Chromate of Iron.

Practical Magazine 13, 1876

(Chemistry applied to the Arts, Manufactures, &c. Dyeing, Calico Printing, Bleaching, Tanning, and Allied Subjects.)

If to a solution of neutral chromate of lead be added a solution of chloride of iron sharpened with hydrochloric acid, a dusty precipitate is formed of a bright orange colour. This is chromate of iron, which, dried at 104° Fah., is found to be composed of 65 to 65.11 per cent. of chromic acid and 34.58 to 34.71 of oxide of iron, a composition represented by the formula (Cn. O⁴)³ Fe², and corresponding mathematically to 65.33 of chromic acid with 34.66 of oxide of iron.

This chromate of iron is insoluble in water, easily soluble in hydrochloric, nitric, and sulphuric acids, and decomposes when it is digested in a ley of soda. When strongly heated, it swells and changes to a blackish brown.

Chromate of iron may be conveniently used for oil-painting, for, though in vivacity of colour, it is not equal, to chromate of lead, it has the advantage over it of not blackening under the action of hydro-sulphuric acid, and being in all circumstances without injurious effect on the health. Lastly, chromate of iron may be obtained at a much lower price than chromate of lead.

- Technologiste