Silver cyanide is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

AgCN. It is a white salt that is precipitated upon treatment of solutions containing Ag⁺ with

cyanide In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom. Ionic cyanides contain the cyanide anion . This a ...

, which is used in some schemes to recover silver from solution. Silver cyanide is used in silver-plating.

Structure

The structure of silver cyanide consists of - g-CN chains in which the linear two-coordinate Ag⁺ ions are bridged by the cyanide ions, typical of silver(I) and other d¹⁰ ions. This is the same binding mode as seen in the more famous case of

Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...

. These chains then pack hexagonally with adjacent chains offset by +/- 1/3 of the ''c'' lattice parameter. This is the same as the structure adopted by the high temperature polymorph of copper(I) cyanide. The silver to carbon and silver to nitrogen bond lengths in AgCN are both ~2.06 Å and the cyanide groups show head-to-tail disorder.

Reactions

AgCN precipitates upon the addition of

sodium cyanide Sodium cyanide is a compound with the formula Na C N and the structure . It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also expl ...

to a solution containing Ag⁺. On the addition of further cyanide, the precipitate dissolves to form linear g(CN)₂sup>−_(aq) and g(CN)₃sup>2−_(aq). Silver cyanide is also soluble in solutions containing other ligands such as ammonia or tertiary

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

s. Silver cyanides form structurally complex materials upon reaction with other anions. Some silver cyanides are luminescent.

Uses

"Cyanidation" is widely used in the isolation of silver from its ores. Partial purification of silver compounds is usually effected by froth flotation. The silver ion is then separated from the skimmed froth with cyanide, yielding a solution of g(CN)₂sup>−. The silver metal can then be plated out by electrolysis of such solutions. Both AgCN and KAg(CN)₂ have been used in silver-plating solutions since at least 1840 when the Elkington brothers patented their recipe for a silver-plating solution. A typical, traditional silver-plating solution would contain 15-40 g·L⁻¹ KAg(CN)₂ , 12-120 g·L⁻¹ KCN and 15 g·L⁻¹ K₂CO₃.

References

{{Silver compounds Cyanides Silver compounds

Structure

Reactions

Uses

See also

References