potassium bitartrate

Potassium bitartrate
Other names	potassium hydrogen tartrate cream of tartar potassium acid tartrate monopotassium tartrate
Identifiers
CAS number	868-14-4
Properties
Molecular formula	KC4H5O6
Molar mass	188.177
Appearance	white crystalline powder
Density	1.05 g/cm3 (solid)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Potassium bitartrate, also known as potassium hydrogen tartrate, has formula KC₄H₅O₆. It is a byproduct of winemaking. In cooking it is known as cream of tartar. It is the potassium acid salt of tartaric acid, a carboxylic acid.

Occurrence

Potassium bitartrate crystallises in wine casks during the fermentation of grape juice, and can precipitate out of wine in bottle.

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

Applications

In food

In food, potassium bitartrate is used for:

• Stabilizing egg whites, increasing their heat tolerance and volume;
• Preventing sugar syrups from crystallising;
• Reducing discolouration of boiled vegetables;
• Frequent combination with baking soda (which needs an acid ingredient to activate it) in formulations of baking powder.
• Commonly used in combination with potassium chloride in sodium-free salt substitutes

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

Household use

Potassium bitartrate can be used with white vinegar to make a paste-like cleaning agent. It is a vital ingredient in Play-Doh and gingerbread house icing. This mixture is sometimes mistakenly made with vinegar and sodium bicarbonate (baking soda), which actually react to neutralise each other, creating carbon dioxide and a sodium acetate solution.

Chemistry

Potassium acid tartrate, also known as potassium hydrogen tartrate, is according to NIST used as a 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. 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 and 28 °C.^[1]

See also

• Tartrate
• Tartaric acid
• Potassium tartrate

External links

• Description of Potassium Bitartrate at Monash Scientific

References

This article incorporates text from the public domain 1911 edition of The Grocer's Encyclopedia.

1. ^ Harris, Daniel C. (17 July 2006), Quantitative Chemical Analysis (7th ed.), New York: W. H. Freeman, ISBN 978-0716776949