When heated, ammonium chloride decomposes into ammonia and hydrogen chloride. The visible effect of this reaction is that the compound appears to sublimate into a gaseous state. When the gases cool, they crystallize into their original state: solid ammonium chloride.
Ammonium chloride is called sal ammoniac when found in nature. It forms near burning coal dumps and on volcanic rocks when gaseous ammonia and hydrogen chloride cool and crystallize. Laboratory-produced ammonium chloride does not use this process; instead, ammonia and hydrogen chloride or hydrochloric acid are combined directly.
Ammonium chloride is soluble in water and is slightly acidic in solution. In addition to its water solubility, it is soluble in ammonia, acetone, alcohol and hydrazine. It is an odorless solid that does not melt.
Its primary commercial use is in fertilizer, particularly as a rice fertilizer in Japan. It is also used in metalwork as a soldering flux, in cough medicines as an expectorant, in fireworks to enhance blue and green colors, and as a food additive. When used as a food additive, ammonium chloride is labeled as 'sal ammoniac' or additive E510. It is approved as a baking additive and a liquorice flavoring. E510 is used as an acidity regulator, flavour enhancer and as a nutrient for yeast in yeast-fermented products such as bread.