Ammonium bromide, NH₄Br, 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 A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retard ...

(Br⁻) to

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

(Br₂).

Preparation

Ammonium bromide can be prepared by the direct action of

hydrogen bromide Hydrogen bromide is the inorganic compound with the formula . It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temper ...

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

. : NH₃ + HBr → NH₄Br It can also be prepared by the reaction of ammonia with

iron(II) bromide Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

iron(III) bromide Iron(III) bromide is the chemical compound with the formula FeBr3. Also known as ferric bromide, this red-brown odorless compound is used as a Lewis acid catalyst in the halogenation of aromatic compounds. It dissolves in water to give acidic s ...

, which may be obtained by passing aqueous bromine solution over iron filings. : 2 NH₃ + FeBr₂ + 2 H₂O → 2 NH₄Br + Fe(OH)₂

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 Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleu ...

ion hydrolyzes slightly in water. Ammonium bromide is a strong electrolyte when put in water: :NH₄Br(s) → (aq) + Br⁻(aq) Ammonium bromide decomposes to ammonia and

when heated at elevated temperatures: : NH₄Br → NH₃ + HBr

Uses

Ammonium bromide is used for photography in

film A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...

s, plates and

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses, Feces#Other uses, herbivore dung, or other vegetable sources in water. Once the water is dra ...

s; in fireproofing of wood; in

lithography Lithography () is a planographic method of printing originally based on the miscibility, immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It was invented in 1796 by ...

and process engraving; in corrosion inhibitors; and in pharmaceutical preparations.Pradyot Patnaik. ''Handbook of Inorganic Chemicals''. McGraw-Hill, 2002,

References

{{bromides Ammonium compounds Bromides Nonmetal halides