Short notes on the Chemical composition, Physical properties and Uses of Chromites

Chemical composition: Chromate is composed of iron, chromium oxygen. In the purest form it is FeCr, 04 (Fe =25% Cr = 46% and 29%). Sometimes chromium is replaced by minor amounts of Mg, A1 Zn.

Physical properties:

(i) Form: Massive, granular course to fine grained; crystallized varieties are octahedral.

(ii) Colour: Iron black to brownish black.

(iii) Lustre: Submetallic.

(iv) Streak: Brown.

(v) Hardness: 5-6.

(vi) Cleavage: Absent.

(vii) Fracture: Conchoidal.

(viii) Specific gravity: 4.5 – 4.8. (xii) Diaphaneity: Opaque

(ix) Magnetic property: Moderately magnetic.

Use:

Chromate is used for extraction of chromium metal, preparation of stainless steel, refractory bricks and pigments.