Calcium Perthiocarbonate

If a stream of hydrogen saturated with carbon disulphide vapour be passed through an aqueous solution of calcium polysulphide, and the solution evaporated in vacuo, dark red needles of composition CaCS₄.2Ca(OH)₂.8H₂O are deposited.

When alcoholic solutions are employed, addition of ether precipitates oils which take a long time to crystallise. These contain perthiocarbonate and also a large and varying amount of calcium thiosulphate. On drying in vacuo, or in a current of hydrogen, they decompose, leaving hydrated calcium polysulphides.