Silver chloride

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.

Coordination chemistry
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. AgCl dissolves in solutions containing ligands such as chloride, triphenylphosphine, thiosulfate, and ammonia. Silver chloride reacts with these ligands according to the following illustrative equations:
 * AgCl(s) +  Cl–(concentrated, aqueous)  →  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.

In one of the most famous reactions in chemistry, addition of aqueous silver nitrate to an equally colourless solution of sodium chloride produces an opaque white precipitate of AgCl:
 * Ag+(aq) +  Cl-(aq)  →  AgCl(s)

This conversion is a common test for the presence of chloride in solution. The solubility product, Ksp, for AgCl is 1.8 x 10-10, which indicates that one liter of water will dissolve 0.000013 grams of AgCl. 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 ligand. For AgBr and AgI, the values are 5.2 x 10-13 and 8.3 x 10-17, respectively. The bromide (tan) and iodide (yellow) are also significantly more photosensitive than is AgCl.

Applications

 * Silver chloride is used to make photographic film and photographic paper since it converts to gray-black metallic Ag via photoreduction.
 * The Silver Chloride 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.