| Potassium bitartrate | |
|---|---|
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Other names
potassium hydrogen tartrate |
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| Identifiers | |
| CAS number | 868-14-4 |
| Properties | |
| Molecular formula | KC4H5O6 |
| Molar mass | 188.177 |
| Appearance | white crystalline powder |
| Density | 1.05 g/cm3 (solid) |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Potassium hydrogen tartrate, also known as Potassium bitartrate, has formula KC4H5O6, 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.
Contents |
Potassium bitartrate 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, 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.
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 their common function as a component of baking powder.
Potassium bitartrate can be used with white vinegar to make a paste-like cleaning agent. 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]
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]