This somewhat rare metal occurs chiefly in native lead chromate or crocoisite (PbCrO4), and in chrome-iron ore or chromite (FeO.Cr203), the. latter of which is mainly used for the preparation of chromium compounds. The metal is isolated by reducing the oxide or chloride. Deville intensely heats a mixture of sugar and chromic oxide in a lime crucible. Wtth-ler heats chromium sesquichloride with metallic zinc under a layer of sodium chloride, and treats the zinc regulus with nitric acid, when the chromium separates as a grey metallic powder. Bunsen obtains the metal in brittle glistening scales by electrolysis of a solution of chromous chloride containing chromic chloride. Fremy procures it in hard crystalline scales by heating chromic chloride in contact with sodium vapour in an atmosphere of hydrogen. Vincent finds that when chromium amalgam is heated in an atmosphere of petroleum, the metal remains behind in a pulverulent form. Finally, Zettnow has shown that when the metallic regulus formed by fusing the double chloride of chromium and potassium'with zinc is treated with nitric acid, a residue of crystalline chromium is left.
The sp. gr. of the metal forming a greenish crystalline powder is variously stated at 6.81 to 7.3. The metal is undissolved by hot concentrated nitric acid; slowly by cold dilute sulphuric, but rapidly on warming; and quickly in hydrochloric. Devilled fused metal is non-magnetic, as hard as corundum, and less easily melted than platinum; it oxidizes slowly when heated in the air or hydrogen, and burns brightly in the oxy-hy-drogen flame. (See Alloys, p. 23.)