 | |
 | |
| Names | |
|---|---|
| IUPAC name Silver(I) chloride | |
| Other names | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
|
| ECHA InfoCard | 100.029.121 |
| RTECS number |
|
| UNII | |
| |
| |
| Properties | |
| AgCl | |
| Molar mass | 143.32 g·mol−1 |
| Appearance | White solid |
| Density | 5.56 g cm−3 |
| Melting point | 455 °C (851 °F; 728 K) |
| Boiling point | 1,547 °C (2,817 °F; 1,820 K) |
| 520 μg/100 g at 50 °C | |
Solubility product (Ksp) | 1.77×10−10[1] |
| Solubility | soluble inNH3, conc.HCl, conc.H2SO4, alkalicyanide,(NH4)2CO3,KBr,Na2S2O3; |
| −49.0·10−6 cm3/mol | |
Refractive index (nD) | 2.071 |
| Structure[2] | |
| cubic | |
| Fm3m (No. 225) | |
a = 555pm | |
| Octahedral | |
| Thermochemistry | |
Std molar entropy(S⦵298) | 96 J·mol−1·K−1[3] |
Std enthalpy of formation(ΔfH⦵298) | −127 kJ·mol−1[3] |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Safety data sheet (SDS) | Fischer Scientific,Salt Lake Metals |
| Related compounds | |
Otheranions | silver(I) fluoride,silver bromide,silver iodide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Silver chloride is aninorganic chemical compound with thechemical formulaAgCl. This whitecrystalline solid is well known for its lowsolubility inwater and itssensitivity to light. Upon illumination orheating, silver chloride converts to silver (andchlorine), which is signaled by grey to black or purplish coloration in some samples. AgCl occurs naturally as the mineralchlorargyrite.
It is produced by ametathesis reaction for use inphotography and inpH meters aselectrodes.
Silver chloride is unusual in that, unlike mostchloride salts, it has very low solubility. It is easily synthesized bymetathesis: combining anaqueous solution ofsilver nitrate (which is soluble) with a soluble chloride salt, such assodium chloride (which is used industrially as a method of producing AgCl), orcobalt(II) chloride. The silver chloride that forms will precipitate immediately.[3][4]: 46
It can also be produced by the reaction of silver metal andaqua regia; however, the insolubility of silver chloride decelerates the reaction. Silver chloride is also aby-product of theMiller process, where silver metal is reacted with chlorine gas at elevated temperatures.[4]: 21 [5]
Silver chloride has been known since ancient times.Ancient Egyptians produced it as a method of refining silver, which was done by roasting silver ores with salt to produce silver chloride, which was subsequently decomposed to silver and chlorine.[4]: 19 However, it was later identified as a distinct compound of silver in 1565 byGeorg Fabricius.[6][7] Silver chloride, historically known asluna cornea (which could be translated as "horn silver" as the moonwas an alchemic codename for silver),[7] has also been an intermediate in other historical silver refining processes. One such example is theAugustin process developed in 1843, wherein copper ore containing small amounts of silver is roasted in chloridizing conditions and the silver chloride produced is leached bybrine, where it is more soluble.[4]: 32
Silver-based photographic films were first made in 1727 byJohann Heinrich Schulze withsilver nitrate. However, he was not successful in making permanent images, as they faded away.[8] Later in 1816, the use of silver chloride was introduced into photography byNicéphore Niépce.[4]: 38–39 [9]
The solid adopts thefccNaCl structure, in which each Ag+ ion is surrounded by anoctahedron of six chloride ligands.AgF andAgBr crystallize similarly.[10] However, the crystallography depends on the condition of crystallization, primarily free silver ion concentration, as is shown in the picture to the left (greyish tint and metalliclustre are due to partiallyreducedsilver).[11]
Above 7.5GPa, silver chloride transitions into amonoclinic KOH phase. Then at 11 GPa, it undergoes another phase change to anorthorhombicTlI phase.[2]
AgCl dissolves in solutions containingligands such aschloride,cyanide,triphenylphosphine,thiosulfate,thiocyanate andammonia. Silver chloride reacts with these ligands according to the following illustrative equations:[4]: 25–33
Of these reactions used to leach silver chloride from silver ores, cyanidation is the most commonly used. Cyanidation produces the solubledicyanoargentate complex, which is later turned back to silver by reduction.[4]: 26
Silver chloride does not react with nitric acid, but instead reacts with sulfuric acid to producesilver sulfate.[12] Then the sulfate is protonated in the presence of sulfuric acid tobisulfate, which can be reversed by dilution. This reaction is used to separate silver from other platinum group metals.[4]: 42
Most complexes derived from AgCl are two-, three-, and, in rare cases, four-coordinate, adopting linear, trigonal planar, and tetrahedral coordination geometries, respectively.[13]
These two reactions are particularly important in thequalitative analysis of AgCl in labs as AgCl is white, which changes toAg3AsO3 (silver arsenite) which is yellow, orAg3AsO4 (silver arsenate) which is reddish brown.[13]
In one of the most famous reactions in chemistry, the addition of colorless aqueoussilver nitrate to an equally colorless solution of sodium chloride produces an opaque white precipitate of AgCl:[14]
This conversion is a common test for the presence ofchloride in solution. Due to its conspicuousness, it is easily used in titration, which gives the typical case ofargentometry.[12]
Thesolubility product,Ksp, for AgCl in water is1.77×10−10 at room temperature, which indicates that only 1.9 mg (that is,) of AgCl will dissolve per liter of water.[1] The chloride content of an aqueous solution can be determined quantitatively by weighing the precipitated AgCl, which conveniently is non-hygroscopic since AgCl is one of the few transition metal chlorides that are insoluble in water. Interfering ions for this test are bromide and iodide, as well as a variety of ligands (seesilver halide).
For AgBr and AgI, theKsp values are 5.2 x 10−13 and 8.3 x 10−17, respectively.Silver bromide (slightly yellowish white) andsilver iodide (bright yellow) are also significantly more photosensitive than is AgCl.[1][4]: 46
AgCl quickly darkens on exposure to light by disintegrating into elementalchlorine and metallicsilver. This reaction is used in photography and film and is the following:[5]
The process is not reversible because the silver atom liberated is typically found at acrystal defect or an impurity site so that the electron's energy is lowered enough that it is "trapped".[5]
Silver chloride is a constituent of thesilver chloride electrode which is a common reference electrode inelectrochemistry. The electrode functions as a reversibleredox electrode and the equilibrium is between the solidsilver metal and silver chloride in a chloride solution of a given concentration. It is usually the internal reference electrode inpH meters and it is often used as a reference inreduction potential measurements. As an example of the latter, the silver chloride electrode is the most commonly used reference electrode for testingcathodic protectioncorrosion control systems inseawater environments.[15]
Silver chloride and silver nitrate have been used inphotography since it began, and are well known for their light sensitivity.[6] It was also a vital part of theDaguerreotype sensitization where silver plates were fumed with chlorine to produce a thin layer of silver chloride.[16] Another famous process that used silver chloride was thegelatin silver process where embedded silver chloride crystals ingelatin were used to produce images.[17] However, with advances incolor photography, these methods of black-and-white photography have dwindled. Even though color photography uses silver chloride, it only works as a mediator for transforming light into organic image dyes.[18]
Other photographic uses include makingphotographic paper, since it reacts with photons to formlatent images via photoreduction; and inphotochromic lenses, taking advantage of its reversible conversion to Ag metal. Unlike photography, where the photoreduction is irreversible, the glass prevents the electron from being 'trapped'.[19] These photochromic lenses are used primarily insunglasses.[4]
Silver chloride nanoparticles are widely sold commercially as anantimicrobial agent.[12][20] The antimicrobial activity of silver chloride depends on the particle size, but are usually below 100nm. In general, silver chloride is antimicrobial against variousbacteria, such asE. coli.[21]
Silver chloride nanoparticles for use as a microbial agent can be produced by a metathesis reaction between aqueous silver and chloride ions or can bebiogenically synthesized byfungi andplants.[21][22]
Silver chloride's low solubility makes it a useful addition to pottery glazes for the production of "Inglazelustre".Silver chloride has been used as an antidote formercury poisoning, assisting in the elimination ofmercury.Other uses of AgCl include:[4]
Silver chloride occurs naturally aschlorargyrite in the arid and oxidized zones in silver deposits. If some of the chloride ions are replaced by bromide or iodide ions, the words bromian and iodian are added before the name, respectively.[25] This mineral is a source of silver and is leached by cyanidation, where it will produce the soluble [Ag(CN)2]– complex.[4]: 26
According to theECHA, silver chloride may damage theunborn child, is very toxic to aquatic life with long lasting effects and may becorrosive to metals.[26]
... But the first person to use this property to produce a photographic image was German physicist Johann Heinrich Schulze. In 1727, Schulze made a paste of silver nitrate and chalk, placed the mixture in a glass bottle, and wrapped the bottle in ...
| International | |
|---|---|
| National | |
