Platinous Cyanide, Pt(CN)₂

Platinum Dicyanide, Platinous Cyanide, Pt(CN)₂, appears to have been first obtained by Doebereiner as the result of heating mercuric platinocyanide, HgPt(CN)₄. It also results on treating the double potassium salt, K₂Pt(CN)₄ with chlorine, and by heating the ammonium salt, (NH₄)₂Pt(CN)₄, to 200° C. or 300° C. When mercuric cyanide is added to a solution of an alkali chlor-platinite, the liquid is decolorised, and platinous cyanide is deposited as a pale yellow precipitate.4 Prepared in these ways, platinous cyanide possesses a yellow colour. It is insoluble in alkalies and potassium cyanide, for which reason it cannot be used in preparing platinocyanides. When heated it burns, yielding metallic platinum.

A soluble form of platinous cyanide is obtained as a yellow precipitate by decomposing a solution of a platinocyanide with sulphuric acid. It dissolves easily in alkalies and in potassium cyanide solution, but is usually contaminated with small quantities of sulphate.