NH4Cl – ammonium chloride – is a white, odorless, water-soluble, cubic, crystalline compound. The natural, mineralogical form of ammonium chloride is known as sal ammoniac. It occurs in nature as plaque or crusts in volcanic regions and near cracks in the earth's crust. This compound was one of the first chemicals mentioned by ancient scholars and the first compound of ammonia to be discovered. It was a crucial raw material in early industrial activities, primarily employed in dyeing and metallurgical operations. Ammonium chloride was later used as an electrolyte in the Leclanche cell, a type of primary cell. It is also used in medicine to treat some ailments, acting for instance as an expectorant. Nowadays it is used in the production of fertilizers, in the manufacture of certain types of polymers, and as a food additive to licorice-type candy due to its characteristic salty taste.