Chromium Oxide Powder - Cr2O3

Chromium(III) oxide is the inorganic compound of the formula Cr2O3. It is one of principal oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite.

Cr2O3 adopts the corundum structure, consisting of a hexagonal close packed array of oxide anions with 2/3 of the octahedral holes occupied by chromium. Similar to corundum, Cr2O3 is a hard, brittle material (Mohs hardness 8-8.5). It is antiferromagnetic up to 307 K, the Neel temperature.It is not readily attacked by acids or bases, although molten alkali gives chromates (salts with the CrO2−4 anion, not to be confused with the related mineral chromite). It turns brown when heated, but reverts to its dark green color when cooled. It is also hygroscopic.

Because of its considerable stability, chromia is a commonly used pigment and was originally called viridian. It is used in paints, inks, and glasses. It is the colourant in "chrome green" and "institutional green." Chromium(III) oxide is a precursor to the magnetic pigment chromium dioxide, according to the following reaction: 

Cr2O3 + 3 CrO3 → 5 CrO2 + O2

It is one of the materials that are used when polishing (also called stropping) the edges of knives, razors, etc. on a piece of leather, balsa, cloth, or other material. In this context it is alternatively known as "green compound".