Synonym. - Ferrum Phosphoricum.

Present name. - Ferrous Hydric Phosphate. Fe"Hpo4.

The Ferri Phosphas of the British Pharmacopoeia consists of Ferrous Hydric Phosphate, mixed with an uncertain amount of Ferric Phosphate, Fe"'Po4 It is prepared as follows: -

Take of

Sulphate of Iron . . . . .

3 ounces;

Phosphate of Soda .

2 1/2 ounces;

Acetate of Soda .....

1 ounce;

Boiling Distilled Water . . . .

4 pints.

Dissolve the Sulphate of Iron in one half of the water, and the Phosphate and Acetate of Soda in the remaining half. Mix the two solutions, and, after careful stirring, transfer the pre-cipitate to a calico filter, and wash it with hot distilled water till the filtrate ceases to give a precipitate with Chloride of Barium. Finally., dry the precipitate at a temperature not exceeding 120°.

Characters and Tests. - A slate-blue amorphous powder, in-soluble in water, soluble in Hydrochloric Acid. The solution yields a precipitate with both the yellow and red Prussiate of Potash, that afforded by the latter being the more abundant; and when treated with Tartaric Acid and an excess of Ammonia, and subsequently with the solution of Ammonio-sulphate of Magnesia, lets fall a crystalline precipitate. When the salt is digested in Hydrochloric Acid with a lamina of pure Copper, a dark deposit docs not form on the metal. 20 grains dissolved in Hydrochloric Acid continue to give a blue precipitate with red Prussiate of Potash until 250 grain measures of the volumetric solution of Bichromate of Potash have been added.

Preparation. - Trituration.