Potassium auricyanide is transformed by strong acids such as hydrofluosilicic acid into auric cyanide. The reaction is more complex than is indicated by the equation
2KAu(CN)4+H2SiF6 = 2Au(CN)3+K2SiF6+2HCN.
Evaporation of the solution over sulphuric acid yields the salt in large colourless leaflets of the formula Au(CN)3,3H2O or 2Au(CN)3,3H2O, which melt at 50° C., and decompose at higher temperatures. On evaporation, its solution in water decomposes. |