Potassium bitartrate

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 acid 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 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. 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. 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.