thevolatile substance, unless when we intend to preserve both the one andthe other. Hence, simple distillation is nothing more than evaporationproduced in close vessels.
The most simple distilling vessel is a species of bottle or matrass, A,Pl. III. Fig. 8. which has[Pg 385] been bent from its original form BC to BD,and which is then called a retort; when used, it is placed either in areverberatory furnace, Pl. XIII. Fig. 2. or in a sand bath under a domeof baked earth, Pl. III. Fig. 1. To receive and condense the products,we adapt a recipient, E, Pl. III. Fig. 9. which is luted to the retort.Sometimes, more especially in pharmaceutical operations, the glass orstone ware cucurbit, A, with its capital B, Pl. III. Fig. 12, or theglass alembic and capital, Fig. 13. of one piece, is employed. Thislatter is managed by means of a tubulated opening T, fitted with aground stopper of cristal; the capital, both of the cucurbit andalembic, has a furrow or trench,r r, intended for conveying thecondensed liquor into the beak RS, by which it runs out. As, in almostall distillations, expansive vapours are produced, which might burst thevessels employed, we are under the necessity of having a small hole, T,Fig. 9. in the balloon or recipient, through which these may find vent;hence, in this way of distilling, all the products which are permanentlyaëriform are entirely lost, and even such as difficultly lose that statehave not sufficient space to condense in the balloon: This apparatus isnot, therefore, proper for experiments of investigation, and can only beadmitted in the ordinary operations of the laboratory or in pharmacy. Inthe article appropriated for compound[Pg 386] distillation, I shall explain thevarious methods which have been contrived for preserving the wholeproducts from bodies in this process.
As glass or earthen vessels are very brittle, and do not readily bearsudden alterations of heat and cold, every well regulated laboratoryought to have one or more alembics of metal for distilling water,spiritous liquors, essential oils, &c. This apparatus consists of acucurbit and capital of tinned copper or brass, Pl. III. Fig. 15. and16. which, when judged proper, may be placed in the water bath, D, Fig.17. In distillations, especially of spiritous liquors, the capital mustbe furnished with a refrigetory, SS, Fig. 16. kept continually filledwith cold water; when the water becomes heated, it is let off by thestop-cock, R, and renewed with a fresh supply of cold water. As thefluid distilled is converted into gas by means of caloric furnished bythe fire of the furnace, it is evident that it could not condense, and,consequently, that no distillation, properly speaking, could take place,unless it is made to deposit in the capital all the caloric it receivedin the cucurbit; with this view, the sides of the capital must always bepreserved at a lower temperature than is necessary for keeping thedistilling substance in the state of gas, and the water in therefrigetory is intended for this purpose.[Pg 387] Water is converted into gasby the temperature of 80° (212°), alkohol by 67° (182.75°), ether by 32°(104°); hence these substances cannot be distilled, or, rather, theywill fly off in the state of gas, unless the temperature of therefrigetory be kept under these respective degrees.
In the distillation of spiritous, and other expansive liquors, the abovedescribed refrigetory is not sufficient for condensing all the vapourswhich arise; in this case, therefore, instead of receiving the distilledliquor immediately from the beak, TU, of the capital into a recipient, aworm is interposed between them. This instrument is represented Pl. III.Fig. 18. contained in a worm tub of tinned copper, it consists of ametallic tube bent into a considerable number of spiral revolutions. Thevessel which contains the worm is kept full of cold water, which isrenewed as it grows warm. This contrivance is employed in alldistilleries of spirits, without the intervention of a capital andrefrigetory, properly so called. The one represented in the plate isfurnished with two worms, one of them being particularly appropriated todistillations of odoriferous substances.
In some simple distillations it is necessary to interpose an adopterbetween the retort and receiver, as shown Pl. III. Fig, 11. This may[Pg 388]serve two different purposes, either to separate two products ofdifferent degrees of volatility, or to remove the receiver to a greaterdistance from the furnace, that it may be less heated. But these, andseveral other more complicated instruments of ancient contrivance, arefar from producing the accuracy requisite in modern chemistry, as willbe readily perceived when I come to treat of compound distillation.
This term is applied to the distillation of substances which condense ina concrete or solid form, such as the sublimation of sulphur, and ofmuriat of ammoniac, or sal ammoniac. These operations may beconveniently performed in the ordinary distilling vessels alreadydescribed, though, in the sublimation of sulphur, a species of vessels,named Alludels, have been usually employed. These are vessels of stoneor porcelain ware, which adjust to each other over a cucurbit containingthe sulphur to be sublimed. One of the best subliming vessels, forsubstances which are not very volatile, is a flask,[Pg 389] or phial of glass,sunk about two thirds into a sand bath; but in this way we are apt tolose a part of the products. When these are wished to be entirelypreserved, we must have recourse to the pneumato-chemical distillingapparatus, to be described in the following chapter.
In the preceding chapter, I have only treated of distillation as asimple operation, by which two substances, differing in degrees ofvolatility, may be separated from each other; but distillation oftenactually decomposes the substances submitted to its action, and becomesone of the most complicated operations in chemistry. In everydistillation, the substance distilled must be brought to the state ofgas, in the cucurbit or retort, by combination with caloric: In simpledistillation, this caloric is given out in the refrigeratory or in theworm, and the substance again recovers its liquid or solid form, but thesubstances submitted to compound distillation[Pg 391] are absolutelydecompounded; one part, as for instance the charcoal they contain,remains fixed in the retort, and all the rest of the elements arereduced to gasses of different kinds. Some of these are susceptible ofbeing condensed, and of recovering their solid or liquid forms, whilstothers are permanently aëriform; one part of these are absorbable bywater, some by the alkalies, and others are not susceptible of beingabsorbed at all. An ordinary distilling apparatus, such as has beendescribed in the preceding chapter, is quite insufficient for retainingor for separating these diversified products, and we are obliged to haverecourse, for this purpose, to methods of a more complicated nature.
The apparatus I am about to describe is calculated for the mostcomplicated distillations, and may be simplified according tocircumstances. It consists of a tubulated glass retort A, Pl. IV. Fig.1. having its beak fitted to a tubulated balloon or recipient BC; to theupper orifice D of the balloon a bent tube DEfg is adjusted, which, atits other extremityg, is plunged into the liquor contained in thebottle L, with three necksxxx. Three other similar bottles areconnected with this first one, by means of three similar bent tubesdisposed in the same manner; and the farthest neck of the last bottle isconnected with a jar in a pneumato-chemical apparatus, by means of abent[Pg 392] tube[60]. A determinate weight of distilled water is usually putinto the first bottle, and the other three have each a solution ofcaustic potash in water. The weight of all these bottles, and of thewater and alkaline solution they contain, must be accuratelyascertained. Every thing being thus disposed, the junctures between theretort and recipient, and of the tube D of the latter, must be lutedwith fat lute, covered over with slips of linen, spread with lime andwhite of egg; all the other junctures are to be secured by a lute madeof wax and rosin melted together.
When all these dispositions are completed, and when, by means of heatapplied to the retort A, the substance it contains becomes decomposed,it is evident that the least volatile products must condense or sublimein the beak or neck of the retort itself, where most of the concretesubstances will fix themselves. The more volatile substances, as thelighter oils, ammoniac, and several others, will condense in therecipient GC, whilst the gasses, which are not susceptible ofcondensation by cold, will pass on by the tubes, and boil up through theliquors in the several bottles. Such as are absorbable[Pg 393] by water willremain in the first bottle, and those which caustic alkali can absorbwill remain in the others; whilst such gasses as are not susceptible ofabsorption, either by water or alkalies, will escape by the tube RM, atthe end of which they may be received into jars in a pneumato-chemicalapparatus. The charcoal and fixed earth, &c. which form the substance orresiduum, anciently calledcaput mortuum, remain behind in the retort.
In this manner of operating, we have always a very material proof of theaccuracy of the analysis, as the whole weights of the products takentogether, after the process is finished, must be exactly equal to theweight of the original substance submitted to distillation. Hence, forinstance, if we have operated upon eight ounces of starch or gum arabic,the weight of the charry residuum in the retort, together with that ofall the products gathered in its neck and the balloon, and of all thegas received into the jars by the tube RM added to the additional weightacquired by the bottles, must, when taken together, be exactly eightounces. If the product be less or more, it proceeds from error, and theexperiment must be repeated until a satisfactory result be procured,which ought not to differ more than six or eight grains in the poundfrom the weight of the substance submitted to experiment.[Pg 394]
In experiments of this kind, I for a long time met with an almostinsurmountable difficulty, which must at last have obliged me to desistaltogether, but for a very simple method of avoiding it, pointed out tome by Mr Hassenfratz. The smallest diminution in the heat of thefurnace, and many other circumstances inseparable from this kind ofexperiments, cause frequent reabsorptions of gas; the water in thecistern of the pneumato-chemical apparatus rushes into the last bottlethrough the tube RM, the same circumstance happens from one bottle intoanother, and the fluid is often forced even into the recipient C. Thisaccident is prevented by using bottles having three necks, asrepresented in the plate, into one of which, in each bottle, a capillaryglass-tubeSt,st,st,st, is adapted, so as to have its lowerextremityt immersed in the liquor. If any absorption takes place,either in the retort, or in any of the bottles, a sufficient quantity ofexternal air enters, by means of these tubes, to fill up the void; andwe get rid of the inconvenience at the price of having a small mixtureof common air with the products of the experiment, which is therebyprevented from failing altogether. Though these tubes admit the externalair, they cannot permit any of the gasseous substances to escape, asthey are always shut below by the water of the bottles.[Pg 395]
It is evident that, in the course of experiments with this apparatus,the liquor of the bottles must rise in these tubes in proportion to thepressure sustained by the gas or air contained in the bottles; and thispressure is determined by the height and gravity of the column of fluidcontained in all the subsequent bottles. If we suppose that each bottlecontains three inches of fluid, and that there are three inches of waterin the cistern of the connected apparatus above the orifice of the tubeRM, and allowing the gravity of the fluids to be only equal to that ofwater, it follows that the air in the first bottle must sustain apressure equal to twelve inches of water; the water must therefore risetwelve inches in the tube S, connected with the first bottle, nineinches in that belonging to the second, six inches in the third, andthree in the last; wherefore these tubes must be made somewhat more thantwelve, nine, six, and three inches long respectively, allowance beingmade for oscillatory motions, which often take place in the liquids. Itis sometimes necessary to introduce a similar tube between the retortand recipient; and, as the tube is not immersed in fluid at its lowerextremity, until some has collected in the progress of the distillation,its upper end must be shut at first with a little lute, so as to beopened according to necessity, or after[Pg 396] there is sufficient liquid inthe recipient to secure its lower extremity.
This apparatus cannot be used in very accurate experiments, when thesubstances intended to be operated upon have a very rapid action uponeach other, or when one of them can only be introduced in smallsuccessive portions, as in such as produce violent effervescence whenmixed together. In such cases, we employ a tubulated retort A, Pl. VII.Fig. 1. into which one of the substances is introduced, preferringalways the solid body, if any such is to be treated, we then lute to theopening of the retort a bent tube BCDA, terminating at its upperextremity B in a funnel, and at its other end A in a capillary opening.The fluid material of the experiment is poured into the retort by meansof this funnel, which must be made of such a length, from B to C, thatthe column of liquid introduced may counterbalance the resistanceproduced by the liquors contained in all the bottles, Pl. IV. Fig. 1.
Those who have not been accustomed to use the above described distillingapparatus may perhaps be startled at the great number of openings whichrequire luting, and the time necessary for making all the previouspreparations in experiments of this kind. It is very true that, if wetake into account all the necessary weighings of materials and products,both before and[Pg 397] after the experiments, these preparatory and succeedingsteps require much more time and attention than the experiment itself.But, when the experiment succeeds properly, we are well rewarded for allthe time and trouble bestowed, as by one process carried on in thisaccurate manner much more just and extensive knowledge is acquired ofthe nature of the vegetable or animal substance thus submitted toinvestigation, than by many weeks assiduous labour in the ordinarymethod of proceeding.
When in want of bottles with three orifices, those with two may be used;it is even possible to introduce all the three tubes at one opening, soas to employ ordinary wide-mouthed bottles, provided the opening besufficiently large. In this case we must carefully fit the bottles withcorks very accurately cut, and boiled in a mixture of oil, wax, andturpentine. These corks are pierced with the necessary holes forreceiving the tubes by means of a round file, as in Pl. IV. Fig. 8.[Pg 398]
I have already pointed out the difference between solution of salts inwater and metallic dissolutions. The former requires no particularvessels, whereas the latter requires very complicated vessels of lateinvention, that we may not lose any of the products of the experiment,and may thereby procure truly conclusive results of the phenomena whichoccur. The metals, in general, dissolve in acids with effervescence,which is only a motion excited in the solvent by the disengagement of agreat number of bubbles of air or aëriform fluid, which proceed from thesurface of the metal, and break at the surface of the liquid.
Mr Cavendish and Dr Priestley were the first inventors of a properapparatus for collecting these elastic fluids. That of Dr Priestley isextremely simple, and consists of a bottle A, Pl. VII. Fig. 2. with itscork B, through which passes the bent glass tube BC, which is engagedunder a jar filled with water in the pneumato-chemical apparatus, orsimply in a bason full of water. The metal is first introduced into the[Pg 399]bottle, the acid is then poured over it, and the bottle is instantlyclosed with its cork and tube, as represented in the plate. But thisapparatus has its inconveniencies. When the acid is much concentrated,or the metal much divided, the effervescence begins before we have timeto cork the bottle properly, and some gas escapes, by which we areprevented from ascertaining the quantity disengaged with rigorousexactness. In the next place, when we are obliged to employ heat, orwhen heat is produced by the process, a part of the acid distills, andmixes with the water of the pneumato-chemical apparatus, by which meanswe are deceived in our calculation of the quantity of acid decomposed.Besides these, the water in the cistern of the apparatus absorbs all thegas produced which is susceptible of absorption, and renders itimpossible to collect these without loss.
To remedy these inconveniencies, I at first used a bottle with twonecks, Pl. VII. Fig. 3. into one of which the glass funnel BC is lutedso as to prevent any air escaping; a glass rod DE is fitted with emeryto the funnel, so as to serve the purpose of a stopper. When it is used,the matter to be dissolved is first introduced into the bottle, and theacid is then permitted to pass in as slowly as we please, by raising theglass rod gently as often as is necessary until saturation is produced.[Pg 400]
Another method has been since employed, which serves the same purpose,and is preferable to the last described in some instances. This consistsin adapting to one of the mouths of the bottle A, Pl. VII. Fig. 4. abent tube DEFG, having a capillary opening at D, and ending in a funnelat G. This tube is securely luted to the mouth C of the bottle. When anyliquid is poured into the funnel, it falls down to F; and, if asufficient quantity be added, it passes by the curvature E, and fallsslowly into the bottle, so long as fresh liquor is supplied at thefunnel. The liquor can never be forced out of the tube, and no gas canescape through it, because the weight of the liquid serves the purposeof an accurate cork.
To prevent any distillation of acid, especially in dissolutionsaccompanied with heat, this tube is adapted to the retort A, Pl. VII.Fig. 1. and a small tubulated recipient, M, is applied, in which anyliquor which may distill is condensed. On purpose to separate any gasthat is absorbable by water, we add the double necked bottle L, halffilled with a solution of caustic potash; the alkali absorbs anycarbonic acid gas, and usually only one or two other gasses pass intothe jar of the connected pneumato-chemical apparatus through the tubeNO. In the first chapter of this third part we have directed how theseare to be separated and examined.[Pg 401] If one bottle of alkaline solution benot thought sufficient, two, three, or more, may be added.
For these operations a peculiar apparatus, especially intended for thiskind of experiment, is requisite. The one I am about to describe isfinally adopted, as the best calculated for the purpose, after numerouscorrections and improvements. It consists of a large matrass, A, Pl. X.fig. 1. holding about twelve pints, with a cap of brassa b, stronglycemented to its mouth, and into which is screwed a bent tubec d,furnished with a stop-cocke. To this tube is joined the glassrecipient B, having three openings, one of which communicates with thebottle C, placed below it. To the posterior opening of this recipient isfitted a glass tubeg h i, cemented atg andi to collets ofbrass, and intended to contain a very deliquescent concrete neutralsalt, such as nitrat or muriat of lime, acetite of potash, &c. This tubecommunicates with two bottles D and E, filled tox andy with asolution of caustic potash.[Pg 402]
All the parts of this machine are joined together by accurate screws,and the touching parts have greased leather interposed, to prevent anypassage of air. Each piece is likewise furnished with two stop-cocks, bywhich its two extremities may be closed, so that we can weigh eachseparately at any period of the operation.
The fermentable matter, such as sugar, with a proper quantity of yeast,and diluted with water, is put into the matrass. Sometimes, when thefermentation is too rapid, a considerable quantity of froth is produced,which not only fills the neck of the matrass, but passes into therecipient, and from thence runs down into the bottle C. On purpose tocollect this scum and must, and to prevent it from reaching the tubefilled with deliquescent salts, the recipient and connected bottle aremade of considerable capacity.
In the vinous fermentation, only carbonic acid gas is disengaged,carrying with it a small proportion of water in solution. A great partof this water is deposited in passing through the tubeg h i, which isfilled with a deliquescent salt in gross powder, and the quantity isascertained by the augmentation of the weight of the salt. The carbonicacid gas bubbles up through the alkaline solution in the bottle D, towhich it is conveyed by the tubek l m. Any small portion which maynot be absorbed by this[Pg 403] first bottle is secured by the solution in thesecond bottle E, so that nothing, in general, passes into the jar F,except the common air contained in the vessels at the commencement ofthe experiment.
The same apparatus answers extremely well for experiments upon theputrefactive fermentation; but, in this case, a considerable quantity ofhydrogen gas is disengaged through the tubeq r s t u, by which it isconveyed into the jar F; and, as this disengagement is very rapid,especially in summer, the jar must be frequently changed. Theseputrefactive fermentations require constant attendance from the abovecircumstance, whereas the vinous fermentation hardly needs any. By meansof this apparatus we can ascertain, with great precision, the weights ofthe substances submitted to fermentation, and of the liquid and aëriformproducts which are disengaged. What has been already said in Part I.Chap. XIII. upon the products of the vinous fermentation, may beconsulted.[Pg 404]
Having already given an account, in the first part of this work, of theexperiments relative to the decomposition of water, I shall avoid anyunnecessary repetitions, and only give a few summary observations uponthe subject in this section. The principal substances which have thepower of decomposing water are iron and charcoal; for which purpose,they require to be made red hot, otherwise the water is only reducedinto vapours, and condenses afterwards by refrigeration, withoutsustaining the smallest alteration. In a red heat, on the contrary, ironor charcoal carry off the oxygen from its union with hydrogen; in thefirst case, black oxyd of iron is produced, and the hydrogen isdisengaged pure in form of gas; in the other case, carbonic acid gas isformed, which disengages, mixed with the hydrogen gas; and this latteris commonly carbonated, or holds charcoal in solution.
A musket barrel, without its breach pin, answers exceedingly well forthe decomposition of water, by means of iron, and one should be[Pg 405] chosenof considerable length, and pretty strong. When too short, so as to runthe risk of heating the lute too much, a tube of copper is to bestrongly soldered to one end. The barrel is placed in a long furnace,CDEF, Pl. VII. Fig. 11. so as to have a few degrees of inclination fromE to F; a glass retort A, is luted to the upper extremity E, whichcontains water, and is placed upon the furnace VVXX. The lower extremityF is luted to a worm SS, which is connected with the tubulated bottle H,in which any water distilled without decomposition, during theoperation, collects, and the disengaged gas is carried by the tube KK tojars in a pneumato-chemical apparatus. Instead of the retort a funnelmay be employed, having its lower part shut by a stop-cock, throughwhich the water is allowed to drop gradually into the gun-barrel.Immediately upon getting into contact with the heated part of the iron,the water is converted into steam, and the experiment proceeds in thesame manner as if it were furnished in vapours from the retort.
In the experiment made by Mr Meusnier and me before a committee of theAcademy, we used every precaution to obtain the greatest possibleprecision in the result of our experiment, having even exhausted all thevessels employed before we began, so that the hydrogen gas obtainedmight be free from any mixture[Pg 406] of azotic gas. The results of thatexperiment will hereafter be given at large in a particular memoir.
In numerous experiments, we are obliged to use tubes of glass,porcelain, or copper, instead of gun-barrels; but glass has thedisadvantage of being easily melted and flattened, if the heat be in thesmallest degree raised too high; and porcelain is mostly full of smallminute pores, through which the gas escapes, especially when compressedby a column of water. For these reasons I procured a tube of brass,which Mr de la Briche got cast and bored out of the solid for me atStrasburg, under his own inspection. This tube is extremely convenientfor decomposing alkohol, which resolves into charcoal, carbonic acidgas, and hydrogen gas; it may likewise be used with the same advantagefor decomposing water by means of charcoal, and in a great number ofexperiments of this nature.[Pg 407]
[60] The representation of this apparatus, Pl. IV. Fig. 1. willconvey a much better idea of its disposition than can possibly be givenby the most laboured description.—E.
The necessity of properly securing the junctures of chemical vessels toprevent the escape of any of the products of experiments, must besufficiently apparent; for this purpose lutes are employed, which oughtto be of such a nature as to be equally impenetrable to the most subtilesubstances, as glass itself, through which only caloric can escape.
This first object of lutes is very well accomplished by bees wax, meltedwith about an eighth part of turpentine. This lute is very easilymanaged, sticks very closely to glass, and is very difficultlypenetrable; it may be rendered more consistent, and less or more hard orpliable, by adding different kinds of resinous matters. Though thisspecies of lute answers extremely well for retaining gasses and vapours,there are many chemical experiments which produce considerable heat, bywhich this lute becomes liquified, and consequently the expansivevapours must very readily force through and escape.[Pg 408]
For such cases, the following fat lute is the best hitherto discovered,though not without its disadvantages, which shall be pointed out. Takevery pure and dry unbaked clay, reduced to a very fine powder, put thisinto a brass mortar, and beat it for several hours with a heavy ironpestle, dropping in slowly some boiled lintseed oil; this is oil whichhas been oxygenated, and has acquired a drying quality, by being boiledwith litharge. This lute is more tenacious, and applies better, if ambervarnish be used instead of the above oil. To make this varnish, meltsome yellow amber in an iron laddle, by which operation it loses a partof its succinic acid, and essential oil, and mix it with lintseed oil.Though the lute prepared with this varnish is better than that made withboiled oil, yet, as its additional expence is hardly compensated by itssuperior quality, it is seldom used.
The above fat lute is capable of sustaining a very violent degree ofheat, is impenetrable by acids and spiritous liquors, and adheresexceedingly well to metals, stone ware, or glass, providing they havebeen previously rendered perfectly dry. But if, unfortunately, any ofthe liquor in the course of an experiment gets through, either betweenthe glass and the lute, or between the layers of the lute itself, so asto moisten the part, it is extremely difficult to close[Pg 409] the opening.This is the chief inconvenience which attends the use of fat lute, andperhaps the only one it is subject to. As it is apt to soften by heat,we must surround all the junctures with slips of wet bladder appliedover the luting, and fixed on by pack-thread tied round both above andbelow the joint; the bladder, and consequently the lute below, must befarther secured by a number of turns of pack-thread all over it. Bythese precautions, we are free from every danger of accident; and thejunctures secured in this manner may be considered, in experiments, ashermetically sealed.
It frequently happens that the figure of the junctures prevents theapplication of ligatures, which is the case with the three-neckedbottles formerly described; and it even requires great address to applythe twine without shaking the apparatus; so that, where a number ofjunctures require luting, we are apt to displace several while securingone. In these cases, we may substitute slips of linen, spread with whiteof egg and lime mixed together, instead of the wet bladder. These areapplied while still moist, and very speedily dry and acquireconsiderable hardness. Strong glue dissolved in water may answer insteadof white of egg. These fillets are usefully applied likewise overjunctures luted together with wax and rosin.[Pg 410]
Before applying a lute, all the junctures of the vessels must beaccurately and firmly fitted to each other, so as not to admit of beingmoved. If the beak of a retort is to be luted to the neck of arecipient, they ought to fit pretty accurately; otherwise we must fixthem, by introducing short pieces of soft wood or of cork. If thedisproportion between the two be very considerable, we must employ acork which fits the neck of the recipient, having a circular hole ofproper dimensions to admit the beak of the retort. The same precautionis necessary in adapting bent tubes to the necks of bottles in theapparatus represented Pl. IV. Fig. 1. and others of a similar nature.Each mouth of each bottle must be fitted with a cork, having a hole madewith a round file of a proper size for containing the tube. And, whenone mouth is intended to admit two or more tubes, which frequentlyhappens when we have not a sufficient number of bottles with two orthree necks, we must use a cork with two or three holes, Pl. IV. Fig. 8.
When the whole apparatus is thus solidly joined, so that no part canplay upon another, we begin to lute. The lute is softened by kneadingand rolling it between the fingers, with the assistance of heat, ifnecessary. It is rolled into little cylindrical pieces, and applied tothe junctures, taking great care to make it[Pg 411] apply close, and adherefirmly, in every part; a second roll is applied over the first, so as topass it on each side, and so on till each juncture be sufficientlycovered; after this, the slips of bladder, or of linen, as abovedirected, must be carefully applied over all. Though this operation mayappear extremely simple, yet it requires peculiar delicacy andmanagement; great care must be taken not to disturb one juncture whilstluting another, and more especially when applying the fillets andligatures.
Before beginning any experiment, the closeness of the luting oughtalways to be previously tried, either by slightly heating the retort A,Pl. IV. Fig. 1, or by blowing in a little air by some of theperpendicular tubesS s s s; the alteration of pressure causes achange in the level of the liquid in these tubes. If the apparatus beaccurately luted, this alteration of level will be permanent; whereas,if there be the smallest, opening in any of the junctures, the liquidwill very soon recover its former level. It must always be remembered,that the whole success of experiments in modern chemistry depends uponthe exactness of this operation, which therefore requires the utmostpatience, and most attentive accuracy.
It would be of infinite service to enable chemists, especially those whoare engaged in pneumatic processes, to dispense with the use of lutes,[Pg 412]or at least to diminish the number necessary in complicated instruments.I once thought of having my apparatus constructed so as to unite in allits parts by fitting with emery, in the way of bottles with cristalstoppers; but the execution of this plan was extremely difficult. I havesince thought it preferable to substitute columns of a few lines ofmercury in place of lutes, and have got an apparatus constructed uponthis principle, which appears capable of very convenient application ina great number of circumstances.
It consists of a double necked bottle A, Pl. XII. Fig. 12.; the interiorneckbc communicates with the inside of the bottle, and the exteriorneck or rimde leaves an interval between the two necks, forming adeep gutter intended to contain the mercury. The cap or lid of glass Benters this gutter, and is properly fitted to it, having notches in itslower edge for the passage of the tubes which convey the gas. Thesetubes, instead of entering directly into the bottles as in the ordinaryapparatus, have a double bend for making them enter the gutter, asrepresented in Fig. 13. and for making them fit the notches of the capB; they rise again from the gutter to enter the inside of the bottleover the border of the inner mouth. When the tubes are disposed in theirproper places, and the cap firmly fitted on, the gutter is filled with[Pg 413]mercury, by which means the bottle is completely excluded from anycommunication, excepting through the tubes. This apparatus may be veryconvenient in many operations in which the substances employed have noaction upon Mercury. Pl. XII. Fig. 14. represents an apparatus upon thisprinciple properly fitted together.
Mr Seguin, to whose active and intelligent assistance I have been veryfrequently much indebted, has bespoken for me, at the glass-houses, someretorts hermetically united to their recipients, by which luting will bealtogether unnecessary.
Combustion, according to what has been already said in the First Part ofthis Work, is the decomposition of oxygen gas produced by a combustiblebody. The oxygen which forms the base of this gas is absorbed by, andenters into, combination with the burning body, while the caloric andlight are set free. Every combustion, therefore, necessarily supposesoxygenation; whereas, on the contrary, every oxygenation does notnecessarily imply concomitant combustion; because combustion, properlyso called, cannot take place without disengagement of caloric and light.Before combustion can take place, it is necessary that the base ofoxygen gas should have greater affinity to the combustible body than ithas to caloric;[Pg 415] and this elective attraction, to use Bergman'sexpression, can only take place at a certain degree of temperature,which is different for each combustible substance; hence the necessityof giving a first motion or beginning to every combustion by theapproach of a heated body. This necessity of heating any body we mean toburn depends upon certain considerations, which have not hitherto beenattended to by any natural philosopher, for which reason I shall enlargea little upon the subject in this place.
Nature is at present in a state of equilibrium, which cannot have beenattained until all the spontaneous combustions or oxygenations possiblein the ordinary degrees of temperature had taken place. Hence, no newcombustions or oxygenations can happen without destroying thisequilibrium, and raising the combustible substances to a superior degreeof temperature. To illustrate this abstract view of the matter byexample: Let us suppose the usual temperature of the earth a littlechanged, and that it is raised only to the degree of boiling water; itis evident, that, in this case, phosphorus, which is combustible in aconsiderably lower degree of temperature, would no longer exist innature in its pure and simple state, but would always be procured in itsacid or oxygenated state, and its radical would become one of thesubstances unknown[Pg 416] to chemistry. By gradually increasing thetemperature of the earth the same circumstance would successively happento all the bodies capable of combustion; and, at last, every possiblecombustion having taken place, there would no longer exist anycombustible body whatever, as every substance susceptible of thatoperation would be oxygenated, and consequently incombustible.
There cannot therefore exist, so far as relates to us, any combustiblebody, except such as are incombustible in the ordinary temperatures ofthe earth; or, what is the same thing, in other words, that it isessential to the nature of every combustible body not to possess theproperty of combustion, unless heated, or raised to the degree oftemperature at which its combustion naturally takes place. When thisdegree is once produced, combustion commences, and the caloric which isdisengaged by the decomposition of the oxygen gas keeps up thetemperature necessary for continuing combustion. When this is not thecase, that is, when the disengaged caloric is insufficient for keepingup the necessary temperature, the combustion ceases: This circumstanceis expressed in common language by saying, that a body burns ill, orwith difficulty.
Although combustion possesses some circumstances in common withdistillation, especially[Pg 417] with the compound kind of that operation, theydiffer in a very material point. In distillation there is a separationof one part of the elements of the substance from each other, and acombination of these, in a new order, occasioned by the affinities whichtake place in the increased temperature produced during distillation:This likewise happens in combustion, but with this farther circumstance,that a new element, not originally in the body, is brought into action;oxygen is added to the substance submitted to the operation, and caloricis disengaged.
The necessity of employing oxygen in the state of gas in all experimentswith combustion, and the rigorous determination of the quantitiesemployed, render this kind of operations peculiarly troublesome. Asalmost all the products of combustion are disengaged in the state ofgas, it is still more difficult to retain them than even those furnishedduring compound distillation; hence this precaution was entirelyneglected by the ancient chemists; and this set of experimentsexclusively belong to modern chemistry.
Having thus pointed out, in a general way, the objects to be had in viewin experiments upon combustion, I proceed, in the following sections ofthis chapter, to describe the different instruments I have used withthis view. The following arrangement is formed, not upon the[Pg 418] nature ofthe combustible bodies, but upon that of the instruments necessary forcombustion.
In these combustions we begin by filling a jar, capable at least ofholding six pints, with oxygen gas in the water apparatus, Pl. V. Fig.1.; when it is perfectly full, so that the gas begins to flow out below,the jar, A, is carried to the mercury apparatus, Pl. IV. Fig. 3. We thendry the surface of the mercury, both within and without the jar, bymeans of blotting-paper, taking care to keep the paper for some timeentirely immersed in the mercury before it is introduced under the jar,lest we let in any common air, which sticks very obstinately to thesurface of the paper. The body to be submitted to combustion, beingfirst very accurately weighed in nice scales, is placed in a small flatshallow dish, D, of iron or porcelain; this is covered by the larger cupP, which serves the office of a diving bell, and the whole is passedthrough the mercury into the jar, after which the larger cup is retired.The difficulty of passing the materials of combustion in this manner[Pg 419]through the mercury may be avoided by raising one of the sides of thejar, A, for a moment, and slipping in the little cup, D, with thecombustible body as quickly as possible. In this manner of operating, asmall quantity of common air gets into the jar, but it is so veryinconsiderable as not to injure either the progress or accuracy of theexperiment in any sensible degree.
When the cup, D, is introduced under the jar, we suck out a part of theoxygen gas, so as to raise the mercury to EF, as formerly directed, PartI. Chap. V. otherwise, when the combustible body is set on fire, the gasbecoming dilated would be in part forced out, and we should no longer beable to make any accurate calculation of the quantities before and afterthe experiment. A very convenient mode of drawing out the air is bymeans of an air-pump syringe adapted to the syphon, GHI, by which themercury may be raised to any degree under twenty-eight inches. Veryinflammable bodies, as phosphorus, are set on fire by means of thecrooked iron wire, MN, Pl. IV. Fig. 16. made red hot, and passed quicklythrough the mercury. Such as are less easily set on fire have a smallportion of tinder, upon which a minute particle of phosphorus is fixed,laid upon them before using the red hot iron.[Pg 420]
In the first moment of combustion the air, being heated, rarifies, andthe mercury descends; but when, as in combustions of phosphorus andiron, no elastic fluid is formed, absorption becomes presently verysensible, and the mercury rises high into the jar. Great attention mustbe used not to burn too large a quantity of any substance in a givenquantity of gas, otherwise, towards the end of the experiment, the cupwould approach so near the top of the jar as to endanger breaking it bythe great heat produced, and the sudden refrigeration from the coldmercury. For the methods of measuring the volume of the gasses, and forcorrecting the measures according to the heighth of the barometer andthermometer, &c. see Chap. II. Sect. V. and VI. of this part.
The above process answers very well for burning all the concretesubstances, and even for the fixed oils: These last are burnt in lampsunder the jar, and are readily set on fire by means of tinder,phosphorus, and hot iron. But it is dangerous for substances susceptibleof evaporating in a moderate heat, such as ether, alkohol, and theessential oils; these substances dissolve in considerable quantity inoxygen gas; and, when set on fire, a dangerous and sudden explosiontakes place, which carries up the jar to a great height, and dashes itin a thousand pieces. From two such explosions some of the[Pg 421] members ofthe Academy and myself escaped very narrowly. Besides, though thismanner of operating is sufficient for determining pretty accurately thequantity of oxygen gas absorbed, and of carbonic acid produced, as wateris likewise formed in all experiments upon vegetable and animal matterswhich contain an excess of hydrogen, this apparatus can neither collectit nor determine its quantity. The experiment with phosphorus is evenincomplete in this way, as it is impossible to demonstrate that theweight of the phosphoric acid produced is equal to the sum of theweights of the phosphorus burnt and oxygen gas absorbed during theprocess. I have been therefore obliged to vary the instruments accordingto circumstances, and to employ several of different kinds, which Ishall describe in their order, beginning with that used for burningphosphorus.
Take a large balloon, A, Pl. IV. Fig. 4. of cristal or white glass, withan opening, EF, about two inches and a half, or three inches, diameter,to which a cap of brass is accurately fitted with emery, and which hastwo holes for the passage of the tubesxxx,yyy. Before shutting theballoon with its cover, place within it the stand, BC, supporting thecup of porcelain, D, which contains the phosphorus. Then lute on the capwith fat lute, and allow it to dry for some days, and weigh the wholeaccurately;[Pg 422] after this exhaust the balloon by means of an air-pumpconnected with the tubexxx, and fill it with oxygen gas by the tubeyyy, from the gazometer, Pl. VIII. Fig. 1. described Chap. II. SectII. of this part. The phosphorus is then set on fire by means of aburning-glass, and is allowed to burn till the cloud of concretephosphoric acid stops the combustion, oxygen gas being continuallysupplied from the gazometer. When the apparatus has cooled, it isweighed and unluted; the tare of the instrument being allowed, theweight is that of the phosphoric acid contained. It is proper, forgreater accuracy, to examine the air or gas contained in the balloonafter combustion, as it may happen to be somewhat heavier or lighterthan common air; and this difference of weight must be taken intoaccount in the calculations upon the results of the experiment.
The apparatus I have employed for this process consists of a smallconical furnace of hammered copper, represented in perspective, Pl. XII.Fig. 9. and internally displayed Fig. 11. It is[Pg 423] divided into thefurnace, ABC, where the charcoal is burnt, the grate,d e, and theash-hole, F; the tube, GH, in the middle of the dome of the furnaceserves to introduce the charcoal, and as a chimney for carrying off theair which has served for combustion. Through the tube,l m n, whichcommunicates with the gazometer, the hydrogen gas, or air, intended forsupporting the combustion, is conveyed into the ash-hole, F, whence itis forced, by the application of pressure to the gazometer, to passthrough the grate,d e, and to blow upon the burning charcoal placedimmediately above.
Oxygen gas, which forms 28/100 of atmospheric air, is changed intocarbonic acid gas during combustion with charcoal, whilst the azotic gasof the air is not altered at all. Hence, after the combustion ofcharcoal in atmospheric air, a mixture of carbonic acid gas and azoticgas must remain; to allow this mixture to pass off, the tube,o p, isadapted to the chimney, GH, by means of a screw at G, and conveys thegas into bottles half filled with solution of caustic potash. Thecarbonic acid gas is absorbed by the alkali, and the azotic gas isconveyed into a second gazometer, where its quantity is ascertained.
The weight of the furnace, ABC, is first accurately determined, thenintroduce the tube RS, of known weight, by the chimney, GH,[Pg 424] till itslower end S, rests upon the grate,d e, which it occupies entirely; inthe next place, fill the furnace with charcoal, and weigh the wholeagain, to know the exact quantity of charcoal submitted to experiment.The furnace is now put in its place, the tube,l m n, is screwed tothat which communicates with the gazometer, and the tube,o p, to thatwhich communicates with the bottles of alkaline solution. Every thingbeing in readiness, the stop-cock of the gazometer is opened, a smallpiece of burning charcoal is thrown into the tube, RS, which isinstantly withdrawn, and the tube,o p, is screwed to the chimney, GH.The little piece of charcoal falls upon the grate, and in this mannergets below the whole charcoal, and is kept on fire by the stream of airfrom the gazometer. To be certain that the combustion is begun, and goeson properly, the tube,q r s, is fixed to the furnace, having a pieceof glass cemented to its upper extremity,s, through which we can seeif the charcoal be on fire.
I neglected to observe above, that the furnace, and its appendages, areplunged in water in the cistern, TVXY, Fig. 11. Pl. XII. to which icemay be added to moderate the heat, if necessary; though the heat is byno means very considerable, as there is no air but what comes from thegazometer, and no more of the charcoal[Pg 425] burns at one time than what isimmediately over the grate.
As one piece of charcoal is consumed another falls down into its place,in consequence of the declivity of the sides of the furnace; this getsinto the stream of air from the grate,d e, and is burnt; and so on,successively, till the whole charcoal is consumed. The air which hasserved the purpose of the combustion passes through the mass ofcharcoal, and is forced by the pressure of the gazometer to escapethrough the tube,o p, and to pass through the bottles of alkalinesolution.
This experiment furnishes all the necessary data for a complete analysisof atmospheric air and of charcoal. We know the weight of charcoalconsumed; the gazometer gives us the measure of the air employed; thequantity and quality of gas remaining after combustion may bedetermined, as it is received, either in another gazometer, or in jars,in a pneumato-chemical apparatus; the weight of ashes remaining in theash-hole is readily ascertained; and, finally, the additional weightacquired by the bottles of alkaline solution gives the exact quantity ofcarbonic acid formed during the process. By this experiment we maylikewise determine, with sufficient accuracy, the proportions in whichcharcoal and oxygen enter into the composition of carbonic acid.[Pg 426]
In a future memoir I shall give an account to the Academy of a series ofexperiments I have undertaken, with this instrument, upon all thevegetable and animal charcoals. By some very slight alterations, thismachine may be made to answer for observing the principal phenomena ofrespiration.
Oils are more compound in their nature than charcoal, being formed bythe combination of at least two elements, charcoal and hydrogen; ofcourse, after their combustion in common air, water, carbonic acid gas,and azotic gas, remain. Hence the apparatus employed for theircombustion requires to be adapted for collecting these three products,and is consequently more complicated than the charcoal furnace.
The apparatus I employ for this purpose is composed of a large jar orpitcher A, Pl. XII. Fig. 4. surrounded at its upper edge by a rim ofiron properly cemented at DE, and receding from the jar at BC, so as toleave a furrow or gutterxx, between it and the outside of the jar,[Pg 427]somewhat more than two inches deep. The cover or lid of the jar, Fig. 5.is likewise surrounded by an iron rimf g, which adjusts into thegutterxx, Fig. 4. which being filled with mercury, has the effect ofclosing the jar hermetically in an instant, without using any lute; and,as the gutter will hold about two inches of mercury, the air in the jarmay be made to sustain the pressure of more than two feet of water,without danger of its escaping.
The lid has four holes, Thik, for the passage of an equalnumber of tubes. The opening T is furnished with a leather box, throughwhich passes the rod, Fig. 3. intended for raising and lowering the wickof the lamp, as will be afterwards directed. The three other holes areintended for the passage of three several tubes, one of which conveysthe oil to the lamp, a second conveys air for keeping up the combustion,and the third carries off the air, after it has served for combustion.The lamp in which the oil is burnt is represented Fig. 2;a is thereservoir of oil, having a funnel by which it is filled;b c d e f g his a syphon which conveys the oil to the lamp 11; 7, 8, 9, 10, is thetube which conveys the air for combustion from the gazometer to the samelamp. The tubeb c is formed externally, at its lower endb, into amale screw, which turns in a female screw in the lid of the reservoir ofoila; so that, by turning[Pg 428] the reservoir one way or the other, it ismade to rise or fall, by which the oil is kept at the necessary level.
When the syphon is to be filled, and the communication formed betweenthe reservoir of oil and the lamp, the stop-cockc is shut, and thatate opened, oil is poured in by the openingf at the top of thesyphon, till it rises within three or four lines of the upper edge ofthe lamp, the stop-cockk is then shut, and that atc opened; theoil is then poured in atf, till the branchb c d of the syphon isfilled, and then the stop-cocke is closed. The two branches of thesyphon being now completely filled, a communication is fully establishedbetween the reservoir and the lamp.
In Pl. XII. Fig. 1. all the parts of the lamp 11, Fig. 2. arerepresented magnified, to show them distinctly. The tubei k carriesthe oil from the reservoir to the cavitya a a a, which contains thewick; the tube 9, 10, brings the air from the gazometer for keeping upthe combustion; this air spreads through the cavityd d d d, and, bymeans of the passagesc c c c andb b b b, is distributed on eachside of the wick, after the principles of the lamps constructed byArgand, Quinquet, and Lange.
To render the whole of this complicated apparatus more easilyunderstood, and that its description may make all others of the samekind[Pg 429] more readily followed, it is represented, completely connectedtogether for use, in Pl. XI. The gazometer P furnishes air for thecombustion by the tube and stop-cock 1, 2; the tube 2, 3, communicateswith a second gazometer, which is filled whilst the first one isemptying during the process, that there may be no interruption to thecombustion; 4, 5, is a tube of glass filled with deliquescent salts, fordrying the air as much as possible in its passage; and the weight ofthis tube and its contained salts, at the beginning of the experiment,being known, it is easy to determine the quantity of water absorbed bythem from the air. From this deliquescent tube the air is conductedthrough the pipe 5, 6, 7, 8, 9, 10, to the lamp 11, where it spreads onboth sides of the wick, as before described, and feeds the flame. Onepart of this air, which serves to keep up the combustion of the oil,forms carbonic acid gas and water, by oxygenating its elements. Part ofthis water condenses upon the sides of the pitcher A, and another partis held in solution in the air by means of caloric furnished by thecombustion. This air is forced by the compression of the gazometer topass through the tube 12, 13, 14, 15, into the bottle 16, and the worm17, 18, where the water is fully condensed from the refrigeration of theair; and, if any water still remains[Pg 430] in solution, it is absorbed bydeliquescent salts contained in the tube 19, 20.
All these precautions are solely intended for collecting and determiningthe quantity of water formed during the experiment; the carbonic acidand azotic gas remains to be ascertained. The former is absorbed bycaustic alkaline solution in the bottles 22 and 25. I have onlyrepresented two of these in the figure, but nine at least are requisite;and the last of the series may be half filled with lime-water, which isthe most certain reagent for indicating the presence of carbonic acid;if the lime-water is not rendered turbid, we may be certain that nosensible quantity of that acid remains in the air.
The rest of the air which has served for combustion, and which chieflyconsists of azotic gas, though still mixed with a considerable portionof oxygen gas, which has escaped unchanged from the combustion, iscarried through a third tube 28, 29, of deliquescent salts, to depriveit of any moisture it may have acquired in the bottles of alkalinesolution and lime-water, and from thence by the tube 29, 30, into agazometer, where its quantity is ascertained. Small essays are thentaken from it, which are exposed to a solution of sulphuret of potash,to ascertain the proportions of oxygen and azotic gas it contains.[Pg 431]
In the combustion of oils the wick becomes charred at last, andobstructs the rise of the oil; besides, if we raise the wick above acertain height, more oil rises through its capillary tubes than thestream of air is capable of consuming, and smoke is produced. Hence itis necessary to be able to lengthen or shorten the wick without openingthe apparatus; this is accomplished by means of the rod 31, 32, 33, 34,which passes through a leather-box, and is connected with the support ofthe wick; and that the motion of this rod, and consequently of the wick,may be regulated with the utmost smoothness and facility; it is moved atpleasure by a pinnion which plays in a toothed rack. The rod, with itsappendages, are represented Pl. XII. Fig. 3. It appeared to me, that thecombustion would be assisted by surrounding the flame of the lamp with asmall glass jar open at both ends, as represented in its place in Pl.XI.
I shall not enter into a more detailed description of the constructionof this apparatus, which is still capable of being altered and modifiedin many respects, but shall only add, that when it is to be used inexperiment, the lamp and reservoir with the contained oil must beaccurately weighed, after which it is placed as before directed, andlighted; having then formed the connection between the air in thegazometer and the lamp, the external jar A, Pl. XI. is fixed[Pg 432] over all,and secured by means of the board BC and two rods of iron which connectthis board with the lid, and are screwed to it. A small quantity of oilis burnt while the jar is adjusting to the lid, and the product of thatcombustion is lost; there is likewise a small portion of air from thegazometer lost at the same time. Both of these are of veryinconsiderable consequence in extensive experiments, and they are evencapable of being valued in our calculation of the results.
In a particular memoir, I shall give an account to the Academy of thedifficulties inseparable from this kind of experiments: These are soinsurmountable and troublesome, that I have not hitherto been able toobtain any rigorous determination of the quantities of the products. Ihave sufficient proof, however, that the fixed oils are entirelyresolved during combustion into water and carbonic acid gas, andconsequently that they are composed of hydrogen and charcoal; but I haveno certain knowledge respecting the proportions of these ingredients.[Pg 433]
The combustion of alkohol may be very readily performed in the apparatusalready described for the combustion of charcoal and phosphorus. A lampfilled with alkohol is placed under the jar A, Pl. IV. Fig. 3. a smallmorsel of phosphorus is placed upon the wick of the lamp, which is seton fire by means of the hot iron, as before directed. This process is,however, liable to considerable inconveniency; it is dangerous to makeuse of oxygen gas at the beginning of the experiment for fear ofdeflagration, which is even liable to happen when common air isemployed. An instance of this had very near proved fatal to myself, inpresence of some members of the Academy. Instead of preparing theexperiment, as usual, at the time it was to be performed, I had disposedevery thing in order the evening before; the atmospheric air of the jarhad thereby sufficient time to dissolve a good deal of the alkohol; andthis evaporation had even been considerably promoted by the height ofthe column of mercury, which I had raised to EF, Pl. IV. Fig. 3. Themoment I attempted[Pg 434] to set the little morsel of phosphorus on fire bymeans of the red hot iron, a violent explosion took place, which threwthe jar with great violence against the floor of the laboratory, anddashed it in a thousand pieces.
Hence we can only operate upon very small quantities, such as ten ortwelve grains of alkohol, in this manner; and the errors which may becommitted in experiments upon such small quantities prevents our placingany confidence in their results. I endeavoured to prolong thecombustion, in the experiments contained in the Memoirs of the Academyfor 1784, p. 593. by lighting the alkohol first in common air, andfurnishing oxygen gas afterwards to the jar, in proportion as itconsumed; but the carbonic acid gas produced by the process became agreat hinderance to the combustion, the more so that alkohol is butdifficultly combustible, especially in worse than common air; so thateven in this way very small quantities only could be burnt.
Perhaps this combustion might succeed better in the oil apparatus, Pl.XI.; but I have not hitherto ventured to try it. The jar A in which thecombustion is performed is near 1400 cubical inches in dimension; and,were an explosion to take place in such a vessel, its consequences wouldbe very terrible, and very difficult to guard against. I have not,however, despaired of making the attempt.[Pg 435]
From all these difficulties, I have been hitherto obliged to confinemyself to experiments upon very small quantities of alkohol, or at leastto combustions made in open vessels, such as that represented in Pl. IX.Fig. 5. which will be described in Section VII. of this chapter. If I amever able to remove these difficulties, I shall resume thisinvestigation.
Tho' the combustion of ether in close vessels does not present the samedifficulties as that of alkohol, yet it involves some of a differentkind, not more easily overcome, and which still prevent the progress ofmy experiments. I endeavoured to profit by the property which etherpossesses of dissolving in atmospheric air, and rendering it inflammablewithout explosion. For this purpose, I constructed the reservoir ofethera b c d, Plate XII. Fig. 8. to which air is brought from thegazometer by the tube 1, 2, 3, 4. This air spreads, in the first place,in the double lidac of the reservoir, from which it passes throughseven tubesef,gh,ik, &c. which descend to the bottom of theether, and it is[Pg 436] forced by the pressure of the gazometer to boil upthrough the ether in the reservoir. We may replace the ether in thisfirst reservoir, in proportion as it is dissolved and carried off by theair, by means of the supplementary reservoir E, connected by a brasstube fifteen or eighteen inches long, and shut by a stop-cock. Thislength of the connecting tube is to enable the descending ether toovercome the resistance occasioned by the pressure of the air from thegazometer.
The air, thus loaded with vapours of ether, is conducted by the tube 5,6, 7, 8, 9, to the jar A, into which it is allowed to escape through acapillary opening, at the extremity of which it is set on fire. The air,when it has served the purpose of combustion, passes through the bottle16, Pl. XI. the worm 17, 18, and the deliquescent tube 19, 20, afterwhich it passes through the alkaline bottles; in these its carbonic acidgas is absorbed, the water formed during the experiment having beenpreviously deposited in the former parts of the apparatus.
When I caused construct this apparatus, I supposed that the combinationof atmospheric air and ether formed in the reservoira b c d, Pl. XII.Fig. 8. was in proper proportion for supporting combustion; but in thisI was mistaken; for there is a very considerable quantity of excess ofether; so that an additional quantity of atmospheric[Pg 437] air is necessaryto enable it to burn fully. Hence a lamp constructed upon theseprinciples will burn in common air, which furnishes the quantity ofoxygen necessary for combustion, but will not burn in close vessels inwhich the air is not renewed. From this circumstance, my ether lamp wentout soon after being lighted and shut up in the jar A, Pl. XII. Fig. 8.To remedy this defect, I endeavoured to bring atmospheric air to thelamp by the lateral tube 10, 11, 12, 13, 14, 15, which I distributedcircularly round the flame; but the flame is so exceedingly rare, thatit is blown out by the gentlest possible stream of air, so that I havenot hitherto succeeded in burning ether. I do not, however, despair ofbeing able to accomplish it by means of some changes I am about to havemade upon this apparatus.
In the formation of water, two substances, hydrogen and oxygen, whichare both in the aëriform state before combustion, are transformed intoliquid or water by the operation.[Pg 438] This experiment would be very easy,and would require very simple instruments, if it were possible toprocure the two gasses perfectly pure, so that they might burn withoutany residuum. We might, in that case, operate in very small vessels,and, by continually furnishing the two gasses in proper proportions,might continue the combustion indefinitely. But, hitherto, chemists haveonly employed oxygen gas, mixed with azotic gas; from whichcircumstance, they have only been able to keep up the combustion ofhydrogen gas for a very limited time in close vessels, because, as theresiduum of azotic gas is continually increasing, the air becomes atlast so much contaminated, that the flame weakens and goes out. Thisinconvenience is so much the greater in proportion as the oxygen gasemployed is less pure. From this circumstance, we must either besatisfied with operating upon small quantities, or must exhaust thevessels at intervals, to get rid of the residuum of azotic gas; but, inthis case, a portion of the water formed during the experiment isevaporated by the exhaustion; and the resulting error is the moredangerous to the accuracy of the process, that we have no certain meansof valuing it.
These considerations make me desirous to repeat the principalexperiments of pneumatic chemistry with oxygen gas entirely free from[Pg 439]any admixture of azotic gas; and this may be procured from oxygenatedmuriat of potash. The oxygen gas extracted from this salt does notappear to contain azote, unless accidentally, so that, by properprecautions, it may be obtained perfectly pure. In the mean time, theapparatus employed by Mr Meusnier and me for the combustion of hydrogengas, which is described in the experiment for recomposition of water,Part I. Chap. VIII. and need not be here repeated, will answer thepurpose; when pure gasses are procured, this apparatus will require noalterations, except that the capacity of the vessels may then bediminished. See Pl. IV. Fig. 5.
The combustion, when once begun, continues for a considerable time, butweakens gradually, in proportion as the quantity of azotic gas remainingfrom the combustion increases, till at last the azotic gas is in suchover proportion that the combustion can no longer be supported, and theflame goes out. This spontaneous extinction must be prevented, because,as the hydrogen gas is pressed upon in its reservoir, by an inch and ahalf of water, whilst the oxygen gas suffers a pressure only of threelines, a mixture of the two would take place in the balloon, which wouldat last be forced by the superior pressure into the reservoir of oxygengas. Wherefore the combustion must be stopped,[Pg 440] by shutting thestop-cock of the tubedDd whenever the flame grows very feeble; forwhich purpose it must be attentively watched.
There is another apparatus for combustion, which, though we cannot withit perform experiments with the same scrupulous exactness as with thepreceding instruments, gives very striking results that are extremelyproper to be shewn in courses of philosophical chemistry. It consists ofa worm EF, Pl. IX. Fig. 5. contained in a metallic cooller ABCD. To theupper part of this worm E, the chimney GH is fixed, which is composed oftwo tubes, the inner of which is a continuation of the worm, and theouter one is a case of tin-plate, which surrounds it at about an inchdistance, and the interval is filled up with sand. At the inferiorextremity K of the inner tube, a glass tube is fixed, to which we adoptthe Argand lamp LM for burning alkohol, &c.
Things being thus disposed, and the lamp being filled with a determinatequantity of alkohol, it is set on fire; the water which is formed duringthe combustion rises in the chimney KE, and being condensed in the worm,runs out at its extremity F into the bottle P. The double tube of thechimney, filled with sand in the interstice, is to prevent the tube fromcooling in its upper part, and condensing the water; otherwise,[Pg 441] itwould fall back in the tube, and we should not be able to ascertain itsquantity, and besides it might fall in drops upon the wick, andextinguish the flame. The intention of this construction, is to keep thechimney always hot, and the worm always cool, that the water may bepreserved in the state of vapour whilst rising, and may be condensedimmediately upon getting into the descending part of the apparatus. Bythis instrument, which was contrived by Mr Meusnier, and which isdescribed by me in the Memoirs of the Academy for 1784, p. 593. we may,with attention to keep the worm always cold, collect nearly seventeenounces of water from the combustion of sixteen ounces of alkohol.
The termoxydation orcalcination is chiefly used to signify theprocess by which metals exposed to a certain degree of heat areconverted into oxyds, by absorbing oxygen from the air. This combinationtakes place in consequence of oxygen possessing a greater affinity tometals, at a certain temperature, than to caloric, which[Pg 442] becomesdisengaged in its free state; but, as this disengagement, when made incommon air, is slow and progressive, it is scarcely evident to thesenses. It is quite otherwise, however, when oxydation takes place inoxygen gas; for, being produced with much greater rapidity, it isgenerally accompanied with heat and light, so as evidently to show thatmetallic substances are real combustible bodies.
All the metals have not the same degree of affinity to oxygen. Gold,silver, and platina, for instance, are incapable of taking it away fromits combination with caloric, even in the greatest known heat; whereasthe other metals absorb it in a larger or smaller quantity, until theaffinities of the metal to oxygen, and of the latter to caloric, are inexact equilibrium. Indeed, this state of equilibrium of affinities maybe assumed as a general law of nature in all combinations.
In all operations of this nature, the oxydation of metals is acceleratedby giving free access to the air; it is sometimes much assisted byjoining the action of a bellows, which directs a stream of air over thesurface of the metal. This process becomes greatly more rapid if astream of oxygen gas be used, which is readily done by means of thegazometer formerly described. The metal, in this case, throws out abrilliant flame, and the oxydation is very quickly[Pg 443] accomplished; butthis method can only be used in very confined experiments, on account ofthe expence of procuring oxygen gas. In the essay of ores, and in allthe common operations of the laboratory, the calcination or oxydation ofmetals is usually performed in a dish of baked clay, Pl. IV. Fig. 6.commonly called aroasting test, placed in a strong furnace. Thesubstances to be oxydated are frequently stirred, on purpose to presentfresh surfaces to the air.
Whenever this operation is performed upon a metal which is not volatile,and from which nothing flies off into the surrounding air during theprocess, the metal acquires additional weight; but the cause of thisincreased weight during oxydation could never have been discovered bymeans of experiments performed in free air; and it is only since theseoperations have been performed in close vessels, and in determinatequantities of air, that any just conjectures have been formed concerningthe cause of this phenomenon. The first method for this purpose is dueto Dr Priestley, who exposes the metal to be calcined in a porcelain cupN, Pl. IV. Fig. 11. placed upon the stand IK, under a jar A, in thebason BCDE, full of water; the water is made to rise up to GH, bysucking out the air with a syphon, and the focus of a burning glass ismade to fall upon the metal. In a few minutes the oxydation takesplace,[Pg 444] a part of the oxygen contained in the air combines with themetal, and a proportional diminution of the volume of air is produced;what remains is nothing more than azotic gas, still however mixed with asmall quantity of oxygen gas. I have given an account of a series ofexperiments made with this apparatus in my Physical and Chemical Essays,first published in 1773. Mercury may be used instead of water in thisexperiment, whereby the results are rendered still more conclusive.
Another process for this purpose was invented by Mr Boyle, and of whichI gave an account in the Memoirs of the Academy for 1774, p. 351. Themetal is introduced into a retort, Pl. III. Fig. 20. the beak of whichis hermetically sealed; the metal is then oxydated by means of heatapplied with great precaution. The weight of the vessel, and itscontained substances, is not at all changed by this process, until theextremity of the neck of the retort is broken; but, when that is done,the external air rushes in with a hissing noise. This operation isattended with danger, unless a part of the air is driven out of theretort, by means of heat, before it is hermetically sealed, as otherwisethe retort would be apt to burst by the dilation of the air when placedin the furnace. The quantity of air driven out may be received under ajar in the pneumato-chemical apparatus,[Pg 445] by which its quantity, and thatof the air remaining in the retort, is ascertained. I have notmultiplied my experiments upon oxydation of metals so much as I couldhave wished; neither have I obtained satisfactory results with any metalexcept tin. It is much to be wished that some person would undertake aseries of experiments upon oxydation of metals in the several gasses;the subject is important, and would fully repay any trouble which thiskind of experiment might occasion.
As all the oxyds of mercury are capable of revivifying without addition,and restore the oxygen gas they had before absorbed, this seemed to bethe most proper metal for becoming the subject of conclusive experimentsupon oxydation. I formerly endeavoured to accomplish the oxydation ofmercury in close vessels, by filling a retort, containing a smallquantity of mercury, with oxygen gas, and adapting a bladder half fullof the same gas to its beak; See Pl. IV. Fig. 12. Afterwards, by heatingthe mercury in the retort for a very long time, I succeeded in oxydatinga very small portion, so as to form a little red oxyd floating upon thesurface of the running mercury; but the quantity was so small, that thesmallest error committed in the determination of the quantities ofoxygen gas before and after the operation must have thrown very greatuncertainty upon the[Pg 446] results of the experiment. I was, besides,dissatisfied with this process, and not without cause, lest any airmight have escaped through the pores of the bladder, more especially asit becomes shrivelled by the heat of the furnace, unless covered overwith cloths kept constantly wet.
This experiment is performed with more certainty in the apparatusdescribed in the Memoirs of the Academy for 1775, p. 580. This consistsof a retort, A, Pl. IV. Fig. 2. having a crooked glass tube BCDE of tenor twelve lines internal diameter, melted on to its beak, and which isengaged under the bell glass FG, standing with its mouth downwards, in abason filled with water or mercury. The retort is placed upon the barsof the furnace MMNN, Pl. IV. Fig. 2. or in a sand bath, and by means ofthis apparatus we may, in the course of several days, oxydate a smallquantity of mercury in common air; the red oxyd floats upon the surface,from which it may be collected and revivified, so as to compare thequantity of oxygen gas obtained in revivification with the absorptionwhich took place during oxydation. This kind of experiment can only beperformed upon a small scale, so that no very certain conclusions can bedrawn from them[61].
The combustion of iron in oxygen gas being a true oxydation of thatmetal, ought to be mentioned in this place. The apparatus employed by MrIngenhousz for this operation is represented in Pl. IV. Fig. 17.; but,having already described it sufficiently in Chap. III. I shall refer thereader to what is said of it in that place. Iron may likewise beoxydated by combustion in vessels filled with oxygen gas, in the wayalready directed for phosphorus and charcoal. This apparatus isrepresented Pl. IV. Fig. 3. and described in the fifth chapter of thefirst part of this work. We learn from Mr Ingenhousz, that all themetals, except gold, silver, and mercury, may be burnt or oxydated inthe same manner, by reducing them into very fine wire, or very thinplates cut into narrow slips; these are twisted round with iron-wire,which communicates the property of burning to the other metals.
Mercury is even difficultly oxydated in free air. In chemicallaboratories, this process is usually carried on in a matrass A, Pl. IV.Fig. having a very flat body, and a very long neck BC, which vessel iscommonly calledBoyle's bell. A quantity of mercury is introducedsufficient to cover the bottom, and it is placed in a sand-bath, whichkeeps up a constant heat approaching to that of boiling mercury. Bycontinuing this operation with five or six similar matrasses duringseveral months, and renewing[Pg 448] the mercury from time to time, a fewounces of red oxyd are at last obtained. The great slowness andinconvenience of this apparatus arises from the air not beingsufficiently renewed; but if, on the other hand, too free a circulationwere given to the external air, it would carry off the mercury insolution in the state of vapour, so that in a few days none would remainin the vessel.
As, of all the experiments upon the oxydation of metals, those withmercury are the most conclusive, it were much to be wished that a simpleapparatus could be contrived by which this oxydation and its resultsmight be demonstrated in public courses of chemistry. This might, in myopinion, be accomplished by methods similar to those I have alreadydescribed for the combustion of charcoal and the oils; but, from otherpursuits, I have not been able hitherto to resume this kind ofexperiment.
The oxyd of mercury revives without addition, by being heated to aslightly red heat. In this degree of temperature, oxygen has greateraffinity to caloric than to mercury, and forms oxygen gas. This isalways mixed with a small portion of azotic gas, which indicates thatthe mercury absorbs a small portion of this latter gas during oxydation.It almost always contains a little carbonic acid gas, which mustundoubtedly be attributed to the foulnesses of the[Pg 449] oxyd; these arecharred by the heat, and convert a part of the oxygen gas into carbonicacid.
If chemists were reduced to the necessity of procuring all the oxygengas employed in their experiments from mercury oxydated by heat withoutaddition, or, as it is called,calcined orprecipitated per se, theexcessive dearness of that preparation would render experiments, evenupon a moderate scale, quite impracticable. But mercury may likewise beoxydated by means of nitric acid; and in this way we procure a red oxyd,even more pure than that produced by calcination. I have sometimesprepared this oxyd by dissolving mercury in nitric acid, evaporating todryness, and calcining the salt, either in a retort, or in capsulesformed of pieces of broken matrasses and retorts, in the manner formerlydescribed; but I have never succeeded in making it equally beautifulwith what is sold by the druggists, and which is, I believe, broughtfrom Holland. In choosing this, we ought to prefer what is in solidlumps composed of soft adhering scales, as when in powder it issometimes adulterated with red oxyd of lead.
To obtain oxygen gas from the red oxyd of mercury, I usually employ aporcelain retort, having a long glass tube adapted to its beak, which isengaged under jars in the water pneumato-chemical[Pg 450] apparatus, and Iplace a bottle in the water, at the end of the tube, for receiving themercury, in proportion as it revives and distils over. As the oxygen gasnever appears till the retort becomes red, it seems to prove theprinciple established by Mr Berthollet, that an obscure heat can neverform oxygen gas, and that light is one of its constituent elements. Wemust reject the first portion of gas which comes over, as being mixedwith common air, from what was contained in the retort at the beginningof the experiment; but, even with this precaution, the oxygen gasprocured is usually contaminated with a tenth part of azotic gas, andwith a very small portion of carbonic acid gas. This latter is readilygot rid of, by making the gas pass through a solution of caustic alkali;but we know of no method for separating the azotic gas; its proportionsmay however be ascertained, by leaving a known quantity of the oxygengas contaminated with it for a fortnight, in contact with sulphuret ofsoda or potash, which absorbs the oxygen gas so as to convert thesulphur into sulphuric acid, and leaves the azotic gas remaining pure.
We may likewise procure oxygen gas from black oxyd of manganese ornitrat of potash, by exposing them to a red heat in the apparatusalready described for operating upon red[Pg 451] oxyd of mercury; only, as itrequires such a heat as is at least capable of softening glass, we mustemploy retorts of stone or of porcelain. But the purest and best oxygengas is what is disengaged from oxygenated muriat of potash by simpleheat. This operation is performed in a glass retort, and the gasobtained is perfectly pure, provided that the first portions, which aremixed with the common air of the vessels, be rejected.
[61] See an account of this experiment, Part. I. Chap.iii.—A.
I have already shown, Part I. Chap. IX. that oxygen does not always partwith the whole of the caloric it contained in the state of gas when itenters into combination with other bodies. It carries almost the wholeof its caloric alongst with it in entering into the combinations whichform nitric acid and oxygenated muriatic acid; so that in nitrats, andmore especially in oxygenated muriats, the oxygen is, in a certaindegree, in the state of oxygen gas, condensed, and reduced to thesmallest volume it is capable of occupying.
In these combinations, the caloric exerts a constant action upon theoxygen to bring it back to the state of gas; hence the oxygen adheresbut very slightly, and the smallest additional force is capable ofsetting it free; and, when such force is applied, it often recovers thestate of gas instantaneously. This rapid passage from the solid to theaëriform state is called detonation, or fulmination, because it isusually accompanied with noise and explosion. Deflagrations are commonlyproduced by means of combinations of charcoal either with nitre or[Pg 453]oxygenated muriat of potash; sometimes, to assist the inflammation,sulphur is added; and, upon the just proportion of these ingredients,and the proper manipulation of the mixture, depends the art of makinggun-powder.
As oxygen is changed, by deflagration with charcoal, into carbonic acid,instead of oxygen gas, carbonic acid gas is disengaged, at least whenthe mixture has been made in just proportions. In deflagration withnitre, azotic gas is likewise disengaged, because azote is one of theconstituent elements of nitric acid.
The sudden and instantaneous disengagement and expansion of these gassesis not, however, sufficient for explaining all the phenomena ofdeflagration; because, if this were the sole operating power, gun powderwould always be so much the stronger in proportion as the quantity ofgas disengaged in a given time was the more considerable, which does notalways accord with experiment. I have tried some kinds which producedalmost double the effect of ordinary gun powder, although they gave outa sixth part less of gas during deflagration. It would appear that thequantity of caloric disengaged at the moment of detonation contributesconsiderably to the expansive effects produced; for, although caloricpenetrates freely through the pores of every body in nature, it can onlydo so progressively, and in a given time; hence,[Pg 454] when the quantitydisengaged at once is too large to get through the pores of thesurrounding bodies, it must necessarily act in the same way withordinary elastic fluids, and overturn every thing that opposes itspassage. This must, at least in part, take place when gun-powder is seton fire in a cannon; as, although the metal is permeable to caloric, thequantity disengaged at once is too large to find its way through thepores of the metal, it must therefore make an effort to escape on everyside; and, as the resistance all around, excepting towards the muzzle,is too great to be overcome, this effort is employed for expelling thebullet.
The caloric produces a second effect, by means of the repulsive forceexerted between its particles; it causes the gasses, disengaged at themoment of deflagration, to expand with a degree of force proportioned tothe temperature produced.
It is very probable that water is decomposed during the deflagration ofgun-powder, and that part of the oxygen furnished to the nascentcarbonic acid gas is produced from it. If so, a considerable quantity ofhydrogen gas must be disengaged in the instant of deflagration, whichexpands, and contributes to the force of the explosion. It may readilybe conceived how greatly this circumstance must increase the effect ofpowder, if we consider that a pint of hydrogen[Pg 455] gas weighs only onegrain and two thirds; hence a very small quantity in weight must occupya very large space, and it must exert a prodigious expansive force inpassing from the liquid to the aëriform state of existence.
In the last place, as a portion of undecomposed water is reduced tovapour during the deflagration of gun-powder, and as water, in the stateof gas, occupies seventeen or eighteen hundred times more space than inits liquid state, this circumstance must likewise contribute largely tothe explosive force of the powder.
I have already made a considerable series of experiments upon the natureof the elastic fluids disengaged during the deflagration of nitre withcharcoal and sulphur; and have made some, likewise, with the oxygenatedmuriat of potash. This method of investigation leads to tollerablyaccurate conclusions with respect to the constituent elements of thesesalts. Some of the principal results of these experiments, and of theconsequences drawn from them respecting the analysis of nitric acid, arereported in the collection of memoirs presented to the Academy byforeign philosophers, vol. xi. p. 625. Since then I have procured moreconvenient instruments, and I intend to repeat these experiments upon alarger scale, by which I shall procure more accurate precision in theirresults; the following, however, is the process I have hitherto[Pg 456]employed. I would very earnestly advise such as intend to repeat some ofthese experiments, to be very much upon their guard in operating uponany mixture which contains nitre, charcoal, and sulphur, and moreespecially with those in which oxygenated muriat of potash is mixed withthese two materials.
I make use of pistol barrels, about six inches long, and of five or sixlines diameter, having the touch-hole spiked up with an iron nailstrongly driven in, and broken in the hole, and a little tin-smith'ssolder run in to prevent any possible issue for the air. These arecharged with a mixture of known quantities of nitre and charcoal, or anyother mixture capable of deflagration, reduced to an impalpable powder,and formed into a paste with a moderate quantity of water. Every portionof the materials introduced must be rammed down with a rammer nearly ofthe same caliber with the barrel, four or five lines at the muzzle mustbe left empty, and about two inches of quick match are added at the endof the charge. The only difficulty in this experiment, especially whensulphur is contained in the mixture, is to discover the proper degree ofmoistening; for, if the paste be too much wetted, it will not take fire,and if too dry, the deflagration is apt to become too rapid, and evendangerous.[Pg 457]
When the experiment is not intended to be rigorously exact, we set fireto the match, and, when it is just about to communicate with the charge,we plunge the pistol below a large bell-glass full of water, in thepneumato chemical apparatus. The deflagration begins, and continues inthe water, and gas is disengaged with less or more rapidity, inproportion as the mixture is more or less dry. So long as thedeflagration continues, the muzzle of the pistol must be kept somewhatinclined downwards, to prevent the water from getting into its barrel.In this manner I have sometimes collected the gas produced from thedeflagration of an ounce and half, or two ounces, of nitre.
In this manner of operating it is impossible to determine the quantityof carbonic acid gas disengaged, because a part of it is absorbed by thewater while passing through it; but, when the carbonic acid is absorbed,the azotic gas remains; and, if it be agitated for a few minutes incaustic alkaline solution, we obtain it pure, and can easily determineits volume and weight. We may even, in this way, acquire a tollerablyexact knowledge of the quantity of carbonic acid by repeating theexperiment a great many times, and varying the proportions of charcoal,till we find the exact quantity requisite to deflagrate the whole nitreemployed. Hence, by means of the weight of charcoal employed, we[Pg 458]determine the weight of oxygen necessary for saturation, and deduce thequantity of oxygen contained in a given weight of nitre.
I have used another process, by which the results of this experiment areconsiderably more accurate, which consists in receiving the disengagedgasses in bell-glasses filled with mercury. The mercurial apparatus Iemploy is large enough to contain jars of from twelve to fifteen pintsin capacity, which are not very readily managed when full of mercury,and even require to be filled by a particular method. When the jar isplaced in the cistern of mercury, a glass syphon is introduced,connected with a small air-pump, by means of which the air is exhausted,and the mercury rises so as to fill the jar. After this, the gas of thedeflagration is made to pass into the jar in the same manner as directedwhen water is employed.
I must again repeat, that this species of experiment requires to beperformed with the greatest possible precautions. I have sometimes seen,when the disengagement of gas proceeded with too great rapidity, jarsfilled with more than an hundred and fifty pounds of mercury driven offby the force of the explosion, and broken to pieces, while the mercurywas scattered about in great quantities.
When the experiment has succeeded, and the gas is collected under thejar, its quantity in[Pg 459] general, and the nature and quantities of theseveral species of gasses of which the mixture is composed, areaccurately ascertained by the methods already pointed out in the secondchapter of this part of my work. I have been prevented from putting thelast hand to the experiments I had begun upon deflagration, from theirconnection with the objects I am at present engaged in; and I am inhopes they will throw considerable light upon the operations belongingto the manufacture of gun-powder.
We have already seen, that, by aqueous solution, in which the particlesof bodies are separated from each other, neither the solvent nor thebody held in solution are at all decomposed; so that, whenever the causeof separation ceases, the particles reunite, and the saline substancerecovers precisely the same appearance and properties it possessedbefore solution. Real solutions are produced by fire, or by introducingand accumulating a great quantity of caloric between the particles ofbodies; and this species of solution in caloric is usually calledfusion.
This operation is commonly performed in vessels called crucibles, whichmust necessarily[Pg 461] be less fusible than the bodies they are intended tocontain. Hence, in all ages, chemists have been extremely solicitous toprocure crucibles of very refractory materials, or such as are capableof resisting a very high degree of heat. The best are made of very pureclay or of porcelain earth; whereas such as are made of clay mixed withcalcareous or silicious earth are very fusible. All the crucibles madein the neighbourhood of Paris are of this kind, and consequently unfitfor most chemical experiments. The Hessian crucibles are tolerably good;but the best are made of Limoges earth, which seems absolutelyinfusible. We have, in France, a great many clays very fit for makingcrucibles; such, for instance, is the kind used for making melting potsat the glass-manufactory of St Gobin.
Crucibles are made of various forms, according to the operations theyare intended to perform. Several of the most common kinds arerepresented Pl. VII. Fig. 7. 8. 9. and 10. the one represented at Fig.9. is almost shut at its mouth.
Though fusion may often take place without changing the nature of thefused body, this operation is frequently employed as a chemical means ofdecomposing and recompounding bodies. In this way all the metals areextracted from their ores; and, by this process, they are revivified,[Pg 462]moulded, and alloyed with each other. By this process sand and alkaliare combined to form glass, and by it likewise pastes, or colouredstones, enamels, &c. are formed.
The action of violent fire was much more frequently employed by theancient chemists than it is in modern experiments. Since greaterprecision has been employed in philosophical researches, thehumid hasbeen preferred to thedry method of process, and fusion is seldom hadrecourse to until all the other means of analysis have failed.
These are instruments of most universal use in chemistry; and, as thesuccess of a great number of experiments depends upon their being wellor ill constructed, it is of great importance that a laboratory be wellprovided in this respect. A furnace is a kind of hollow cylindricaltower, sometimes widened above, Pl. XIII. Fig. 1. ABCD, which must haveat least two lateral openings; one in its upper part F, which is thedoor of the fire-place, and one below, G, leading to the ash-hole.Between these the furnace[Pg 463] is divided by a horizontal grate, intendedfor supporting the fewel, the situation of which is marked in the figureby the line HI. Though this be the least complicated of all the chemicalfurnaces, yet it is applicable to a great number of purposes. By itlead, tin, bismuth, and, in general, every substance which does notrequire a very strong fire, may be melted in crucibles; it will servefor metallic oxydations, for evaporatory vessels, and for sand-baths, asin Pl. III. Fig. 1. and 2. To render it proper for these purposes,several notches,m m m m, Pl. XIII. Fig. 1. are made in its upperedge, as otherwise any pan which might be placed over the fire wouldstop the passage of the air, and prevent the fewel from burning. Thisfurnace can only produce a moderate degree of heat, because the quantityof charcoal it is capable of consuming is limited by the quantity of airwhich is allowed to pass through the opening G of the ash-hole. Itspower might be considerably augmented by enlarging this opening, butthen the great stream of air which is convenient for some operationsmight be hurtful in others; wherefore we must have furnaces of differentforms, constructed for different purposes, in our laboratories: Thereought especially to be several of the kind now described of differentsizes.
The reverberatory furnace, Pl. XIII. Fig. 2. is perhaps more necessary.This, like the common[Pg 464] furnace, is composed of the ash-hole HIKL, thefire-place KLMN, the laboratory MNOP, and the dome RRSS, with its funnelor chimney TTVV; and to this last several additional tubes may beadapted, according to the nature of the different experiments. Theretort A is placed in the division called the laboratory, and supportedby two bars of iron which run across the furnace, and its beak comes outat a round hole in the side of the furnace, one half of which is cut inthe piece called the laboratory, and the other in the dome. In most ofthe ready made reverberatory furnaces which are sold by the potters atParis, the openings both above and below are too small: These do notallow a sufficient volume of air to pass through; hence, as the quantityof charcoal consumed, or, what is much the same thing, the quantity ofcaloric disengaged, is nearly in proportion to the quantity of air whichpasses through the furnace, these furnaces do not produce a sufficienteffect in a great number of experiments. To remedy this defect, thereought to be two openings GG to the ash-hole; one of these is shut upwhen only a moderate fire is required; and both are kept open when thestrongest power of the furnace is to be exerted. The opening of the domeSS ought likewise to be considerably larger than is usually made.[Pg 465]
It is of great importance not to employ retorts of too large size inproportion to the furnace, as a sufficient space ought always to beallowed for the passage of the air between the sides of the furnace andthe vessel. The retort A in the figure is too small for the size of thefurnace, yet I find it more easy to point out the error than to correctit. The intention of the dome is to oblige the flame and heat tosurround and strike back or reverberate upon every part of the retort,whence the furnace gets the name of reverberatory. Without thiscircumstance the retort would only be heated in its bottom, the vapoursraised from the contained substance would condense in the upper part,and a continual cohabitation would take place without any thing passingover into the receiver, but, by means of the dome, the retort is equallyheated in every part, and the vapours being forced out, can onlycondense in the neck of the retort, or in the recipient.
To prevent the bottom of the retort from being either heated or coolledtoo suddenly, it is sometimes placed in a small sand-bath of baked clay,standing upon the cross bars of the furnace. Likewise, in manyoperations, the retorts are coated over with lutes, some of which areintended to preserve them from the too sudden influence of heat or ofcold, while others are for sustaining the glass, or forming a kind ofsecond[Pg 466] retort, which supports the glass one during operations whereinthe strength of the fire might soften it. The former is made ofbrick-clay with a little cow's hair beat up alongst with it, into apaste or mortar, and spread over the glass or stone retorts. The latteris made of pure clay and pounded stone-ware mixed together, and used inthe same manner. This dries and hardens by the fire, so as to form atrue supplementary retort capable of retaining the materials, if theglass retort below should crack or soften. But, in experiments which areintended for collecting gasses, this lute, being porous, is of no mannerof use.
In a great many experiments wherein very violent fire is not required,the reverberatory furnace may be used as a melting one, by leaving outthe piece called the laboratory, and placing the dome immediately uponthe fire-place, as represented Pl. XIII. Fig. 3. The furnace representedin Fig. 4. is very convenient for fusions; it is composed of thefire-place and ash-hole ABD, without a door, and having a hole E, whichreceives the muzzle of a pair of bellows strongly luted on, and the domeABGH, which ought to be rather lower than is represented in the figure.This furnace is not capable of producing a very strong heat, but issufficient for ordinary operations, and may be readily moved to any partof the laboratory[Pg 467] where it is wanted. Though these particular furnacesare very convenient, every laboratory must be provided with a forgefurnace, having a good pair of bellows, or, what is more necessary, apowerful melting furnace. I shall describe the one I use, with theprinciples upon which it is constructed.
The air circulates in a furnace in consequence of being heated in itspassage through the burning coals; it dilates, and, becoming lighterthan the surrounding air, is forced to rise upwards by the pressure ofthe lateral columns of air, and is replaced by fresh air from all sides,especially from below. This circulation of air even takes place whencoals are burnt in a common chaffing dish; but we can readily conceive,that, in a furnace open on all sides, the mass of air which passes, allother circumstances being equal, cannot be so great as when it isobliged to pass through a furnace in the shape of a hollow tower, likemost of the chemical furnaces, and consequently, that the combustionmust be more rapid in a furnace of this latter construction. Suppose,for instance, the furnace ABCDEF open above, and filled with burningcoals, the force with which the air passes through the coals will be inproportion to the difference between the specific gravity of two columnsequal to AC, the one of cold air without, and the other of heated airwithin the furnace.[Pg 468] There must be some heated air above the opening AB,and the superior levity of this ought likewise to be taken intoconsideration; but, as this portion is continually coolled and carriedoff by the external air, it cannot produce any great effect.
But, if we add to this furnace a large hollow tube GHAB of the samediameter, which preserves the air which has been heated by the burningcoals from being coolled and dispersed by the surrounding air, thedifference of specific gravity which causes the circulation will then bebetween two columns equal to GC. Hence, if GC be three times the lengthof AC, the circulation will have treble force. This is upon thesupposition that the air in GHCD is as much heated as what is containedin ABCD, which is not strictly the case, because the heat must decreasebetween AB and GH; but, as the air in GHAB is much warmer than theexternal air, it follows, that the addition of the tube must increasethe rapidity of the stream of air, that a larger quantity must passthrough the coals, and consequently that a greater degree of combustionmust take place.
We must not, however, conclude from these principles, that the length ofthis tube ought to be indefinitely prolonged; for, since the heat of theair gradually diminishes in passing from AB to GH, even from the contactof the sides of the[Pg 469] tube, if the tube were prolonged to a certaindegree, we would at last come to a point where the specific gravity ofthe included air would be equal to the air without; and, in this case,as the cool air would no longer tend to rise upwards, it would become agravitating mass, resisting the ascension of the air below. Besides, asthis air, which has served for combustion, is necessarily mixed withcarbonic acid gas, which is considerably heavier than common air, if thetube were made long enough, the air might at last approach so near tothe temperature of the external air as even to gravitate downwards;hence we must conclude, that the length of the tube added to a furnacemust have some limit beyond which it weakens, instead of strengtheningthe force of the fire.
From these reflections it follows, that the first foot of tube added toa furnace produces more effect than the sixth, and the sixth more thanthe tenth; but we have no data to ascertain at what height we ought tostop. This limit of useful addition is so much the farther in proportionas the materials of the tube are weaker conductors of heat, because theair will thereby be so much less coolled; hence baked earth is much tobe preferred to plate iron. It would be even of consequence to make thetube double, and to fill the interval with rammed charcoal, which is oneof the worst conductors of heat[Pg 470] known; by this the refrigeration of theair will be retarded, and the rapidity of the stream of air consequentlyincreased; and, by this means, the tube may be made so much the longer.
As the fire-place is the hottest part of a furnace, and the part wherethe air is most dilated in its passage, this part ought to be made witha considerable widening or belly. This is the more necessary, as it isintended to contain the charcoal and crucible, as well as for thepassage of the air which supports, or rather produces the combustion;hence we only allow the interstices between the coals for the passage ofthe air.
From these principles my melting furnace is constructed, which I believeis at least equal in power to any hitherto made, though I by no meanspretend that it possesses the greatest possible intensity that can beproduced in chemical furnaces. The augmentation of the volume of airproduced during its passage through a melting furnace not being hithertoascertained from experiment, we are still unacquainted with theproportions which should exist between the inferior and superiorapertures, and the absolute size of which these openings should be madeis still less understood; hence data are wanting by which to proceedupon principle, and we can only accomplish the end in view by repeatedtrials.[Pg 471]
This furnace, which, according to the above stated rules, is in form ofan eliptical spheroid, is represented Pl. XIII. Fig. 6. ABCD; it is cutoff at the two ends by two plains, which pass, perpendicular to theaxis, through the foci of the elipse. From this shape it is capable ofcontaining a considerable quantity of charcoal, while it leavessufficient space in the intervals for the passage of the air. That noobstacle may oppose the free access of external air, it is perfectlyopen below, after the model of Mr Macquer's melting furnace, and standsupon an iron tripod. The grate is made of flat bars set on edge, andwith considerable interstices. To the upper part is added a chimney, ortube, of baked earth, ABFG, about eighteen feet long, and almost halfthe diameter of the furnace. Though this furnace produces a greater heatthan any hitherto employed by chemists, it is still susceptible of beingconsiderably increased in power by the means already mentioned, theprincipal of which is to render the tube as bad a conductor of heat aspossible, by making it double, and filling the interval with rammedcharcoal.
When it is required to know if lead contains any mixture of gold orsilver, it is heated in a strong fire in capsules of calcined bones,which are called cuppels. The lead is oxydated, becomes vitrified, andsinks into the substance of[Pg 472] the cuppel, while the gold or silver, beingincapable of oxydation, remain pure. As lead will not oxydate withoutfree access of air, this operation cannot be performed in a crucibleplaced in the middle of the burning coals of a furnace, because theinternal air, being mostly already reduced by the combustion into azoticand carbonic acid gas, is no longer fit for the oxydation of metals. Itwas therefore necessary to contrive a particular apparatus, in which themetal should be at the same time exposed to the influence of violentheat, and defended from contact with air rendered incombustible by itspassage through burning coals. The furnace intended for answering thisdouble purpose is called the cuppelling or essay furnace. It is usuallymade of a square form, as represented Pl. XIII. Fig. 8. and 10. havingan ash-hole AABB, a fire-place BBCC, a laboratory CCDD, and a dome DDEE.The muffle or small oven of baked earth GH, Fig. 9. being placed in thelaboratory of the furnace upon cross bars of iron, is adjusted to theopening GG, and luted with clay softened in water. The cuppels areplaced in this oven or muffle, and charcoal is conveyed into the furnacethrough the openings of the dome and fire-place. The external air entersthrough the openings of the ash-hole for supporting the combustion, andescapes by the superior opening or chimney at EE; and air is[Pg 473] admittedthrough the door of the muffle GG for oxydating the contained metal.
Very little reflection is sufficient to discover the erroneousprinciples upon which this furnace is constructed. When the opening GGis shut, the oxydation is produced slowly, and with difficulty, for wantof air to carry it on; and, when this hole is open, the stream of coldair which is then admitted fixes the metal, and obstructs the process.These inconveniencies may be easily remedied, by constructing the muffleand furnace in such a manner that a stream of fresh external air shouldalways play upon the surface of the metal, and this air should be madeto pass through a pipe of clay kept continually red hot by the fire ofthe furnace. By this means the inside of the muffle will never becoolled, and processes will be finished in a few minutes, which atpresent require a considerable space of time.
Mr Sage remedies these inconveniencies in a different manner; he placesthe cuppel containing lead, alloyed with gold or silver, amongst thecharcoal of an ordinary furnace, and covered by a small porcelainmuffle; when the whole is sufficiently heated, he directs the blast of acommon pair of hand-bellows upon the surface of the metal, and completesthe cuppellation in this way with great ease and exactness.[Pg 474]
By means of large burning glasses, such as those of Tchirnausen and Mrde Trudaine, a degree of heat is obtained somewhat greater than hashitherto been produced in chemical furnaces, or even in the ovens offurnaces used for baking hard porcelain. But these instruments areextremely expensive, and do not even produce heat sufficient to meltcrude platina; so that their advantages are by no means sufficient tocompensate for the difficulty of procuring, and even of using them.Concave mirrors produce somewhat more effect than burning glasses of thesame diameter, as is proved by the experiments of Messrs Macquer andBeaumé with the speculum of the Abbé Bouriot; but, as the direction ofthe reflected rays is necessarily from below upwards, the substance tobe operated upon must be placed in the air without any support, whichrenders most chemical experiments impossible to be performed with thisinstrument.[Pg 475]
For these reasons, I first endeavoured to employ oxygen gas forcombustion, by filling large bladders with it, and making it passthrough a tube capable of being shut by a stop-cock; and in this way Isucceeded in causing it to support the combustion of lighted charcoal.The intensity of the heat produced, even in my first attempt, was sogreat as readily to melt a small quantity of crude platina. To thesuccess of this attempt is owing the idea of the gazometer, described p.308.et seq. which I substituted instead of the bladders; and, as wecan give the oxygen gas any necessary degree of pressure, we can withthis instrument keep up a continued stream, and give it even a veryconsiderable force.
The only apparatus necessary for experiments of this kind consists of asmall table ABCD, Pl. XII. Fig. 15, with a hole F, through which passesa tube of copper or silver, ending in a very small opening at G, andcapable of being opened or shut by the stop-cock H. This tube iscontinued below the table atl m n o, and is connected with theinterior cavity of the gazometer. When we mean to operate, a hole of afew lines deep must be made with a chizel in a piece of charcoal, intowhich the substance to be treated is laid; the charcoal is set on fireby means of a candle and blow-pipe, after which it is exposed[Pg 476] to arapid stream of oxygen gas from the extremity G of the tube FG.
This manner of operating can only be used with such bodies as can beplaced, without inconvenience, in contact with charcoal, such as metals,simple earths, &c. But, for bodies whose elements have affinity tocharcoal, and which are consequently decomposed by that substance, suchas sulphats, phosphats, and most of the neutral salts, metallic glasses,enamels, &c. we must use a lamp, and make the stream of oxygen gas passthrough its flame. For this purpose, we use the elbowed blow-pipe ST,instead of the bent one FG, employed with charcoal. The heat produced inthis second manner is by no means so intense as in the former way, andis very difficultly made to melt platina. In this manner of operatingwith the lamp, the substances are placed in cuppels of calcined bones,or little cups of porcelain, or even in metallic dishes. If these lastare sufficiently large, they do not melt, because, metals being goodconductors of heat, the caloric spreads rapidly through the whole mass,so that none of its parts are very much heated.
In the Memoirs of the Academy for 1782, p. 476. and for 1783, p. 573.the series of experiments I have made with this apparatus may be seen atlarge. The following are some of the principal results.[Pg 477]
1. Rock cristal, or pure silicious earth, is infusible, but becomescapable of being softened or fused when mixed with other substances.
2. Lime, magnesia, and barytes, are infusible, either when alone, orwhen combined together; but, especially lime, they assist the fusion ofevery other body.
3. Argill, or pure base of alum, is completely fusibleper se into avery hard opake vitreous substance, which scratches glass like theprecious stones.
4. All the compound earths and stones are readily fused into a brownishglass.
5. All the saline substances, even fixed alkali, are volatilized in afew seconds.
6. Gold, silver, and probably platina, are slowly volatilized withoutany particular phenomenon.
7. All other metallic substances, except mercury, become oxydated,though placed upon charcoal, and burn with different coloured flames,and at last dissipate altogether.
8. The metallic oxyds likewise all burn with flames. This seems to forma distinctive character for these substances, and even leads me tobelieve, as was suspected by Bergman, that barytes is a metallic oxyd,though we have not hitherto been able to obtain the metal in its pure orreguline state.[Pg 478]
9. Some of the precious stones, as rubies, are capable of being softenedand soldered together, without injuring their colour, or evendiminishing their weights. The hyacinth, tho' almost equally fixed withthe ruby, loses its colour very readily. The Saxon and Brasilian topaz,and the Brasilian ruby, lose their colour very quickly, and lose about afifth of their weight, leaving a white earth, resembling white quartz,or unglazed china. The emerald, chrysolite, and garnet, are almostinstantly melted into an opake and coloured glass.
10. The diamond presents a property peculiar to itself; it burns in thesame manner with combustible bodies, and is entirely dissipated.
There is yet another manner of employing oxygen gas for considerablyincreasing the force of fire, by using it to blow a furnace. Mr Achardfirst conceived this idea; but the process he employed, by which hethought to dephlogisticate, as it is called, atmospheric air, or todeprive it of azotic gas, is absolutely unsatisfactory. I propose toconstruct a very simple furnace, for this purpose, of very refractoryearth, similar to the one represented Pl. XIII. Fig. 4. but smaller inall its dimensions. It is to have two openings, as at E, through one ofwhich the nozle of a pair of bellows is to pass, by which the heat is tobe raised as high as possible with common air; after which, the[Pg 479] streamof common air from the bellows being suddenly stopt, oxygen gas is to beadmitted by a tube, at the other opening, communicating with a gazometerhaving the pressure of four or five inches of water. I can in thismanner unite the oxygen gas from several gazometers, so as to make eightor nine cubical feet of gas pass through the furnace; and in this way Iexpect to produce a heat greatly more intense than any hitherto known.The upper orifice of the furnace must be carefully made of considerabledimensions, that the caloric produced may have free issue, lest the toosudden expansion of that highly elastic fluid should produce a dangerousexplosion.
| Twelfth Parts of a Line. | Decimal Fractions. | Lines. | Decimal Fractions. |
| 1 | 0.00694 | 1 | 0.08333 |
| 2 | 0.01389 | 2 | 0.16667 |
| 3 | 0.02083 | 3 | 0.25000 |
| 4 | 0.02778 | 4 | 0.33333 |
| 5 | 0.03472 | 5 | 0.41667 |
| 6 | 0.04167 | 6 | 0.50000 |
| 7 | 0.04861 | 7 | 0.58333 |
| 8 | 0.05556 | 8 | 0.66667 |
| 9 | 0.06250 | 9 | 0.75000 |
| 10 | 0.06944 | 10 | 0.83333 |
| 11 | 0.07639 | 11 | 0.91667 |
| 12 | 0.08333 | 12 | 1.00000 |
| Water. | Mercury. | Water. | Mercury. |
| .1 | .00737 | 4. | .29480 |
| .2 | .01474 | 5. | .36851 |
| .3 | .02201 | 6. | .44221 |
| .4 | .02948 | 7. | .51591 |
| .5 | .03685 | 8. | .58961 |
| .6 | .04422 | 9. | .66332 |
| .7 | .05159 | 10. | .73702 |
| .8 | .05896 | 11. | .81072 |
| .9 | .06633 | 12. | .88442 |
| 1. | .07370 | 13. | .96812 |
| 2. | .14740 | 14. | 1.04182 |
| 3. | .22010 | 15. | 1.11525 |
| Ounce measures. | French cubical inches. | English cubical inches. |
| 1 | 1.567 | 1.898 |
| 2 | 3.134 | 3.796 |
| 3 | 4.701 | 5.694 |
| 4 | 6.268 | 7.592 |
| 5 | 7.835 | 9.490 |
| 6 | 9.402 | 11.388 |
| 7 | 10.969 | 13.286 |
| 8 | 12.536 | 15.184 |
| 9 | 14.103 | 17.082 |
| 10 | 15.670 | 18.980 |
| 20 | 31.340 | 37.960 |
| 30 | 47.010 | 56.940 |
| 40 | 62.680 | 75.920 |
| 50 | 78.350 | 94.900 |
| 60 | 94.020 | 113.880 |
| 70 | 109.690 | 132.860 |
| 80 | 125.360 | 151.840 |
| 90 | 141.030 | 170.820 |
| 100 | 156.700 | 189.800 |
| 1000 | 1567.000 | 1898.000 |
| R. | F. | R. | F. | R. | F. | R. | F. | ||||
| 0 | = | 32 | 21 | = | 79.25 | 41 | = | 124.25 | 61 | = | 169.25 |
| 1 | = | 34.25 | 22 | = | 81.5 | 42 | = | 126.5 | 62 | = | 171.5 |
| 2 | = | 36.5 | 23 | = | 83.75 | 43 | = | 128.75 | 63 | = | 173.75 |
| 3 | = | 38.75 | 24 | = | 86 | 44 | = | 131 | 64 | = | 176. |
| 4 | = | 41 | 25 | = | 88.25 | 45 | = | 133.25 | 65 | = | 178.25 |
| 5 | = | 43.25 | 26 | = | 90.5 | 46 | = | 135.5 | 66 | = | 180.5 |
| 6 | = | 45.5 | 27 | = | 92.75 | 47 | = | 137.75 | 67 | = | 182.75 |
| 7 | = | 47.75 | 28 | = | 95 | 48 | = | 140 | 68 | = | 185 |
| 8 | = | 50 | 29 | = | 97.25 | 49 | = | 142.25 | 69 | = | 187.25 |
| 9 | = | 52.25 | 30 | = | 99.5 | 50 | = | 144.5 | 70 | = | 189.5 |
| 10 | = | 54.5 | 31 | = | 101.75 | 51 | = | 146.75 | 71 | = | 191.75 |
| 11 | = | 56.75 | 32 | = | 104 | 52 | = | 149 | 72 | = | 194. |
| 12 | = | 59 | 33 | = | 106.25 | 53 | = | 151.25 | 73 | = | 196.25 |
| 13 | = | 61.25 | 34 | = | 108.5 | 54 | = | 153.5 | 74 | = | 198.5 |
| 14 | = | 63.5 | 35 | = | 110.75 | 55 | = | 155.75 | 75 | = | 200.75 |
| 15 | = | 65.75 | 36 | = | 113 | 56 | = | 158 | 76 | = | 203 |
| 16 | = | 68 | 37 | = | 115.25 | 57 | = | 160.25 | 77 | = | 205.25 |
| 17 | = | 70.25 | 38 | = | 117.5 | 58 | = | 162.5 | 78 | = | 207.5 |
| 18 | = | 72.5 | 39 | = | 119.75 | 59 | = | 164.75 | 79 | = | 209.75 |
| 19 | = | 74.75 | 40 | = | 122 | 60 | = | 167 | 80 | = | 212 |
| 20 | = | 77 |
Note—Any degree, either higher or lower, than what is contained inthe above Table, may be at any time converted, by remembering that onedegree of Reaumeur's scale is equal to 2.25° of Fahrenheit; or it may bedone without the Table by the following formula, R × 9 / 4 + 32 = F;that is, multiply the degree of Reaumeur by 9, divide the product by 4,to the quotient add 32, and the sum is the degree of Fahrenheit.—E.[Pg 485]
The Paris pound, poids de mark of Charlemagne, contains 9216 Parisgrains; it is divided into 16 ounces, each ounce into 8 gros, and eachgros into 72 grains. It is equal to 7561 English Troy grains.
The English Troy pound of 12 ounces contains 5760 English Troy grains,and is equal to 7021 Paris grains.
The English averdupois pound of 16 ounces contains 7000 English Troygrains, and is equal to 8538 Paris grains.
| To reduce Parisgrs. to English Troygrs. divide by | 1.2189 |
| To reduce English Troygrs. to Parisgrs. multiply by | |
| To reduce Paris ounces to English Troy, divide by | 1.015734 |
| To reduce English Troy ounces to Paris, multiply by |
Or the conversion may be made by means of the following Tables.
| The Paris pound | = | 7561 | } |
| The ounce | = | 472.5625 | }English. |
| The gros | = | 59.0703 | }Troy. |
| The grain | = | .8194 | }Grains. |
| The English Troy pound of 12 ounces | = | 7021. | } |
| The Troy ounce | = | 585.0830 | } |
| The dram of 60 grs. | = | 73.1353 | }Paris |
| The penny weight, or denier, of 24 grs. | = | 29.2540 | }grains. |
| The scruple, of 20 grs. | = | 24.3784 | } |
| The averdupois pound of 16 ounces, or 7000 Troy grains. | = | 8538. | } Paris grains. |
| The ounce | = | 533.6250 |
| To reduce Paris feet or inches into English, multiply by | 1.065977 |
| English feet or inches into Paris, divide by | |
| To reduce Paris cubic feet or inches to English, multiply by | 1.211278 |
| English cubic feet or inches to Paris, divide by |
Or by means of the following tables:
| The Paris royal foot of 12 inches | = | 12.7977 | }English |
| The inch | = | 1.0659 | } |
| The line, or 1/12 of an inch | = | .0888 | }inches. |
| The 1/12 of a line | = | .0074 | } |
| The English foot | = | 11.2596 | } |
| The inch | = | .9383 | } |
| The 1/8 of an inch | = | .1173 | }Paris inches. |
| The 1/10 | = | .0938 | } |
| The line, or 1/12 | = | .0782 | } |
| The Paris cube foot | = | 1.211278 | } | English cubical feet, or | {2093.088384 | } | inches. |
| The cubic inch | = | .000700 | } | {1.211278 | } |
| The English cube foot, or 1728 cubical inches | = | 1427.4864 | }French |
| The cubical inch | = | .8260 | }cubical |
| The cube tenth | = | .0008 | }inches. |
The Paris pint contains 58.145[63] English cubical inches, and theEnglish wine pint contains 28.85 cubical inches; or, the Paris pintcontains[Pg 489] 2.01508 English pints, and the English pint contains .49617Paris pints; hence,
| To reduce the Paris pint to the English, multiply by | 2.01508. |
| To reduce the English pint to the Paris, divide by |
| Names of the Gasses. | Weight of a cubical inch. | Weight of a cubical foot. | ||
| (A) | qrs. | oz. | dr. | qrs. |
| Atmospheric air | .32112 | 1 | 1 | 15 |
| Azotic gas | .30064 | 1 | 0 | 39.5 |
| Oxygen gas | .34211 | 1 | 1 | 51 |
| Hydrogen gas | .02394 | 0 | 0 | 41.26 |
| Carbonic acid gas | .44108 | 1 | 4 | 41 |
| (B) | ||||
| Nitrous gas | .37000 | 1 | 2 | 39 |
| Ammoniacal gas | .18515 | 0 | 5 | 19.73 |
| Sulphurous acid gas | .71580 | 2 | 4 | 38 |
[Note A: These five were ascertained by Mr Lavoisier himself.—E.]
[Note B: The last three are inserted by Mr Lavoisier upon the authorityof Mr Kirwan.—E.][Pg 491]
| Pure gold of 24 carats melted but not hammered | 19.2581 |
| The same hammered | 19.3617 |
| Gold of the Parisian standard, 22 carats fine, not hammered(A) | 17.4863 |
| The same hammered | 17.5894 |
| Gold of the standard of French coin, 21-22/32 carats fine, not hammered | 17.4022 |
| The same coined | 17.6474 |
| Gold of the French trinket standard, 20 carats fine, not hammered | 15.7090 |
| The same hammered | 15.7746 |
[Note A: The same with Sterling.]
| Pure or virgin silver, 24 deniers, not hammered | 10.4743 |
| The same hammered | 10.5107 |
| Silver of the Paris standard, 11 deniers 10 grains fine, not hammered(B) | 10.1752 |
| The same hammered | 10.3765 |
| [Pg 492] | |
| Silver, standard of French coin, 10 deniers 21 grains fine, not hammered | 10.0476 |
| The same coined | 10.4077 |
[Note B: This is 10grs. finer than Sterling.]
| Crude platina in grains | 15.6017 |
| The same, after being treated with muriatic acid | 16.7521 |
| Purified platina, not hammered | 19.5000 |
| The same hammered | 20.3366 |
| The same drawn into wire | 21.0417 |
| The same passed through rollers | 22.0690 |
| Copper, not hammered | 7.7880 |
| The same wire drawn | 8.8785 |
| Brass, not hammered | 8.3958 |
| The same wire drawn | 8.5441 |
| Cast iron | 7.2070 |
| Bar iron, either screwed or not | 7.7880 |
| Steel neither tempered nor screwed | 7.8331 |
| Steel screwed but not tempered | 7.8404 |
| Steel tempered and screwed | 7.8180 |
| Steel tempered and not screwed | 7.8163 |
| [Pg 493] |
| Pure tin from Cornwall melted and not screwed | 7.2914 |
| The same screwed | 7.2994 |
| Malacca tin, not screwed | 7.2963 |
| The same screwed | 7.3065 |
| Molten lead | 11.3523 |
| Molten zinc | 7.1908 |
| Molten bismuth | 9.8227 |
| Molten cobalt | 7.8119 |
| Molten arsenic | 5.7633 |
| Molten nickel | 7.8070 |
| Molten antimony | 6.7021 |
| Crude antimony | 4.0643 |
| Glass of antimony | 4.9464 |
| Molybdena | 4.7385 |
| Tungstein | 6.0665 |
| Mercury | 13.5681 |
| White Oriental diamond | 3.5212 |
| Rose-coloured Oriental ditto | 3.5310 |
| Oriental ruby | 4.2833 |
| Spinell ditto | 3.7600 |
| Ballas ditto | 3.6458 |
| Brasillian ditto | 3.5311 |
| Oriental topas | 4.0106 |
| [Pg 494] | |
| Ditto Pistachio ditto | 4.0615 |
| Brasillian ditto | 3.5365 |
| Saxon topas | 3.5640 |
| Ditto white ditto | 3.5535 |
| Oriental saphir | 3.9941 |
| Ditto white ditto | 3.9911 |
| Saphir of Puy | 4.0769 |
| Ditto of Brasil | 3.1307 |
| Girasol | 4.0000 |
| Ceylon jargon | 4.4161 |
| Hyacinth | 3.6873 |
| Vermillion | 4.2299 |
| Bohemian garnet | 4.1888 |
| Dodecahedral ditto | 4.0627 |
| Syrian ditto | 4.0000 |
| Volcanic ditto, with 24 sides | 2.4684 |
| Peruvian emerald | 2.7755 |
| Crysolite of the jewellers | 2.7821 |
| Ditto of Brasil | 2.6923 |
| Beryl, or Oriental aqua marine | 3.5489 |
| Occidental aqua marine | 2.7227 |
| Pure rock cristal of Madagascar | 2.6530 |
| Ditto of Brasil | 2.6526 |
| Ditto of Europe, or gelatinous | 2.6548 |
| Cristallized quartz | 2.6546 |
| Amorphous ditto | 2.6471 |
| [Pg 495] | |
| Oriental agate | 2.5901 |
| Agate onyx | 2.6375 |
| Transparent calcedony | 2.6640 |
| Carnelian | 2.6137 |
| Sardonyx | 2.6025 |
| Prase | 2.5805 |
| Onyx pebble | 2.6644 |
| Pebble of Rennes | 2.6538 |
| White jade | 2.9502 |
| Green jade | 2.9660 |
| Red jasper | 2.6612 |
| Brown ditto | 2.6911 |
| Yellow ditto | 2.7101 |
| Violet ditto | 2.7111 |
| Gray ditto | 2.7640 |
| Jasponyx | 2.8160 |
| Black prismatic hexahedral schorl | 3.3852 |
| Black spary ditto | 3.3852 |
| Black amorphous schorl, called antique basaltes | 2.9225 |
| Paving stone | 2.4158 |
| Grind stone | 2.1429 |
| Cutler's stone | 2.1113 |
| Fountainbleau stone | 2.5616 |
| Scyth stone of Auvergne | 2.5638 |
| Ditto of Lorrain | 2.5298 |
| Mill stone | 2.4835 |
| White flint | 2.5941 |
| Blackish ditto | 2.5817 |
| [Pg 496] |
| Opake green Italian serpentine, or gabro of the Florentines | 2.4295 | |
| Coarse Briancon chalk | 2.7274 | |
| Spanish chalk | 2.7902 | |
| Foliated lapis ollaris of Dauphiny | 2.7687 | |
| Ditto ditto from Sweden | 2.8531 | |
| Muscovy talc | 2.7917 | |
| Black mica | 2.9004 | |
| Common schistus or slate | 2.6718 | |
| New slate | 2.8535 | |
| White rasor hone | 2.8763 | |
| Black and white hone | 3.1311 | |
| Rhombic or Iceland cristal | 2.7151 | |
| Pyramidal calcareous spar | 2.7141 | |
| Oriental or white antique alabaster | 2.7302 | |
| Green Campan marble | 2.7417 | |
| Red Campan marble | 2.7242 | |
| White Carara marble | 2.7168 | |
| White Parian marble | 2.8376 | |
| Various kinds of calcareous stones | }from | 1.3864 |
| used in France for building. | }to | 2.3902 |
| Heavy spar | 4.4300 | |
| White fluor | 3.1555 | |
| Red ditto | 3.1911 | |
| Green ditto | 3.1817 | |
| Blue ditto | 3.1688 | |
| Violet ditto | 3.1757 | |
| [Pg 497] | ||
| Red scintilant zeolite from Edelfors | 2.4868 | |
| White scintilant zeolite | 2.0739 | |
| Cristallized zeolite | 2.0833 | |
| Black pitch stone | 2.0499 | |
| Yellow pitch stone | 2.0860 | |
| Red ditto | 2.6695 | |
| Blackish ditto | 2.3191 | |
| Red porphyry | 2.7651 | |
| Ditto of Dauphiny | 2.7033 | |
| Green serpentine | 2.8960 | |
| Black ditto of Dauphiny, called variolite | 2.9339 | |
| Green ditto from Dauphiny | 2.9883 | |
| Ophites | 2.9722 | |
| Granitello | 3.0626 | |
| Red Egyptian granite | 2.6541 | |
| Beautiful red granite | 2.7609 | |
| Granite of Girardmas | 2.7163 | |
| Pumice stone | .9145 | |
| Lapis obsidianus | 2.3480 | |
| Pierre de Volvic | 2.3205 | |
| Touch stone | 2.4153 | |
| Basaltes from Giants Causeway | 2.8642 | |
| Ditto prismatic from Auvergne | 2.4153 | |
| Glass gall | 2.8548 | |
| Bottle glass | 2.7325 | |
| Green glass | 2.6423 | |
| White glass | 2.8922 | |
| St Gobin cristal | 2.4882 | |
| Flint glass | 3.3293 | |
| Borax glass | 2.6070 | |
| [Pg 498] | ||
| Seves porcelain | 2.1457 | |
| Limoges ditto | 2.3410 | |
| China ditto | 2.3847 | |
| Native sulphur | 2.0332 | |
| Melted sulphur | 1.9907 | |
| Hard peat | 1.3290 | |
| Ambergrease | .9263 | |
| Yellow transparent amber | 1.0780 |
| Distilled water | 1.0000 | |||
| Rain water | 1.0000 | |||
| Filtered water of the Seine | 1.00015 | |||
| Arcueil water | 1.00046 | |||
| Avray water | 1.00043 | |||
| Sea water | 1.0263 | |||
| Water of the Dead Sea | 1.2403 | |||
| Burgundy wine | .9915 | |||
| Bourdeaux ditto | .9939 | |||
| Malmsey Madeira | 1.0382 | |||
| Red beer | 1.0338 | |||
| White ditto | 1.0231 | |||
| Cyder | 1.0181 | |||
| Highly rectified alkohol | .8293 | |||
| Common spirits of wine | .8371 | |||
| [Pg 499] | ||||
| Alkohol | 15 pts. | water | 1 part. | .8527 |
| 14 | 2 | .8674 | ||
| 13 | 3 | .8815 | ||
| 12 | 4 | .8947 | ||
| 11 | 5 | .9075 | ||
| 10 | 6 | .9199 | ||
| 9 | 7 | .9317 | ||
| 8 | 8 | .9427 | ||
| 7 | 9 | .9519 | ||
| 6 | 10 | .9594 | ||
| 5 | 11 | .9674 | ||
| 4 | 12 | .9733 | ||
| 3 | 13 | .9791 | ||
| 2 | 14 | .9852 | ||
| 1 | 15 | .9919 | ||
| Sulphuric ether | .7394 | |||
| Nitric ether | .9088 | |||
| Muriatic ether | .7298 | |||
| Acetic ether | .8664 | |||
| Sulphuric acid | 1.8409 | |||
| Nitric ditto | 1.2715 | |||
| Muriatic ditto | 1.1940 | |||
| Red acetous ditto | 1.0251 | |||
| White acetous ditto | 1.0135 | |||
| Distilled ditto ditto | 1.0095 | |||
| Acetic ditto | 1.0626 | |||
| Formic ditto | .9942 | |||
| Solution of caustic ammoniac, | or volatil alkali fluor | .8970 | ||
| [Pg 500] | ||||
| Essential or volatile oil | of turpentine | .8697 | ||
| Liquid turpentine | .9910 | |||
| Volatile oil of lavender | .8938 | |||
| Volatile oil of cloves | 1.0363 | |||
| Volatile oil of cinnamon | 1.0439 | |||
| Oil of olives | .9153 | |||
| Oil of sweet almonds | .9170 | |||
| Lintseed oil | .9403 | |||
| Oil of poppy seed | .9288 | |||
| Oil of beech mast | .9176 | |||
| Whale oil | .9233 | |||
| Womans milk | 1.0203 | |||
| Mares milk | 1.0346 | |||
| Ass milk | 1.0355 | |||
| Goats milk | 1.0341 | |||
| Ewe milk | 1.0409 | |||
| Cows milk | 1.0324 | |||
| Cow whey | 1.0193 | |||
| Human urine | 1.0106 |
| Common yellow or white rosin | 1.0727 |
| Arcanson | 1.0857 |
| Galipot(A) | 1.0819 |
| Baras(A) | 1.0441 |
| [Pg 501] | |
| Sandarac | 1.0920 |
| Mastic | 1.0742 |
| Storax | 1.1098 |
| Opake copal | 1.1398 |
| Transparent ditto | 1.0452 |
| Madagascar ditto | 1.0600 |
| Chinese ditto | 1.0628 |
| Elemi | 1.0182 |
| Oriental anime | 1.0284 |
| Occidental ditto | 1.0426 |
| Labdanum | 1.1862 |
| Dittoin tortis | 2.4933 |
| Resin of guaiac | 1.2289 |
| Ditto of jallap | 1.2185 |
| Dragons blood | 1.2045 |
| Gum lac | 1.1390 |
| Tacamahaca | 1.0463 |
| Benzoin | 1.0924 |
| Alouchi(B) | 1.0604 |
| Caragna(C) | 1.1244 |
| Elastic gum | .9335 |
| Camphor | .9887 |
| Gum ammoniac | 1.2071 |
| Sagapenum | 1.2008 |
| [Pg 502] | |
| Ivy gum(D) | 1.2948 |
| Gamboge | 1.2216 |
| Euphorbium | 1.1244 |
| Olibanum | 1.1732 |
| Myrrh | 1.3600 |
| Bdellium | 1.3717 |
| Aleppo Scamony | 1.2354 |
| Smyrna ditto | 1.2743 |
| Galbanum | 1.2120 |
| Assafoetida | 1.3275 |
| Sarcocolla | 1.2684 |
| Opoponax | 1.6226 |
| Cherry tree gum | 1.4817 |
| Gum Arabic | 1.4523 |
| Tragacanth | 1.3161 |
| Basora gum | 1.4346 |
| Acajou gum(E) | 1.4456 |
| Monbain gum(F) | 1.4206 |
| Inspissated juice of liquorice | 1.7228 |
| —— Acacia | 1.5153 |
| —— Areca | 1.4573 |
| Terra Japonica | 1.3980 |
| Hepatic aloes | 1.3586 |
| Socotrine aloes | 1.3795 |
| Inspissated juice of St John's wort | 1.5263 |
| [Pg 503] | |
| Opium | 1.3366 |
| Indigo | .7690 |
| Arnotto | .5956 |
| Yellow wax | .9648 |
| White ditto | .9686 |
| Ouarouchi ditto(G) | .8970 |
| Cacao butter | .8916 |
| Spermaceti | .9433 |
| Beef fat | .9232 |
| Veal fat | .9342 |
| Mutton fat | .9235 |
| Tallow | .9419 |
| Hoggs fat | .9368 |
| Lard | .9478 |
| Butter | .9423 |
[Note A: Resinous juices extracted in France from the Pine.VideBomare's Dict.]
[Note B: Odoriferous gum from the tree which produces the CortexWinteranus.Bomare.]
[Note C: Resin of the tree called in Mexico Caragna, or Tree of Madness.Ibid.]
[Note D: Extracted in Persia and the warm countries from Hederaterrestris.—Bomare.]
[Note E: From a Brasilian tree of this name.—Ibid.]
[Note F: From a tree of this name.—Ibid.]
[Note G: The produce of the Tallow Tree of Guayana.Vide Bomare'sDict.]
| Heart of oak 60 years old | 1.1700 |
| Cork | .2400 |
| Elm trunk | .6710 |
| Ash ditto | .8450 |
| Beech | .8520 |
| Alder | .8000 |
| Maple | .7550 |
| Walnut | .6710 |
| Willow | .5850 |
| Linden | .6040 |
| [Pg 504] | |
| Male fir | .5500 |
| Female ditto | .4980 |
| Poplar | .3830 |
| White Spanish ditto | .5294 |
| Apple tree | .7930 |
| Pear tree | .6610 |
| Quince tree | .7050 |
| Medlar | .9440 |
| Plumb tree | .7850 |
| Olive wood | .9270 |
| Cherry tree | .7150 |
| Filbert tree | .6000 |
| French box | .9120 |
| Dutch ditto | 1.3280 |
| Dutch yew | .7880 |
| Spanish ditto | .8070 |
| Spanish cypress | .6440 |
| American cedar | .5608 |
| Pomgranate tree | 1.3540 |
| Spanish mulberry tree | .8970 |
| Lignum vitae | 1.3330 |
| Orange tree | .7050 |
Note—The numbers in the above Table, if the Decimal point be carriedthree figures farther to the right hand, nearly express the absoluteweight of an English cube foot of each substance in averdupois ounces.See No. VIII. of the Appendix.—E.[Pg 505]
Rulesfor Calculating the Absolute Gravity in English Troy Weight of aCubic Foot and Inch, English Measure, of any Substance whose SpecificGravity is known[64].
In 1696, Mr Everard, balance-maker to the Exchequer, weighed before theCommissioners of the House of Commons 2145.6 cubical inches, by theExchequer standard foot, of distilled water, at the temperature of 55°of Fahrenheit, and found it to weigh 1131 oz. 14 dts. Troy, of theExchequer standard. The beam turned with 6 grs. when loaded with 30pounds in each scale. Hence, supposing the pound averdupois to weigh7000 grs. Troy, a cubic foot of water weighs 62-1/2 pounds averdupois,or 1000 ounces averdupois, wanting 106 grains Troy. And hence, if thespecific gravity of water be called 1000, the proportional specificgravities of all other bodies will nearly express the number ofaverdupois ounces in a cubic foot. Or more accurately, supposing thespecific gravity of water expressed by 1. and of all other bodies inproportional numbers, as the[Pg 506] cubic foot of water weighs, at the abovetemperature, exactly 437489.4 grains Troy, and the cubic inch of water253.175 grains, the absolute weight of a cubical foot or inch of anybody in Troy grains may be found by multiplying their specific gravityby either of the above numbers respectively.
By Everard's experiment, and the proportions of the English and Frenchfoot, as established by the Royal Society and French Academy ofSciences, the following numbers are ascertained.
| Paris grains in a Paris cube foot of water | = | 645511 |
| English grains in a Paris cube foot of water | = | 529922 |
| Paris grains in an English cube foot of water | = | 533247 |
| English grains in an English cube foot of water | = | 437489.4 |
| English grains in an English cube inch of water | = | 253.175 |
| By an experiment of Picard with the measure and | ||
| weight of the Chatelet, the Paris cube foot of | ||
| water contains of Paris grains | = | 641326 |
| By one of Du Hamel, made with great care | = | 641376 |
| By Homberg | = | 641666 |
These show some uncertainty in measures or in weights; but the abovecomputation from Everard's experiment may be relied on, because thecomparison of the foot of England with that of France was made by thejoint labours of the Royal Society of London and the French Academy ofSciences: It agrees likewise very nearly with the weight assigned by MrLavoisier, 70 Paris pounds to the cubical foot of water.[Pg 508]
| Grains | = Pound. |
| 1 | .0001736 |
| 2 | .0003472 |
| 3 | .0005208 |
| 4 | .0006944 |
| 5 | .0008681 |
| 6 | .0010417 |
| 7 | .0012153 |
| 8 | .0013889 |
| 9 | .0015625 |
| 10 | .0017361 |
| 20 | .0034722 |
| 30 | .0052083 |
| 40 | .0069444 |
| 50 | .0086806 |
| 60 | .0104167 |
| 70 | .0121528 |
| 80 | .0138889 |
| 90 | .0156250 |
| 100 | .0173611 |
| 200 | .0374222 |
| 300 | .0520833 |
| 400 | .0694444 |
| 500 | .0868055 |
| 600 | .1041666 |
| 700 | .1215277 |
| 800 | .1388888 |
| 900 | .1562499 |
| 1000 | .1736110 |
| 2000 | .3472220 |
| 3000 | .5208330 |
| 4000 | .6944440 |
| 5000 | .8680550 |
| 6000 | 1.0418660 |
| 7000 | 1.2152770 |
| 8000 | 1.3888880 |
| 9000 | 1.5624990 |
| Drams | = Pound. |
| 1 | .0104167 |
| 2 | .0208333 |
| 3 | .0312500 |
| 4 | .0416667 |
| 5 | .0520833 |
| 6 | .0625000 |
| 7 | .0729167 |
| 8 | .0833333 |
| Ounces | = Pounds. |
| 1 | .0833333 |
| 2 | .1666667 |
| 3 | .2500000 |
| 4 | .3333333 |
| 5 | .4166667 |
| 6 | .5000000 |
| 7 | .5833333 |
| 8 | .6666667 |
| 9 | .7500000 |
| 10 | .8333333 |
| 11 | .9166667 |
| 12 | 1.0000000 |
| Tenth parts. | |||
| lib. = | oz. | dr. | gr. |
| 0.1 | 1 | 1 | 36 |
| 0.2 | 2 | 3 | 12 |
| 0.3 | 3 | 4 | 48 |
| 0.4 | 4 | 6 | 24 |
| 0.5 | 6 | 0 | 0 |
| 0.6 | 7 | 1 | 36 |
| 0.7 | 8 | 3 | 12 |
| 0.8 | 9 | 4 | 48 |
| 0.9 | 10 | 6 | 24 |
| Hundredth parts. | |||
| 0.01 | 0 | 0 | 57.6 |
| 0.02 | 0 | 1 | 55.2 |
| 0.03 | 0 | 2 | 52.8 |
| 0.04 | 0 | 3 | 50.4 |
| 0.05 | 0 | 4 | 48.0 |
| 0.06 | 0 | 5 | 45.6 |
| 0.07 | 0 | 6 | 43.2 |
| 0.08 | 0 | 7 | 40.8 |
| 0.09 | 0 | 3 | 38.4 |
| Thousandths. | |||
| 0.001 | 0 | 0 | 5.76 |
| 0.002 | 0 | 0 | 11.52 |
| 0.003 | 0 | 0 | 17.28 |
| 0.004 | 0 | 0 | 23.04 |
| 0.005 | 0 | 0 | 28.80 |
| lib. = | grs. | ||
| 0.006 | 34.56 | ||
| 0.007 | 40.32 | ||
| 0.008 | 46.08 | ||
| 0.009 | 51.84 | ||
| Ten thousandth parts. | |||
| 0.0001 | 0.576 | ||
| 0.0002 | 1.152 | ||
| 0.0003 | 1.728 | ||
| 0.0004 | 2.304 | ||
| 0.0005 | 2.880 | ||
| 0.0006 | 3.456 | ||
| 0.0007 | 4.032 | ||
| 0.0008 | 4.608 | ||
| 0.0009 | 5.184 | ||
| Hundred thousandth parts. | |||
| 0.00001 | 0.052 | ||
| 0.00002 | 0.115 | ||
| 0.00003 | 0.173 | ||
| 0.00004 | 0.230 | ||
| 0.00005 | 0.288 | ||
| 0.00006 | 0.346 | ||
| 0.00007 | 0.403 | ||
| 0.00008 | 0.461 | ||
| 0.00009 | 0.518 | ||
Tableof the English Cubical Inches and Decimals corresponding to adeterminate Troy Weight of Distilled Water at the Temperature of 55°,calculated from Everard's experiment.
| Grs. | Cubical inches. |
| 1 = | .0039 |
| 2 | .0078 |
| 3 | .0118 |
| 4 | .0157 |
| 5 | .0197 |
| 6 | .0236 |
| 7 | .0275 |
| 8 | .0315 |
| 9 | .0354 |
| 10 | .0394 |
| 20 | .0788 |
| 30 | .1182 |
| 40 | .1577 |
| 50 | .1971 |
| Drams. | Cubical inches. |
| 1 = | .2365 |
| 2 | .4731 |
| 3 | .7094 |
| 4 | .9463 |
| 5 | 1.1829 |
| 6 | 1.4195 |
| 7 | 1.6561 |
| Oz. | Cubical inches. |
| 1 = | 1.8927 |
| 2 | 3.7855 |
| 3 | 5.6782 |
| 4 | 7.5710 |
| 5 | 9.4631 |
| 6 | 11.3565 |
| 7 | 13.2493 |
| 8 | 15.1420 |
| 9 | 17.0748 |
| 10 | 18.9276 |
| 11 | 20.8204 |
| Libs. | Cubical inches. |
| 1 = | 22.7131 |
| 2 | 45.4263 |
| 3 | 68.1394 |
| 4 | 90.8525 |
| 5 | 113.5657 |
| 6 | 136.2788 |
| 7 | 158.9919 |
| 8 | 181.7051 |
| 9 | 204.4183 |
| 10 | 227.1314 |
| 50 | 1135.6574 |
| 100 | 2271.3148 |
| 1000 | 22713.1488 |
[62] For the materials of this Article the Translator isindebted to Professor Robertson.
[63] It is said,Belidor Archit. Hydrog. to contain 31oz.64grs. of water, which makes it 58.075 English inches; but, as thereis considerable uncertainty in the determinations of the weight of theFrench cubical measure of water, owing to the uncertainty of thestandards made use of, it is better to abide by Mr Everard's measure,which was with the Exchequer standards, and by the proportions of theEnglish and French foot, as established by the French Academy and RoyalSociety.
[64] The whole of this and the following article wascommunicated to the Translator by Professor Robinson.—E.
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