Silver chloride
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IUPAC name
Silver(I) chloride
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Other names | |
Identifiers | |
3D model (
JSmol ) |
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ChEBI | |
ChemSpider | |
ECHA InfoCard
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100.029.121 |
PubChem CID
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RTECS number
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UNII | |
CompTox Dashboard (EPA)
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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)
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1.77×10−10[1] |
Solubility | soluble in NH3, conc. HCl, conc. H2SO4, alkali cyanide, (NH4)2CO3, KBr, Na2S2O3; |
−49.0·10−6 cm3/mol | |
Refractive index (nD)
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2.071 |
Structure[2] | |
cubic | |
Fm3m (No. 225) | |
a = 555
pm | |
Octahedral | |
Thermochemistry | |
Std molar
entropy (S⦵298) |
96 J·mol−1·K−1[3] |
Std enthalpy of (ΔfH⦵298)formation |
−127 kJ·mol−1[3] |
Hazards | |
NFPA 704 (fire diamond) | |
Safety data sheet (SDS) | Fischer Scientific, Salt Lake Metals |
Related compounds | |
Other anions
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silver(I) fluoride, silver bromide, silver iodide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Silver chloride is an
It is produced by a metathesis reaction for use in photography and in pH meters as electrodes.
Preparation
Silver chloride is unusual in that, unlike most chloride salts, it has very low solubility. It is easily synthesized by metathesis: combining an aqueous solution of silver nitrate (which is soluble) with a soluble chloride salt, such as sodium chloride (which is used industrially as a method of producing AgCl), or cobalt(II) chloride. The silver chloride that forms will precipitate immediately.[3][4]: 46
It can also be produced by the reaction of silver metal and aqua regia; however, the insolubility of silver chloride decelerates the reaction. Silver chloride is also a by-product of the Miller process, where silver metal is reacted with chlorine gas at elevated temperatures.[4]: 21 [5]
History
Silver chloride has been known since ancient times.
Silver-based photographic films were first made in 1727 by Johann Heinrich Schulze with silver 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 by Nicéphore Niépce.[4]: 38–39 [9]
Structure
The solid adopts the
Above 7.5
Reactions
AgCl dissolves in solutions containing ligands such as chloride, cyanide, triphenylphosphine, thiosulfate, thiocyanate and ammonia. 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 soluble dicyanoargentate 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 produce
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 the qualitative analysis of AgCl in labs as AgCl is white, which changes to (silver arsenite) which is yellow, or (silver arsenate) which is reddish brown.[13]
Chemistry
In one of the most famous reactions in chemistry, the addition of colorless aqueous silver 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 of chloride in solution. Due to its conspicuousness, it is easily used in titration, which gives the typical case of argentometry.[12]
The
For AgBr and AgI, the Ksp values are 5.2 x 10−13 and 8.3 x 10−17, respectively. Silver bromide (slightly yellowish white) and silver iodide (bright yellow) are also significantly more photosensitive than is AgCl.[1][4]: 46
AgCl quickly darkens on exposure to light by disintegrating into elemental chlorine and metallic silver. This reaction is used in photography and film and is the following:[5]
- Cl− + hν → Cl + e− (excitation of the chloride ion, which gives up its extra electron into the conduction band)
- Ag+ + e− → Ag (liberation of a silver ion, which gains an electron to become a silver atom)
The process is not reversible because the silver atom liberated is typically found at a
Uses
Silver chloride electrode
Silver chloride is a constituent of the
Photography
Silver chloride and silver nitrate have been used in photography since it began, and are well known for their light sensitivity.[6] It was also a vital part of the Daguerreotype 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 the gelatin silver process where embedded silver chloride crystals in gelatin were used to produce images.[17] However, with advances in color 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 making photographic paper, since it reacts with photons to form latent images via photoreduction; and in photochromic 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 in sunglasses.[4]
Antimicrobial agent
Silver chloride nanoparticles are widely sold commercially as an
Silver chloride nanoparticles for use as a microbial agent can be produced by a metathesis reaction between aqueous silver and chloride ions or can be
Other uses
Silver chloride's low solubility makes it a useful addition to pottery glazes for the production of "Inglaze lustre". Silver chloride has been used as an antidote for mercury poisoning, assisting in the elimination of mercury. Other uses of AgCl include:[4]
- in bandages and wound healing products,[4]: 83
- to create yellow, amber, and brown shades in stained glass manufacture,[23] and
- as an infrared transmissive optical component, as it can be hot-pressed into window and lens shapes.[24]
Natural occurrence
Silver chloride occurs naturally as chlorargyrite 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
Safety
According to the ECHA, silver chloride may damage the unborn child, is very toxic to aquatic life with long lasting effects and may be corrosive to metals.[26]
See also
References
- ^ ISBN 978-1138561632.
- ^ S2CID 123044752.
- ^ ISBN 978-0-618-94690-7.
- ^ ISBN 9783527303854.
- ^ ISBN 9780750633659.
- ^ ISBN 0-405-04929-3
- ISBN 978-0-7614-1464-3. Retrieved 28 July 2013.
... 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 ...
- ^ Niépce House Museum: Invention of Photography: 1816-1818, Niépce's first tries (retrieved 2024-02-23)
- ISBN 0-19-855370-6. p. 349
- S2CID 45866801.
- ^ ISBN 9780471484943.
- ^ ISBN 0-7514-0389-X.
- ^ "TEST METHOD FOR TOTAL CHLORINE IN NEW AND USED PETROLEUM PRODUCTS BY OXIDATIVE COMBUSTION AND MICROCOULOMETRY" (PDF). Environmental Protection Agency. September 1994. Archived from the original (PDF) on December 3, 2007.
- ^ Bates, R.G. and MacAskill, J.B. (1978). "Standard potential of the silver-silver chloride electrode". Pure & Applied Chemistry, Vol. 50, pp. 1701–1706, http://www.iupac.org/publications/pac/1978/pdf/5011x1701.pdf
- ^ "The Daguerreotype Process". Sussex PhotoHistory. Retrieved 19 June 2023.
- ^ "SILVER GELATIN" (PDF). Getty.edu. Getty. Retrieved 19 June 2023.
- ISBN 9789401042659.
- ISBN 9780122274107. Retrieved 20 June 2023.
- ^ "CVS Health Anti-Microbial Silver Wound Gel". CVS. Retrieved 25 February 2024.
- ^ S2CID 253765691.
- PMID 28773340.
- .
- ^ "Silver Chloride (AgCl) Optical Material". www.crystran.co.uk. Archived from the original on September 5, 2012. Retrieved 2019-12-04.
- ^ "Chlorargyrite". mindat.org. Retrieved 7 June 2023.
- ^ "Brief Profile - ECHA". echa.europa.eu. Retrieved 2024-03-27.