Tungsten Diarsenide, WAs₂

Tungsten Diarsenide, WAs₂, is prepared by heating pure tungsten hexachloride in a current of hydrogen arsenide, the temperature being maintained at 150° to 200° C. for a time and then gradually raised to 350° C. The arsenide remains as a black crystalline mass, of density 6.9 at 18° C. It is stable in air at ordinary temperature; at red heat it is readily oxidised, leaving a residue of yellow tungstic anhydride. It readily combines with chlorine, sulphur, and phosphorus when heated. It is quite insoluble in water, carbon disulphide, and the usual organic solvents; solutions of hydrofluoric and hydrochloric acids have no action upon it, but nitric acid and aqua regia oxidise it on warming. Fused alkalies and alkali carbonates act upon it to form arsenate and tungstate.