Ammonium bromide

 ( Ammonium Compounds ) 

Ammonium bromide, NH₄Br, is the ammonium salt of hydrobromic acid. The chemical crystallizes in colorless prisms, possessing a Salt 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⁻) to bromine (Br₂).

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Preparation Ammonium bromide can be prepared by the direct action of hydrogen bromide on ammonia.

NH₃ + HBr → NH₄Br

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.

2 NH₃ + FeBr₂ + 2 H₂O → 2 NH₄Br + Fe(OH)₂

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Reactions Ammonium bromide is a weak acid with a p K_a of approximately 9 in water. It is an acid salt because the ammonium ion hydrolysis slightly in water.

Ammonium bromide is a strong electrolyte when put in water:

NH₄Br(s) → (aq) + Br⁻(aq)

Ammonium bromide decomposes to ammonia and hydrogen bromide when heated at elevated temperatures:

NH₄Br → NH₃ + HBr

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Uses Ammonium bromide is used for photography in , plates and ; in fireproofing of wood; in lithography and process engraving; in corrosion inhibitors; and in pharmaceutical preparations.Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002,

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