Potassium carbonate

Potassium carbonate

Names
IUPAC name Potassium carbonate
Other names Carbonate of potash, Dipotassium carbonate, Sub-carbonate of potash, Pearl ash, Potash, Salt of tartar, Salt of wormwood.
Identifiers
CAS Number	584-08-7
ChEBI	CHEBI:131526
ChemSpider	10949
Jmol 3D image	Interactive graph
PubChem	11430
RTECS number	TS7750000
UNII	BQN1B9B9HA
InChI InChI=1S/CH2O3.2K/c2-1(3)4;;/h(H2,2,3,4);;/q;2*+1/p-2 Key: BWHMMNNQKKPAPP-UHFFFAOYSA-L InChI=1/CH2O3.2K/c2-1(3)4;;/h(H2,2,3,4);;/q;2*+1/p-2 Key: BWHMMNNQKKPAPP-NUQVWONBAS
SMILES C(=O)([O-])[O-].[K+].[K+]
Properties
Chemical formula	K2CO3
Molar mass	138.205 g/mol
Appearance	white, hygroscopic solid
Density	2.43 g/cm^3
Melting point	891 °C (1,636 °F; 1,164 K)
Boiling point	decomposes
Solubility in water	112 g/100 mL (20 °C) 156 g/100 mL (100 °C)
Solubility	insoluble in alcohol, acetone
Hazards
Safety data sheet	ICSC 1588
GHS pictograms
GHS signal word	Warning
GHS hazard statements	H302, H315, H319, H335
GHS precautionary statements	P261, P305+351+338
EU classification (DSD)	Xn
R-phrases	R22 R36 R37 R38
NFPA 704	0 1 0
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	1870 mg/kg (oral, rat)[1]
Related compounds
Other anions	Potassium bicarbonate
Other cations	Lithium carbonate Sodium carbonate Rubidium carbonate Caesium carbonate
Related compounds	Ammonium 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

Potassium carbonate (K₂CO₃) is a white salt, soluble in water (insoluble in ethanol)^[2] which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid. Potassium carbonate is used in the production of soap and glass.

History

Potassium carbonate is the primary component of potash and the more refined pearl ash or salts of tartar. Historically, pearl ash was created by baking potash in a kiln to remove impurities. The fine, white powder remaining was the pearl ash. The first patent issued by the US Patent Office was awarded to Samuel Hopkins in 1790 for an improved method of making potash and pearl ash.

In late 18th century North America, before the development of baking powder, pearl ash was used as a leavening agent in quick breads.^[3]

Production

Today, potassium carbonate is prepared commercially by the electrolysis of potassium chloride. The resulting potassium hydroxide is then carbonated using carbon dioxide to form potassium carbonate, which is often used to produce other potassium compounds.

2KOH + CO₂ → K₂CO₃ + H₂O

Applications

• (historically) for soap, glass, and china production
• as a mild drying agent where other drying agents, such as calcium chloride and magnesium sulfate, may be incompatible. It is not suitable for acidic compounds, but can be useful for drying an organic phase if one has a small amount of acidic impurity. It may also be used to dry some ketones, alcohols, and amines prior to distillation.^[4]
• In cuisine, it is used as an ingredient in the production of grass jelly, a food consumed in Chinese and Southeast Asian cuisines. It is used to tenderize tripe. German gingerbread recipes often use potassium carbonate as a baking agent.
• Used in the production of cocoa powder to balance the pH (i.e. reduce the amount of acidity) of natural cocoa beans (it also helps enhance the aroma). The process of adding potassium carbonate to cocoa powder is usually called "Dutching", or Dutch-processed cocoa powder, as the process was first developed in 1828 by Coenrad Johannes van Houten, a Dutchman.
• as a buffering agent in the production of mead or wine.
• softening hard water.^[5]
• as a fire suppressant in extinguishing deep-fat fryers and various other B class-related fires
• in condensed aerosol fire suppression, although as the byproduct of potassium nitrate.
• an ingredient in welding fluxes, and in the flux coating on arc-welding rods.
• stability in neurons to help maintain equilibrium.
• as an animal feed ingredient to satisfy the potassium requirements of farmed animals such as broiler breeders

References

1. http://chem.sis.nlm.nih.gov/chemidplus/rn/584-08-7
2. http://www.researchgate.net/publication/231535294_Solubility_of_Potassium_Carbonate_and_Potassium_Hydrocarbonate_in_Methanol),
3. See references to "pearl ash" in "American Cookery" by Amelia Simmons, printed by Hudson & Goodwin, Hartford, 1796.
4. Leonard, J.; Lygo, B.; Procter, G. "Advanced Practical Organic Chemistry" 1998, Stanley Thomas Publishers Ltd
5. Child, Lydia M. "The American Frugal Housewife" 1832

Bibliography

A Dictionary of Science, Oxford University Press, New York, 2004

External links

• International Chemical Safety Card 1588