Origin. - It is prepared by dissolving potassium iodide and ammonium sulphate in boiling water, adding alcohol, filtering, washing the filtrate, and evaporating it to dryness.

Description and Properties. - Minute, colorless, cubical crystals, or a white, granular powder, without odor when colorless, but emitting a slight odor when colored, and having a sharp, saline taste. The salt is hygroscopic, and soon becomes yellow, or yellowish-brown, on exposure to the air and light, owing to the loss of ammonia and the elimination of iodine. Soluble in 0.6 part of water and in 9 parts of alcohol. Ammonium iodide should be kept in small, well-stoppered vials, protected from light.

Dose. - 3-20 grains (0.18-1.2 Gm.) [4 grains (0.25 Gm.), U. S. P.].