Potassium carbonate

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.[4][5]

In late 18th-century North America, before the development of baking powder, pearl ash was used as a leavening agent for quick breads.[6][7]

Potassium lye (which in this case can alternatively be called potash), a substance which contains potassium carbonate, potassium bicarbonate, and potassium hydroxide,[8][9] 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.[8][10]

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.[10]

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:[3]

2 KOH + CO₂ → K₂CO₃ + H₂O

From the solution crystallizes the sequestrate K₂CO₃·3⁄2H₂O ("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

• (historically) for soap, glass, and dishware 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.[11]
• in cuisine, where it has many traditional uses. It is used in some types of Chinese noodles and mooncakes, as well as Asian grass jelly and Japanese ramen. German gingerbread recipes often use potassium carbonate as a baking agent, although in combination with hartshorn.
• 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.[12]
• 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 breeder chickens.
• as an acidity regulator in Swedish snus snuff tobacco

• 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.

• International Chemical Safety Card 1588