What happens if you heat ammonium chloride

Ammonium chloride

Author: Hans Lohninger

CAS no.12125-02-9
molar mass53.49
Melting point
[1 bar]
[34.5 bar]

338 ° C (decomposition)
520 ° C
boiling point-
density1.53 g / cm3
solubility in water
[20 ° C]
[100 ° C]

372 g / L
773 g / L

Ammonium chloride ("salmiac"(1)), NH4Cl, is a colorless substance that is very soluble in water. Ammonium chloride is highly corrosive because it reacts acidic in aqueous solution, can complex metal ions and release chloride ions, which especially damage many types of steel.

When heated, ammonium chloride breaks down into ammonia and hydrogen chloride. Since the two gaseous decomposition products react with each other again immediately on cooling and form ammonium chloride, one gets the impression that ammonium chloride sublimes (which is wrong, however).

In the laboratory, ammonium chloride can be prepared by mixing 20% ​​ammonia solution with concentrated hydrochloric acid and then evaporating the solution:

NH3 + HCl NH4Cl

Large-scale production takes place either by reacting ammonia water with hydrochloric acid, or by adapting the Solvay process. With the modified Solvay process, the ammonia is no longer recovered, so that when ammonia is consumed, approximately equal proportions by weight of soda and ammonium chloride are produced and no calcium chloride is produced as waste:

2 NaCl + 2 NH3 + CO2 + H2O N / A2CO3 + 2 NH4Cl

After drying, the ammonium chloride produced contains less than 0.1% by weight of water, but nevertheless tends to cake. In order to prevent caking - depending on the application - approx. 0.5% boron trioxide, B2O3 added; Ammonium chloride for use in food may not contain any anti-caking agents in Europe.

In terms of quantity, the most important application of ammonium chloride is its use in nitrogen fertilizers for rice plantations in China and Japan. It is also used in large quantities as an electrolyte in dry batteries. Ammonium chloride is also used as an additive in fireproof explosives for underground coal mining. It is also suitable as a flux additive for tinning, galvanizing and soldering.