Ammonium chloride
Ammonium chloride is assigned the chemical formula NH4Cl. It is a colourless, crystalline solid that is the ammonium salt of hydrochloric acid. Ammonium chloride is found in its natural form as a mineral known as salmiak.
Properties of Ammonium Chloride
Ammonium chloride is colourless and forms cubic crystals. It dissolves well in water. The aqueous solution reacts acidically because of the so-called salt hydrolysis of the ammonium cation. The pH value of a 1 percent solution is about 5.5. Ammonium chloride can be purified from water by recrystallisation. The salt dissolves poorly in ethanol, and is hardly soluble in acetone and ether. If ammonium chloride is mixed with strong bases - such as a sodium hydroxide solution or a potassium hydroxide solution - gaseous ammonia is released. If the crystalline solid is mixed with low-volatile, concentrated acids, such as sulphuric acid or phosphoric acid, hydrogen chloride is formed.
With an increase in temperature, ammonium chloride increasingly dissociates to form ammonia and hydrogen chloride. At 340 °C, the salt changes into the gaseous state. Ammonium chloride melts under pressure (34.4 bar) at 520 °C. In the laboratory, the salt is obtained by neutralising aqueous ammonia solution with hydrochloric acid or by the reaction of gaseous ammonia with gaseous hydrogen chloride. It also occurs as a by-product in the extraction of soda ash by the Solvay process.