Ammonium carbonate

Product Description

Name: Ammonium carbonate
CAS Registry Number: 506-87-6

Ammonium carbonate is the commercial salt, formerly known as sal volatile or salt of hartshorn. Ammonium carbonate is used when crushed as a smelling salt. It can be crushed when needed in order to revive someone who has fainted. It is also known as "baker's ammonia" and was a forerunner to the more modern leavening agents baking soda and baking powder.
Ammonium carbonate was historically obtained by the dry distillation of nitrogenous organic matter such as hair, horn, decomposed urine, etc.[citation needed]
Currently, it is produced by heating a mixture of ammonium chloride, or ammonium sulfate and chalk, to redness in iron retorts, the vapors being condensed in leaden receivers.[citation needed] The crude product is refined by sublimation, when it is obtained as a white fibrous mass, which consists of a mixture of ammonium bicarbonate, NH4HCO3, and ammonium carbonate, (NH4)2CO3, in molecular proportions; on account of its possessing this constitution it is sometimes called ammonium polycarbonate. It possesses a strong ammonium smell, and on digestion with alcohol the carbonate is dissolved and a residue of ammonium bicarbonate is left; a similar decomposition taking place when the polycarbonate is exposed to air.
Ammonia gas passed into a strong aqueous solution of the polycarbonate converts it into normal ammonium carbonate, (NH4)2CO3, which can be obtained in the crystalline condition from a solution prepared at about 30 °C. This compound on exposure to air gives off ammonia and passes back to ammonium bicarbonate. It has pH of 9.