Potassium bitartrate

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Potassium bitartrate
Potassium bitartrate
Preferred IUPAC name
  • Potassium (2R,3R)-2,3,4-trihydroxy-4-oxobutanoate
Other names
  • Potassium hydrogen tartrate
  • Cream of tartar
  • Potassium acid tartrate
  • Monopotassium tartrate
  • Beeswing
3D model (JSmol)
ECHA InfoCard 100.011.609 Edit this at Wikidata
E number E336 (antioxidants, ...)
  • InChI=1S/C4H6O6.K/c5-1(3(7)8)2(6)4(9)10;/h1-2,5-6H,(H,7,8)(H,9,10);/q;+1/p-1/t1-,2-;/m1./s1 ☒N
  • InChI=1/C4H6O6.K/c5-1(3(7)8)2(6)4(9)10;/h1-2,5-6H,(H,7,8)(H,9,10);/q;+1/p-1/t1-,2-;/m1./s1
  • [C@@H]([C@H](C(=O)[O-])O)(C(=O)O)O.[K+]
Molar mass 188.177
Appearance White crystalline powder
Density 1.05 g/cm3 (solid)
  • 0.57 g/100 ml (20 °C)
  • 6.1 g/100 ml (100 °C)
Solubility Soluble in acid, alkali
Insoluble in acetic acid, alcohol
A12BA03 (WHO)
Lethal dose or concentration (LD, LC):
22 g/kg (oral, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potassium bitartrate, also known as potassium hydrogen tartrate, with formula KC4H5O6, is a byproduct of winemaking. In cooking, it is known as cream of tartar. It is processed from the potassium acid salt of tartaric acid (a carboxylic acid). The resulting powdery base can be used in baking or as a cleaning solution (when mixed with an acidic solution such as lemon juice or white vinegar).


Potassium bitartrate in an empty white wine bottle

Potassium bitartrate has a low solubility in water. It crystallizes in wine casks during the fermentation of grape juice, and can precipitate out of wine in bottles. The crystals (wine diamonds) will often form on the underside of a cork in wine-filled bottles that have been stored at temperatures below 10 °C (50 °F), and will seldom, if ever, dissolve naturally into the wine.

These crystals also precipitate out of fresh grape juice that has been chilled or allowed to stand for some time.[1] To prevent crystals forming in homemade grape jam or jelly, the prerequisite fresh grape juice should be chilled overnight to promote crystallization. The potassium bitartrate crystals are removed by filtering through two layers of cheesecloth. The filtered juice may then be made into jam or jelly.[2] In some cases they adhere to the side of the chilled container, making filtering unnecessary.

The crude form (known as beeswing) is collected and purified to produce the white, odorless, acidic powder used for many culinary and other household purposes.


In food[edit]

Folger's Golden Gate Cream Tartar, first half of 20th century

In food, potassium bitartrate is used for:

Additionally, it is used as a component of:

A similar acid salt, sodium acid pyrophosphate, can be confused with cream of tartar because of its common function as a component of baking powder.

Household use[edit]

Potassium bitartrate can be mixed with an acidic liquid such as lemon juice or white vinegar to make a paste-like cleaning agent for metals such as brass, aluminium, or copper, or with water for other cleaning applications such as removing light stains from porcelain.[8] This mixture is sometimes mistakenly made with vinegar and sodium bicarbonate (baking soda), which actually react to neutralize each other, creating carbon dioxide and a sodium acetate solution.

Cream of tartar was often used in traditional dyeing where the complexing action of the tartrate ions was used to adjust the solubility and hydrolysis of mordant salts such as tin chloride and alum.

Cream of tartar, when mixed into a paste with hydrogen peroxide, can be used to clean rust from some hand tools, notably hand files. The paste is applied and allowed to set for a few hours and then washed off with a baking soda/water solution. After another rinse with water and thorough drying, a thin application of oil will protect the file from further rusting.

Slowing the set time of plaster of Paris products (most widely used in gypsum plaster wall work and artwork casting) is typically achieved by the simple introduction of almost any acid diluted into the mixing water. A commercial retardant premix additive sold by USG to trade interior plasterers includes at least 40% potassium bitartrate. The remaining ingredients are the same plaster of Paris and quartz-silica aggregate already prominent in the main product. This means that the only active ingredient is the cream of tartar.[9]


For dyeing hair, potassium bitartrate can be mixed with henna as the mild acid needed to activate the henna.

Medicinal use[edit]

Cream of tartar has been used internally as a purgative, but this is dangerous because an excess of potassium, or hyperkalemia, may occur.[10][citation needed]


Potassium bitartrate is the United States' National Institute of Standards and Technology's primary reference standard for a pH buffer. Using an excess of the salt in water, a saturated solution is created with a pH of 3.557 at 25 °C (77 °F). Upon dissolution in water, potassium bitartrate will dissociate into acid tartrate, tartrate, and potassium ions. Thus, a saturated solution creates a buffer with standard pH. Before use as a standard, it is recommended that the solution be filtered or decanted between 22 °C (72 °F) and 28 °C (82 °F).[11]

Potassium carbonate can be made by burning cream of tartar, which produces "pearl ash". This process is now obsolete but produced a higher quality (reasonable purity) than "potash" extracted from wood or other plant ashes.


See also[edit]


  1. ^ Max Williams at McNicol Williams Management & Marketing Services. "Lloyds Vineyard FAQs". Lloydsvineyard.com.au. Archived from the original on 15 December 2011. Retrieved 19 April 2018.
  2. ^ "National Center for Home Food Preservation". Uga.edu. Retrieved 19 April 2018.
  3. ^ The science of good cooking : master 50 simple concepts to enjoy a lifetime of success in the kitchen (1st ed.). America's Test Kitchen. 2012. p. 199. ISBN 978-1-933615-98-1.
  4. ^ "How to Use Cream of Tartar". wikiHow. Archived from the original on 28 May 2019. Retrieved 28 May 2019.
  5. ^ Stephens, Emily (18 February 2017). "The Incredible Cream of Tartar – How to Use and What to Substitute With". MyGreatRecipes. Retrieved 28 May 2019.
  6. ^ Provost, Joseph J.; Colabroy, Keri L.; Kelly, Brenda S.; Wallert, Mark A. (2016). The Science of Cooking : Understanding the Biology and Chemistry Behind Food and Cooking. John Wiley and Sons, Inc. p. 504. ISBN 9781118674208.
  7. ^ McGee, Harold (2004). On food and cooking : the science and lore of the kitchen (2nd ed.). Scribner. p. 533,534. ISBN 978-0-684-80001-1.
  8. ^ "Michigan State University Extension Home Maintenance And Repair – Homemade Cleaners – 01500631, 06/24/03". Archived from the original on 23 June 2009. Retrieved 19 April 2018.
  9. ^ "Material Safety Data Sheet: Gypsum Plaster Retarder for Lime-Based Products" (PDF). USG Inc. Archived from the original (PDF) on 29 August 2016. Retrieved 21 July 2016.
  10. ^ Rusyniak, Daniel E.; Durant, Pamela J.; Mowry, James B.; Johnson, Jo A.; Sanftleben, Jayne A.; Smith, Joanne M. (2013). "Life-Threatening Hyperkalemia from Cream of Tartar Ingestion". Journal of Medical Toxicology. 9 (1): 79–81. doi:10.1007/s13181-012-0255-x. PMC 3570668. PMID 22926733.
  11. ^ Harris, Daniel C. (17 July 2006), Quantitative Chemical Analysis (7th ed.), New York: W. H. Freeman, ISBN 978-0-7167-7694-9

External links[edit]