Ammonium Salt

Ammonium salt A product of a reaction between ammonia, NH₃, and various acids. The general reaction for formation is NH₃ + HX –+ NH₂X. Examples of ammo­nium salts are ammonium chloride, NH₄Cl, ammonium nitrate, NH₄NO₃,  These compounds are ad­dition products of ammonia and the acid. For this reason, their formulas are sometimes written as [H(NH₃)]X.

All ammonium salts decompose into ammonia and the acid when heated. Their stability, however, varies according to the nature of the acid. Salts of weak acids de­compose at lower temperatures than do salts of strong acids.

Ammonium chloride is made by absorbing ammonia in hydrochloric acid. This salt, sometimes called sal ammoniac, is used in galvanizing iron, in textile dyeing, and in manufacturing dry cell batteries.

Ammonium nitrate is prepared from ammonia and nitric acid. It is used as a source of nitrous oxide, N₂0, or laughing gas, and in the manufacture of explosives. A mixture of ammonium nitrate and trinitrotoluene is known as amatol.

Ammonium sulfate, obtained from ammonia and sulfuric acid, is prepared com­mercially by passing ammonia and carbon dioxide, CO₂, into a suspension of finely ground calcium sulfate, CaSO₄. Large quantities are also produced as a byproduct of coke ovens and coal-gas works. The chief use of ammonium sulfate is as a fertilizer.

Ammonium carbonate may be prepared by bringing ammonia and carbon dioxide together in aqueous solution. It is also obtained by heating a mixture of ammonium sulfate and a fine suspension of calcium carbonate.