ammonium carbonate

Ammonium carbonate
IUPAC name	Ammonium carbonate
Identifiers
CAS number	506-87-6 Y
SMILES	O=C(O)O.N.N
InChI	1/CH2O3.2H3N/c2-1(3)4;;/h(H2,2,3,4);2*1H3
InChI key	PRKQVKDSMLBJBJ-UHFFFAOYAQ
ChemSpider ID	10048
Properties
Molecular formula	(NH4)2CO3
Molar mass	96.09 g/mol
Appearance	White powder
Density	1.50 g/cm3
Melting point	58 °C
Boiling point	Decomposes
Solubility in water	Soluble, decomposes in hot water
Hazards
MSDS	External MSDS
Main hazards	Irritant
Related compounds
Other anions	Ammonium bicarbonate
Other cations	Sodium carbonate Potassium carbonate
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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.

Production

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.

Uses

As well as in smelling salts, ammonium carbonate is still used as a leavening agent in particular recipes, particular northern European and Scandinavian. It can sometimes be substituted with baking powder, but the finished product will never be as airy and light as the original recipe. Icelandic loftkökur (air biscuits) for instance simply cannot be made with anything other than ammonium carbonate.

Buckleys cough syrup from Canada also uses ammonium carbonate as an active ingredient intended to help relieve symptoms of bronchitis.

See also

• Smelling salts

References

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