Ammonium carbonate

Ammonium carbonate

Names
IUPAC name Ammonium carbonate
Other names baker's ammonia sal volatile salt of hartshorn E503
Identifiers
CAS Number	506-87-6
ChemSpider	10048
IUPHAR/BPS	4509
Jmol 3D model	Interactive image
UNII	PDP691CN28
InChI InChI=1S/CH2O3.2H3N/c2-1(3)4;;/h(H2,2,3,4);2*1H3 Key: PRKQVKDSMLBJBJ-UHFFFAOYSA-N InChI=1/CH2O3.2H3N/c2-1(3)4;;/h(H2,2,3,4);2*1H3 Key: PRKQVKDSMLBJBJ-UHFFFAOYAQ
SMILES O=C(O)O.N.N
Properties
Chemical formula	(NH4)2CO3
Molar mass	96.09 g/mol
Appearance	White powder
Density	1.50 g/cm^3
Melting point	58 °C (136 °F; 331 K)
Boiling point	Decomposes
Solubility in water	Soluble, decomposes in hot water
Hazards
Main hazards	Xi
Safety data sheet	External MSDS
Related compounds
Other anions	Ammonium bicarbonate
Other cations	Sodium carbonate Potassium carbonate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Ammonium carbonate is a salt with the chemical formula (NH₄)₂CO₃. Commercial samples labelled ammonium carbonate no longer contain this compound, but a mixture that has similar ammonia content. Since it readily degrades to gaseous ammonia and carbon dioxide upon heating, it is used as a leavening agent and also as smelling salt. It is also known as baker's ammonia and was a predecessor to the more modern leavening agents baking soda and baking powder. It is a component of what was formerly known as sal volatile and salt of hartshorn.^[1]

Production

Ammonium carbonate is produced by combining carbon dioxide and aqueous ammonia. About 7000 tons/year were produced as of 1997.^[1]

Decomposition

Ammonium carbonate slowly decomposes at standard temperature and pressure through two pathways. Thus any initially "pure" sample of ammonium carbonate will soon become a mixture including various byproducts.

Ammonium carbonate can spontaneously decompose into ammonium bicarbonate and ammonia:

(NH₄)₂CO₃ → NH₄HCO₃ + NH₃

Uses

Leavening agent

Ammonium carbonate may be used as a leavening agent in traditional recipes, particularly those from northern Europe and Scandinavia (e.g. Speculoos, Tunnbröd or Lebkuchen). It also serves as an acidity regulator and has the E number E503. It can be substituted with baking powder, but this may affect both the taste and texture of the finished product.

Its use as a leavening agent, with associated controversy, goes back centuries:

In the third kind of bread, a vesicular appearance is given to it by the addition to the dough of some ammoniacal salt, (usually the sub-carbonate,) which becomes wholly converted into a gaseous substance during the process of baking, causing the dough to swell out into little air vessels, which finally bursting, allow the gas to escape, and leave the bread exceedingly porous. Mr. Accum, in his Treatise on Culinary Poisons, has stigmatized this process as "fraudulent," but, in our opinion, most unjustly. The bakers would never adopt it but from necessity: when good yeast cannot be procured, it forms an admirable and perfectly harmless substitute; costing the baker more, it diminishes his profit, while the consumer is benefited by the bread retaining the solid matter, which by the process of fermentation is dissipated in the form of alcohol and carbonic acid gas.^[2]

Other uses

Ammonium carbonate is the main component of smelling salts, although the commercial scale of their production is small. Buckley's cough syrup from Canada today uses ammonium carbonate as an active ingredient intended to help relieve symptoms of bronchitis. It is also used as an emetic. It is also found in smokeless tobacco products, such as Skoal.

See also

• Sal ammoniac, the mineralogical form of ammonium chloride
• Ammonium nitrate

References

1. Karl-Heinz Zapp "Ammonium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2012, Wiley-VCH, Weinheim. doi:10.1002/14356007.a02_243
2. "Bread". The Engineer's and Mechanic's Encyclopedia 1. Luke Hebert. 1849. p. 239.