Potassium carbonate

Potassium carbonate
IUPAC name
Potassium carbonate
Other names
Carbonate of potash, dipotassium carbonate, sub-carbonate of potash, pearl ash, potash, salt of tartar, salt of wormwood.
3D model (JSmol)
ECHA InfoCard 100.008.665 Edit this at Wikidata
E number E501(i) (acidity regulators, ...)
RTECS number
  • TS7750000
  • InChI=1S/CH2O3.2K/c2-1(3)4;;/h(H2,2,3,4);;/q;2*+1/p-2 checkY
  • InChI=1/CH2O3.2K/c2-1(3)4;;/h(H2,2,3,4);;/q;2*+1/p-2
  • C(=O)([O-])[O-].[K+].[K+]
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
110.3g/100 mL (20°C)
149.2g/100 mL (100°C)
Acidity (pKa) 10.25
114.4 J·mol−1·K−1
155.5 J·mol−1·K−1
−1151.0 kJ·mol−1
−1063.5 kJ·mol−1
Enthalpy of fusion fHfus)
27.6 kJ·mol−1
GHS labelling:
GHS07: Exclamation mark
H302, H315, H319, H335
P261, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
1870mg/kg (oral, rat)
Safety data sheet (SDS) ICSC 1588
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 is the inorganic compound with the formula K2CO3. It is a white salt, which is soluble in water and forms a strongly alkaline solution. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and glass.


Potassium carbonate is the primary component of potash and the more refined pearl ash or salts of tartar. 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.


Potassium lye (which in this case can alternatively be called potash), a substance which contains potassium carbonate, potassium bicarbonate, and potassium hydroxide, was historically produced by dissolving the lye found in the wooden ashes inside of water for app one or more days, disposing of the undissolved ashes, and then drying/evaporating the remaining liquid.

With modern observation, this process would produce greater yields if done with the ashes of banana peels due to their increased amounts of potassium carbonate.

As previously mentioned, Samuel Hopkins created an improved method of making pearl ash. One of those procedures was putting the lye/potash in a kiln to remove impurities.

Potassium carbonate is today, prepared commercially, by the reaction of potassium hydroxide with carbon dioxide:

2 KOH + CO2 → K2CO3 + H2O

From the solution crystallizes the sequestrate K2CO3·32H2O ("potash hydrate"). Heating this solid above 200 °C (392 °F) 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


This page was last updated at 2023-11-01 08:40 UTC. Update now. View original page.

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