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 Y 6381-79-9 sesquihydrate
3D model (JSmol)	Interactive image
ChEBI	CHEBI:131526 N
ChemSpider	10949 Y
ECHA InfoCard	100.008.665
E number	E501(i) (acidity regulators, ...)
PubChem CID	11430
RTECS number	TS7750000
UNII	BQN1B9B9HA Y
CompTox Dashboard (EPA)	DTXSID2036245
InChI InChI=1S/CH2O3.2K/c2-1(3)4;;/h(H2,2,3,4);;/q;2*+1/p-2 Y Key: BWHMMNNQKKPAPP-UHFFFAOYSA-L Y 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
Molar mass	138.205 g/mol
Appearance	White, hygroscopic solid
Density	2.43g/cm3
Melting point	891 °C (1,636 °F; 1,164 K)
Boiling point	Decomposes
Solubility in water	110.3g/100 mL (20°C) 149.2g/100 mL (100°C)
Solubility	3.11g/100 mL (25°C) methanol Insoluble in alcohol, acetone
Magnetic susceptibility (χ)	-59.0·10-6cm3/mol
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
NFPA 704 (fire diamond)	0 1 0
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1870mg/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).
N verify (what is YN ?)
Infobox references

Potassium carbonate is the inorganic compound with the formula K₂CO₃. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and glass.^[2]

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 for quick breads.^[3][4]

Production

Potassium carbonate is prepared commercially by the reaction potassium hydroxide with carbon dioxide:^[2]

2 KOH + CO₂ → K₂CO₃ + H₂O

From the solution crystallizes the sesquihydrate K₂CO₃·​H₂O ("potash hydrate"). Heating this solid above 200 °C gives the anhydrous salt. In an alternative method, potassium chloride is treated with carbon dioxide in the presence of an organic amine to give potassium bicarbonate, which is then calcined:

2 KHCO₃ → K₂CO₃ + H₂O + CO₂

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.^[5]
• in cuisine, where it has many traditional uses. It is an ingredient in the production of grass jelly, a food consumed in Chinese and Southeast Asian cuisines, as well as Chinese hand-pulled noodles and moon cake. It is also used to tenderize tripe. German gingerbread recipes often use potassium carbonate as a baking agent, although in combination with hartshorn. Use of potassium carbonate must be limited to a certain amount to prevent harm, and should not be used without guidance.
• in the alkalization of cocoa powder to produce Dutch process chocolate by balancing the pH (i.e., reduce the acidity) of natural cocoa beans; it also enhances aroma. The process of adding potassium carbonate to cocoa powder is usually called "Dutching" (and the products referred to as Dutch-processed cocoa powder), as the process was first developed in 1828 by Dutchman Coenraad Johannes van Houten.
• as a buffering agent in the production of mead or wine.
• in antique documents, it is reported to have been used to soften hard water.^[6]
• 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.
• as an ingredient in welding fluxes, and in the flux coating on arc-welding rods.
• as an animal feed ingredient to satisfy the potassium requirements of farmed animals such as broiler breeders.
• as an acidity regulator in Swedish snus

References

Bibliography

• A Dictionary of Science, Oxford University Press, New York, 2004
• Yu. Platonov, Andrew; Evdokimov, Andrey; Kurzin, Alexander; D. Maiyorova, Helen (29 June 2002). "Solubility of Potassium Carbonate and Potassium Hydrocarbonate in Methanol". Journal of Chemical & Engineering Data. 47 (5): 1175-1176. doi:10.1021/je020012v.

External links

• International Chemical Safety Card 1588