 40 grams of silver cyanide on ascale. | |
| Names | |
|---|---|
| IUPAC name Silver cyanide | |
| Other names Argentous cyanide | |
| Identifiers | |
| |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.007.317 |
| EC Number |
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| RTECS number |
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| UNII | |
| UN number | 1684 |
| |
| |
| Properties | |
| AgCN | |
| Molar mass | 133.8856 g/mol |
| Appearance | colorless, gray (impure) crystals |
| Odor | odorless |
| Density | 3.943 g/cm3 |
| Melting point | 335 °C (635 °F; 608 K) (decomposes) |
| 0.000023 g/100 mL (20 °C) | |
Solubility product (Ksp) | 5.97×10−17[1] |
| Solubility | soluble in concentratedammonia, boilingnitric acid,ammonium hydroxide,KCN insoluble inalcohol, diluteacid |
| −43.2·10−6 cm3/mol | |
Refractive index (nD) | 1.685 |
| Structure | |
| hexagonal | |
| linear | |
| Thermochemistry | |
Std molar entropy(S⦵298) | 84 J·mol−1·K−1[2] |
Std enthalpy of formation(ΔfH⦵298) | 146 kJ·mol−1[2] |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | toxic |
| GHS labelling: | |
   | |
| Danger | |
| H290,H300,H310,H315,H318,H330,H410 | |
| P234,P260,P262,P264,P270,P271,P273,P280,P284,P301+P310,P302+P350,P302+P352,P304+P340,P305+P351+P338,P310,P320,P321,P322,P330,P332+P313,P361,P362,P363,P390,P391,P403+P233,P404,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | 320 °C (608 °F; 593 K) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 123 mg/kg (oral, rat) |
| Related compounds | |
Otheranions | AgCl |
Othercations | NaCN Copper(I) cyanide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Silver cyanide is thechemical compound with theformula AgCN. It is a white salt that isprecipitated upon treatment of solutions containing Ag+ withcyanide, which is used in some schemes to recover silver from solution. Silver cyanide is used in silver-plating.
The structure of silver cyanide consists of -[Ag-CN]- chains in which the linear two-coordinate Ag+ ions are bridged by the cyanide ions,[3] typical of silver(I) and other d10 ions. This is the same binding mode as seen in the more famous case ofPrussian blue. These chains then pack hexagonally with adjacent chains offset by +/- 1/3 of thec lattice parameter. This is the same as the structure adopted by the high temperature polymorph ofcopper(I) cyanide. The silver to carbon and silver to nitrogen bond lengths in AgCN are both ~2.06 Å[4] and the cyanide groups show head-to-tail disorder.[5]
AgCN precipitates upon the addition ofsodium cyanide to a solution containing Ag+. On the addition of further cyanide, the precipitate dissolves to form linear [Ag(CN)2]−(aq) and [Ag(CN)3]2−(aq). Silver cyanide is also soluble in solutions containing other ligands such as ammonia or tertiaryphosphines.
Silver cyanides form structurally complex materials upon reaction with other anions.[6] Some silver cyanides areluminescent.[7]
"Cyanidation" is widely used in the isolation of silver from its ores. Partial purification of silver compounds is usually effected byfroth flotation. The silver ion is then separated from the skimmed froth with cyanide, yielding a solution of [Ag(CN)2]−. The silver metal can then be plated out by electrolysis of such solutions.[8]
Both AgCN andKAg(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.[9]
