Disulphur Dithiocyanate, S₂(SCN)₂

Disulphur Dithiocyanate, S₂(SCN)₂, is formed by the interaction of sulphur chloride and a metallic/thiocyanate, the best and most uniform results being obtained when mercuric thiocyanate is used. Chloroform or carbon tetrachloride forms a suitable solvent if the product is only required in solution, since these do not dissolve mercury salts; if the compound is to be isolated, carbon disulphide is the required solvent. Disulphur dithiocyanate forms colourless crystals which melt at -3.3° C., forming a viscous, yellow, odourless liquid, which is somewhat unstable. On cautious heating it becomes dark yellow, then red, and finally detonates. It is hydrolysed by water according to the equations:

S₂(SCN)₂ + 2H₂O → HO.S.S.OH + 2HCNS,
HO.S.S.OH + 2HCNS → 2S + 2H₂O + (SCN)₂,
and
3(SCN)₂ + 4H₂O → 5HCNS + H₂SO₄ + HCN.