Ammonium chloride (NH4Cl) is a salt formulation of ammonia and hydrogen chloride. It is a colorless crystalline substance, and soluble in water forming an acidic solution. Commercially, ammonium chloride is used as a nitrogen source for fertilizer. It is also used as an electrolyte, and it also is found in many pharmaceuticals preparations such as cough and cold medications, and has been used as an expectorant to help clear lung secretions. 

Production

Ammonium chloride is a product of the Solvay process used to produce sodium carbonate:

CO2 + 2 NH3 + 2 NaCl + H2O → 2 NH4Cl + Na2CO3

In addition to being the principal method for the manufacture of ammonium chloride, that method is used to minimize ammonia release in some industrial operations.

Ammonium chloride is prepared commercially by combining ammonia (NH3) with either hydrogen chloride (gas) or hydrochloric acid (water solution):

NH3 + HCl → NH4Cl

Reactions

Ammonium chloride occurs naturally in volcanic regions, forming on volcanic rocks near fume-releasing vents (fumaroles). The crystals deposit directly from the gaseous state and tend to be short-lived, as they dissolve easily in water.

Ammonium chloride appears to sublime upon heating but actually decomposes into ammonia and hydrogen chloride gas.

NH4Cl → NH3 + HCl

Ammonium chloride reacts with a strong base, like sodium hydroxide, to release ammonia gas:

NH4Cl + NaOH → NH3 + NaCl + H2O

Similarly, ammonium chloride also reacts with alkali metal carbonates at elevated temperatures, giving ammonia and alkali metal chloride:

2 NH4Cl + Na2CO3 → 2 NaCl + CO2 + H2O + 2 NH3

A 5% by weight solution of ammonium chloride in water has a pH in the range 4.6 to 6.0.

Some of ammonium chloride's reactions with other chemicals are endothermic like its reaction with barium hydroxide and its dissolving in water.