Calcium Platinocyanide, CaPt(CN)₄

Calcium Platinocyanide, CaPt(CN)₄.5H₂O, may be prepared in a similar manner to the barium salt. It crystallises in rhombic prisms, having the following crystallographic elements:

a:b: с = 0.89956: 1: 0.34943

Levy has shown that two isomeric varieties of the pentahydrate exist, analogous to the two isomerides of the tetrahydrate of barium platinocyanide. The a-salt may be described as golden yellow with green fluorescence on the pyramid faces, whilst the β-salt shows a green fluorescence on all faces, which is particularly intense on the tops of the crystals. The crystalline characters of the two isomerides are identical.

The α-salt is obtained by crystallisation from a solution containing a small quantity of acid, and the β-salt from one containing some hydroxyl or cyanide ions, precisely as in the case of the α and β barium platinocyanides.

Anhydrous calcium platinocyanide, CaPt(CN)₄, is white, and exhibits only a feeble fluorescence.