Potassium bitartrate

Not to be confused with Tartar sauce.

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)
Y (verify) (what is: Y/N?) 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 a potassium acid salt of tartaric acid, a carboxylic acid (the other being potassium tartrate).

Occurrence

Potassium bitartrate crystallises in wine casks during the fermentation of grape juice, and can precipitate out of wine in bottles. The crystals 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, fresh grape juice should be chilled overnight to promote crystallisation. 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.

Applications

In food

In food, potassium bitartrate is used for:

• Stabilising egg whites, increasing their heat tolerance and volume
• Preventing sugar syrups from crystallising
• Reducing discolouration of boiled vegetables
• Stabilising whipped cream stiffness

Additionally it is used as a component of:

• Baking powder, as an acid ingredient to activate baking soda
• Sodium-free salt substitutes, in combination with potassium chloride

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

Household use

Potassium bitartrate can be used with white vinegar to make a paste-like cleaning agent.^{[citation needed]} 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.

It is a common ingredient in Play-Doh.^[3]

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.^[4]

See also

• Tartrate
• Tartaric acid
• Potassium tartrate (K₂C₄H₄O₆)

References

1. ^ Lloyds Vinyard FAQs
2. ^ National Center for Home Food Preservation
3. ^ Play Dough Recipes
4. ^ Harris, Daniel C. (17 July 2006), Quantitative Chemical Analysis (7th ed.), New York: W. H. Freeman, ISBN 978-0716776949 

External links

• Description of Potassium Bitartrate at Monash Scientific

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