Uranyl Thiocyanate, UO₂(CNS)₂

Uranyl Thiocyanate, UO₂(CNS)₂.8H₂O, may be obtained by the addition of barium thiocyanate to a solution of uranyl sulphate, and evaporation of the resulting red solution in a vacuum over sulphuric acid. It separates in orange-yellow needles, which are very hygroscopic and readily dissolve in water, alcohol, ether, and acetone; ether may be used for extracting it from its aqueous solution. The addition of pyridine to its aqueous solution precipitates a crystalline basic salt of composition 5UO₂(CNS)₂.UO₃.xH₂O.

Double salts of the types R^•₃UO₂(CNS)₅.6H₂O and R^•₅UO₂(CNS)₇.2H₂O are formed on the addition of an alkali thiocyanate to a solution of uranyl thiocyanate. On evaporation, the double compound separates in orange-yellow to dark red, very deliquescent, crystals. The alkaline earth metals only form double salts of the type R^••UO₂(CNS)₄.6H₂O. None of these double thiocyanates in aqueous solution exhibits the properties of a complex salt. Cryoscopic measurements indicate a complete dissociation into the simple ions.