Potassium bitartrate
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| Potassium bitartrate | |
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| 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 disclaimer and references |
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Potassium bitartrate also potassium hydrogen tartrate has formula KC4H5O6. It is a byproduct of winemaking. It is also known as cream of tartar. It is the potassium acid salt of tartaric acid.
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[edit] Occurrence
Potassium bitartrate crystallises in wine casks during the fermentation of grape juice. In wines bottled before they are fully ripe, it can precipitate on the side of the bottle in a sort of crust, thus forming what is called "crusted wine".
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.
[edit] Applications
[edit] 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, is confused with cream of tartar due to their similar function in baking powder.
[edit] Chemistry
Potassium acid tartrate, also known as potassium hydrogen tartrate, and according to NIST, is also used as a primary reference standard for a pH buffer. Using an excess of 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, potassium cation, and the tartrate dianion. 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° and 28°C.[1]
[edit] See also
[edit] External links
[edit] References
- This article incorporates text from the public domain 1911 edition of The Grocer's Encyclopedia.
- ^ Harris, Daniel C. Quantitative Chemical Analysis. Sixth Edition, W.H. Freeman and Company, New York, 2003.
