Cobalt Subphosphide, Co₂P

Cobalt Subphosphide, Co₂P may be obtained by heating finely divided cobalt with copper phosphide in the electric furnace; by heating pellets of the metal with red phosphorus in a crucible, covering with barium chloride, and raising to the melting-point; and by exposing reduced cobalt at bright red heat to vaperistd phosphorus trichloride, tribromide, or tri-iodide.

Cobalt subphosphide crystallises in grey needles, melting at 1886° C., of density 6.3 to 6.6, and of hardness 6. At 920° C. it undergoes polymorphic change. It dissolves in concentrated nitric acid, and is slowly attacked by sulphuric and hydrochloric acids.