Cadmium Cyanide, Cd(CN)₂

White crystalline Cadmium Cyanide, Cd(CN)₂ has been precipitated from a saturated solution of cadmium sulphate with concentrated potassium cyanide solution, and in a similar way, as a voluminous, more amorphous mass, the salt has been precipitated from a fairly concentrated solution of cadmium chloride. Rammelsberg evaporated a solution of freshly precipitated cadmium hydroxide in hydrocyanic acid, but, according to Joannis, some insoluble basic cadmium cyanide, 2Cd(CN)₂.CdO.5H₂O, is simultaneously produced.

One hundred c.c. of water at 15° C. dissolve 1.7 grm. Cd(CN)₂. It dissolves in acids and is insoluble in ammonium chloride solution. It is stable in air, but on ignition leaves cadmium oxide, or, if access of air is restricted, metallic cadmium.

The heat of formation of cadmium cyanide is 40.0 Cal. from solid cadmium and gaseous cyanogen, and of 2Cd(CN)₂.CdO.5H₂O, 22.0 Cal.

The diammoniate of cadmium thiocyanate, Cd(CNS)₂.2NH₄, is analogous to the corresponding zinc compound and is similarly prepared.