Prep. In the same manner as the arseniate of iron, phosphate of soda being made use of in the place of arseniate of soda. (Sulphate of iron, three parts; phosphate of soda, two parts and a-half; acetate of soda, one part.) [Sulphate of iron, five parts; phosphate of soda, six parts. U. S.]

Prop. & Comp. The composition of the fresh salt is represented by the formula, 3 Fe O, Po5, but it becomes partially perox-idated by keeping. It is a slate-blue amorphous powder, insoluble in water. Soluble in hydrochloric acid; the solution precipitates both with ferrocyanide and ferrideyanide of potassium, more abundantly with the latter (showing that both proto- and per-salt are present); when treated with tartaric acid and an excess of ammonia, and subsequently with the solution of ammonio-sulphate of magnesia, it lets fall a crystalline precipitate (indicating phosphoric acid). If digested in hydrochloric acid with a lamina of pure copper, a dark deposit does not form on the metal (absence of arsenic).

Off. Prep. Syrupus Ferri Phosphatis. Syrup of Phosphate of Iron. [Not officinal in U. S. P]. (Phosphate of Iron is prepared by precipitating a solution of two hundred and twenty-four grains of granulated sulphate of iron with a mixture of two hundred grains of phosphate, and seventy-four grains of acetate of soda, the precipitate is pressed strongly between folds of bibulous paper, and five fluid ounces and a-half of dilute phosphoric acid added; as soon as the precipitate is dissolved the solution is filtered; and the sugar added and dissolved without heat.)

One grain of the iron salt is contained in each fluid drachm of the syrup.

Therapeutics. The blue phosphate of iron was much used by the late Dr. Prout in the treatment of diabetes. It acts as a blood-restorer like the other preparations of iron, and has been recommended also in the treatment of rickets. The syrup is an agreeable form for its administration.

Dose. 5 gr. to 10 gr. Of the syrup, 1 fl. drm., and upwards.