Copper polysulphides

An orange-red substance of the formula CuS₃ is obtained by fusing cupric sulphate with sodium carbonate and sulphur. Heating with carbon disulphide converts it into an amorphous, dark-brown substance, Cu₂S₃. Another polysulphide, Cu₂S₅, is stated to be formed by the interaction at 0° C. of a solution of cupric acetate and calcium polysulphide. It has a reddish-brown colour. It is doubtful whether any of these polysulphides is a true chemical compound.