Ammonium chloride is a white solid. It breaks down when heated, forming ammonia and hydrogen chloride. When these two gases are cool enough, they react together to form ammonium chloride again.

Ammonium ions (NH 4 +) – found in ammonium compounds such as ammonium chloride, ammonium nitrate and ammonium sulfate – can be identified by heating a solution of the ions with sodium hydroxide.