| Niter | |
|---|---|
.jpg) A piece of niter collected in Tarapaca, Chile | |
| General | |
| Category | Nitrates,oxide mineral |
| Formula | KNO3 |
| IMA symbol | Nit[1] |
| Strunz classification | 5.NA.10 |
| Dana classification | 18.1.2.1 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Cmc21 |
| Identification | |
| Color | White |
| Crystal habit | Druse oracicular |
| Cleavage | Very good on {001}; good on {010} |
| Fracture | Brittle |
| Mohs scale hardness | 2 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Specific gravity | 2.10 (calc.) |
| Solubility | Soluble |
| References | [2][3][4] |
Niter ornitre[5] is the mineral form ofpotassium nitrate, KNO3. It is a soft, white, highly soluble mineral found primarily in arid climates or cave deposits.
Potassium and other nitrates are of great importance for use infertilizers and, historically,gunpowder. Much of the world's demand is now met by synthetically produced nitrates, though the natural mineral is still mined and is still of significant commercial value.[6][7]
Historically, the termniter was not well differentiated fromnatron, both of which have been very vaguely defined but generally refer to compounds ofsodium orpotassium combined withcarbonate ornitrate ions.
Niter is a colorless to white mineral crystallizing in theorthorhombiccrystal system. It is the mineral form ofpotassium nitrate,KNO3,[8] and is soft (Mohs hardness 2),[9] highly soluble in water,[8] and easily fusible. Its crystal structure resembles that ofaragonite, with potassium replacing calcium and nitrate replacing carbonate.[10] It occurs in the soils of arid regions and as massive encrustations andefflorescent growths oncavern walls and ceilings where solutions containingalkali potassium and nitrate seep into the openings.[8] It occasionally occurs as prismaticacicular crystal groups, and individual crystals commonly show pseudohexagonaltwinning on [110]. Niter and other nitrates can also form in association with deposits ofguano and similar organic materials.[9]
Niter as a term has been known since ancient times, although there is much historical confusion withnatron (an impure sodium carbonate/bicarbonate), and not all of the ancient salts known by this name or similar names in the ancient world contained nitrate.[8] The name is from theAncient Greekνιτρωνnitron fromAncient Egyptiannetjeri, related to theHebrewnéter, for salt-derived ashes (their interrelationship is not clear).[11]
The Hebrewnéter may have been used as, or in conjunction, withsoap, as implied byJeremiah 2:22, "For though thou wash thee with niter, and take thee much soap..." However, it is not certain which substance (or substances) the Biblical "neter" refers to, with some suggestingsodium carbonate.[12]
TheNeo-Latin word forsodium,natrium, is derived from this same class of desert minerals callednatron (French)[13] through Spanishnatrón from Greekνίτρον (nitron), derived from Ancient Egyptiannetjeri, referring to the sodium carbonate salts occurring in the deserts of Egypt, not thenitratine (nitrated sodium salts) typically occurring in the deserts ofChile (classically known as "Chilean saltpeter" and variants of this term).[11][14][self-published source?]
A term (ἀφρόνιτρον,aphronitron oraphronitre) which translates as "foam of niter" was a regular purchase in a fourth-century AD series of financial accounts, and since it was expressed as being "for the baths" was probably used as soap.[15]
Niter was used to refer specifically to nitrated salts known as various types ofsaltpeter (only nitrated salts were good for making gunpowder) by the time niter and its derivativenitric acid were first used to name the elementnitrogen, in 1790.[16]
Because of its ready solubility in water, niter is most often found in arid environments and often in conjunction with other soluble minerals likehalides,iodates,borates,gypsum, and rarer carbonates and sulphates.[17][18]
Niter occurs naturally in certain places like the "Caves of Salnitre" (Collbató) known since the Neolithic. In the "Cova del Rat Penat",guano (bat excrements) deposited over thousands of years became saltpeter after beingleached by the action of rainwater.[citation needed]
In 1783,Giuseppe Maria Giovene andAlberto Fortis together discovered a "natural nitrary" in adoline close toMolfetta, Italy, namedPulo di Molfetta. The two scientists discovered that niter formed inside the walls of the caves of the doline, under certain conditions of humidity and temperature.[19] After the discovery, it was suggested that manure could be used for agriculture, in order to increase the production, rather than to make gunpowder.[20] The discovery was challenged by scholars until chemistGiuseppe Vairo and his pupilAntonio Pitaro confirmed the discovery. Naturalists sent by academies from all Europe came in large number to visit the site; since niter is a fundamental ingredient in the production of gunpowder, these deposits were of considerable strategic interest.[21]: 8–10 The government started extraction. Shortly thereafter, Giovene discovered niter in other caves ofApulia.[21]: 9–10 [22] The remnants of the extraction plant is a site ofindustrial archaeology, although currently not open to tourists.[23]
Related minerals are soda niter (sodium nitrate), ammonia niter orgwihabaite (ammonium nitrate), nitrostrontianite (strontium nitrate), nitrocalcite (calcium nitrate), nitromagnesite (magnesium nitrate), nitrobarite (barium nitrate) and two copper nitrates,gerhardtite and buttgenbachite; in fact all of the natural elements in the first three columns of theperiodic table and numerous other cations form nitrates which are uncommonly found for the reasons given, but have been described. Niter was used to refer specifically to nitrated salts known asvarious types of saltpeter (only nitrated salts were good for makinggunpowder) by the time niter and its derivativenitric acid were first used to name the elementnitrogen, in 1790.[citation needed]
