Cyanogen Triselenide, Se₃(CN)₂

Cyanogen Triselenide, Se₃(CN)₂, may be prepared by the action of a current of chlorine diluted with air on an aqueous solution of potassium selenocyanate, KCNSe. It may also be advantageously obtained by the action of nitric oxide on a paste of potassium selenocyanate with water.

It crystallises from water in needles which melt at 132° C. and decompose at 148.5° C. From chloroform solution it crystallises in golden-yellow tabular crystals. Some selenium is deposited from its ether and alcohol solutions. It is soluble in benzene and in carbon disulphide.

When acted on by hot water, cyanogen triselenide reacts according to the equation:

2Se₃(CN)₂ + 2H₂O = 5Se + SeO₂ + 4HCN.

Calcium carbonate decomposes the triselenide thus:

2Se₃(CN)₂ + 3CaCO₃ = 2Ca(CNSe)₂ + CaSeO₃ + Se + 3CO₂.

The triselenide acts vigorously on many organic compounds with production of selenium, but the exact course of the reaction has not been ascertained in any one case as the products appear to be of a complex character.