Nickel Diphosphide, NiP₂

Nickel Diphosphide, NiP₂, is prepared by heating an alloy of nickel and tin, containing 5 per cent, of the former metal, with phosphorus in a sealed tube to a temperature of 700° C. If the alloy is heated with less than 20 per cent, of its weight of phosphorus the nickel diphosphide may be isolated from the residue by treatment with warm concentrated hydrochloric acid, in which it is insoluble.

The phosphide is a crystalline substance, of metallic appearance, and of density 4.62 at 18° C.