silver chloride

Silver chloride
IUPAC name	Silver(I) chloride
Other names	cerargyrite, chlorargyrite, horn silver
Identifiers
CAS number	[7783-90-6]
RTECS number	VW3563000
Properties
Molecular formula	AgCl
Molar mass	143.32 g mol−1
Appearance	White Solid
Density	5.56 g.cm3
Melting point	457 °C
Boiling point	1547 °C
Solubility in water	520 μg/100 g at 50 °C
Solubility in water	insoluble in alcohol, dilute acid soluble in ammonia, concentrated sulfuric acid, alkali cyanide, NH4CO3, KBr, sodium thiosulfate
Refractive index (nD)	2.071
Structure
Crystal structure	halite
Thermochemistry
Std enthalpy of formation ΔfHo298	−127.01 kJ mol−1
Standard molar entropy So298	96.25 J mol−1 K−1
Hazards
MSDS	Salt Lake Metals
NFPA 704	0 2 0
Related compounds
Other anions	silver(I) fluoride, silver bromide, silver iodide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Silver chloride is a chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water (this behavior being reminiscent of the chlorides of Tl⁺ and Pb²⁺). Upon illumination or heating, silver chloride converts to silver (and chlorine), which is signalled by greyish or purplish coloration to some samples. AgCl occurs naturally as a mineral chlorargyrite.

Structure and reactions

The solid adopts the fcc NaCl structure, in which each Ag⁺ ion is surrounded by an octahedron of six chloride ligands. AgF and AgBr crystallize similarly.^[1] However, the crystallography depends on the condition of crystallization, primarily free silver ion concentration. 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:

AgCl(s) + Cl⁻(aq) → AgCl₂⁻(aq)

AgCl(s) + 2S₂O₃²⁻(aq) → Ag[(S₂O₃)₂]³⁻(aq) + Cl⁻(aq)

AgCl(s) + 2NH₃(aq) → Ag[(NH₃)₂]⁺(aq) + Cl⁻(aq)

Most complexes derived from AgCl are two-, three-, and, in rare cases, four-coordinate, adopting linear, trigonal planar, and tetrahedral coordination geometries, respectively.

Chemistry

In one of the most famous reactions in chemistry, addition of colorless aqueous silver nitrate to an equally colorless solution of sodium chloride produces an opaque white precipitate of AgCl which quicky darkens on exposure to light:^[2]

Ag⁺(aq) + Cl⁻(aq) → AgCl(s)

This conversion is a common test for the presence of chloride in solution. The solubility product, K_sp, for AgCl is 1.8 x 10⁻¹⁰, which indicates that one liter of water will dissolve 0.000013 moles (1.9 mg) of AgCl at room temperature. 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 is unreactive toward water. Ions that interfere with this test are bromide and iodide, as well as a variety of ligands (see silver halide). For AgBr and AgI, the K_sp values are 5.2 x 10⁻¹³ and 8.3 x 10⁻¹⁷, respectively. The silver bromide (slightly yellowish white) and silver iodide (pale yellow) are also significantly more photosensitive than is AgCl.

Uses

• Silver chloride is used to make photographic paper since it reacts with photons to form latent image and via photoreduction.
• The Silver Electrode is a common reference electrode in electrochemistry.
• 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.
• Silver chloride is often used in photochromic lenses, again taking advantage of its reversible conversion to Ag metal.
• Silver chloride is used to create yellow, amber, and brown shades in stained glass manufacture.
• Silver chloride is used in bandages and wound healing products.

Footnotes

1. ^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
2. ^ More info on Chlorine test: [1]

External links

• Silver Chloride Data Sheet
• Science Lab.com MSDS for silver chloride
• Salt Lake Metals.com MSDS for Silver Chloride
• Solubility of Silver Chloride in various solutions - plus Lab Notes