Silver cyanide
Silver cyanide is the chemical compound with the formula AgCN. It is a white solid that precipitated upon treatment of solutions containing Ag with cyanide, 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 -[Ag-CN]- chains in which the linear two-coordinate Ag ions are bridged by the cyanide ions, typical of silver(I) and other d ions. This is the same binding mode as seen in the more famous case of Prussian blue. 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 ~2.09 Å and the cyanide groups show head-to-tail disorder. Reactions. AgCN precipitates upon the addition of sodium cyanide to a solution containing Ag. The precipitate dissolves upon the addition of further amounts of cyanide to form linear [Ag(CN)] and [Ag(CN)] on the addition of further cyanide. Silver cyanide is also soluble in solutions containing other ligands such as  ammonia or tertiary phosphines. Silver cyanides form structurally complex materials upon reaction with other anions. Some silver cyanides are luminescent. Uses. Both AgCN and KAg(CN) 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 KAg(CN) , 12-120 g·L KCN and 15 g·L KCO.