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 powder can be used in baking or as a cleaning solution (when mixed with an acidic solution such as lemon juice or white vinegar). History Potassium bitartrate was first characterized by Swedish chemist Karl Wilhelm Scheele (1742-1786). This was a result of Scheele's work studying fluorite and hydrofluoric acid. Scheele may have been the first scientist to publish work on potassium bitartrate, but use of potassium bitartrate has been reported to date back 7000 years to an ancient village in northern Iran. Modern applications of cream of tartar started in 1768 after it gained popularity when the French started using it regularly in their cuisine. Occurrence Potassium bitartrate is naturally formed in grapes from the acid dissociation of tartaric acid into bitartrate and tartrate ions. Potassium bitartrate has a low solubility in water. It crystallizes in wine casks during the fermentation of grape juice, and can precipitate out of wine in bottles. The rate of potassium bitartrate precipitation depends on the rates of nuclei formation and crystal growth, which varies based on a wine's alcohol, sugar, and extract content. The crystals (wine diamonds) will often form on the underside of a cork in wine-filled bottles that have been stored at temperatures below , and will seldom, if ever, dissolve naturally into the wine. Over time, crystal formation is less likely to occur due to the decreasing supersaturation of potassium bitartrate, with the greatest amount of precipitation occurring in the initial few days of cooling. Historically, it was known as beeswing for its resemblance to the sheen of bees' wings. It was collected and purified to produce the white, odorless, acidic powder used for many culinary and other household purposes. These crystals also precipitate out of fresh grape juice that has been chilled or allowed to stand for some time. To prevent crystals from 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