Chromium Arsenides

Two arsenides, of composition CrAs and Cr₂As₃, respectively, have been obtained. The monarsenide is formed when the sesquiarsenide is heated in hydrogen at 480° to 500° C. Its density at 16° C. is 6.35, and X-ray examination shows that it is hexagonal in structure. It is insoluble in acids. The sesquiarsenide is prepared by heating finely divided chromium with excess of arsenic at 700° C. in a sealed exhausted tube, the product being powdered and again heated. The resulting compound is not changed in composition by prolonged heating in hydrogen at 400° C., but above that temperature it loses arsenic and passes to the monarsenide. Chromium sesquiarsenide is a grey powder, of density 6.2 at 22° C.; it is insoluble in acids.