Prep. By mixing solutions of phosphoric acid and ammonia, and collecting the crystalline product which results.

Prop. & Comp. Phosphate of ammonia, 3 Nh4 O, Po5 + 5 HO, forms large transparent prisms, which effloresce on exposure to air; it is soluble in water, insoluble in rectified spirit; heated with potash it evolves ammonia; it gives a canary-coloured precipitate with nitrate of silver; and when acidulated with hydrochloric acid is not affected by sulphuretted hydrogen. If 20 grains of this salt be dissolved in water and the solution of ammonio-sulphate of magnesia be added, a crystalline precipitate (ammonia-magnesian phosphate) falls, which when well washed upon a filter with solution of ammonia diluted with an equal volume of water, dried and heated to redness, leaves 11.44 grains.

Therapeutics. Phosphate of ammonia, when in solution, is capable of dissolving a considerable amount of urate of soda; and clinical experience has shown that it is of great value in the treatment of certain urinary diseases, where a tendency to uric acid calculi exists, and also in certain conditions of the gouty habit.

Dose. 5 gr. to 20 gr. freely diluted.

The Iodide and the Bromide of ammonium have been sometimes used in medicine.

The Iodide of Ammonium seems to have nearly the same action as the iodide of potassium; it forms a white crystalline salt, and may be given in the same doses as the last-named salt. See Potassii Iodidum.

The Bromide of Ammonium has been used in some cases as an anaesthetic to deaden the sensibility of the fauces and palate, and in some forms of convulsive diseases, as pertussis, etc. The action is probably the same as that of the bromide of potassium. The dose is five to ten or even fifteen grains. See Potassii Bromidum.