Chromium Nitrides

The absorption of nitrogen by finely divided chromium begins at 800° to 820° C.; the metal does not melt; the product, which is distinctly magnetic, contains 8 per cent, of nitrogen. On heating to 850° C. in ammonia, chromium yields a dull black nitride, Cr₃N₂, containing small quantities of unchanged chromium.

A nitride of chromium, CrN, is formed when the violet sesquioxide is heated in a current of dry ammonia, when chromic and ammonium chlorides are heated together in hydrogen, or when chromium amalgam is distilled in nitrogen. On heating the nitride in hydrogen no reduction is observed; the brown insoluble powder, on heating in air, burns to nitrogen and chromic oxide, and on heating in ammonia is said to yield the nitride Cr₃N.