ammonium chloride, chemical compound, NH₄Cl, a white or colorless, odorless, water-soluble, cubic crystalline salt with a biting taste, commonly known as sal ammoniac. It is prepared commercially by reacting ammonia, NH₃, with hydrogen chloride, HCl, and is used chiefly in the manufacture of electric dry-cell batteries, in soldering fluxes, in textile printing, and in making other compounds. It is also used in certain medical treatments. It occurs in nature in volcanic regions.