3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||133.8856 g/mol|
|Appearance||colorless, gray (impure) crystals|
|Melting point||335 °C (635 °F; 608 K) (decomposes)|
|0.000023 g/100 mL (20 °C)|
|Solubility||soluble in concentrated ammonia, boiling nitric acid, ammonium hydroxide, KCN |
insoluble in alcohol, dilute acid
Refractive index (nD)
Std enthalpy of
|Flash point||320 °C (608 °F; 593 K)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|123 mg/kg (oral, rat)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Silver cyanide is the chemical compound with the formula AgCN. This white solid forms upon treatment of solutions containing Ag+ with cyanide. This precipitation step is used in some schemes to recover silver from solution. Silver cyanide is used in silver-plating.
Its structure consist of -[Ag-CN]- chains in which the linear two-coordinate Ag+ ions, typical of silver(I) and other d10 ions are bridge by the cyanide 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 ofset 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.
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)2]-(aq) and [Ag(CN)3]2-(aq) on the addition of further cyanide. Silver cyanide is also soluble in solutions containing other ligands such as ammonia or tertiary phosphines.
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 KAg(CN)2 15-40 gL-1, KCN 12-120 gL-1 and K2CO3 gL-1.