Ammonium bromide, NH<sub>4</sub>Br, is the ammonium salt of hydrobromic acid. The chemical crystallizes in colorless prisms, possessing a saline taste; it sublimes on heating and is easily soluble in water. On exposure to air it gradually assumes a yellow color because of the oxidation of bromide (Br<sup>âÂÂ</sup>) to bromine (Br<sub>2</sub>).
Ammonium bromide can be prepared by the direct action of hydrogen bromide on ammonia.
It can also be prepared by the reaction of ammonia with iron(II) bromide or iron(III) bromide, which may be obtained by passing aqueous bromine solution over iron filings.
Ammonium bromide is a weak acid with a pK<sub>a</sub> of approximately 9 in water. It is an acid salt because the ammonium ion hydrolyzes slightly in water.
Ammonium bromide is a strong electrolyte when put in water:
Ammonium bromide decomposes to ammonia and hydrogen bromide when heated at elevated temperatures:
Ammonium bromide is used for photography in films, plates and papers; in fireproofing of wood; in lithography and process engraving; in corrosion inhibitors; and in pharmaceutical preparations.