Tri-cobalt Di-arsenide, Co₃As₂

Tri-cobalt Di-arsenide, Co₃As₂, may be prepared by the action of arsenic chloride on metallic cobalt at 800-1400° C.; or by heating mixtures of arsenic and cobalt in hydrogen or carbon monoxide at this temperature. It is also formed when powdered cobalt is heated in hydrogen containing arsenic vapour, and when cobalt arsenate or arsenite is reduced by hydrogen at 900° C. Its density is 7.82, and it loses arsenic when strongly heated.