Chemical Properties
Potassium bitartrate, also known as potassium hydrogen tartrate, 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.
Chemical Properties
Potassium Bitartrate, or tartar, is a salt produced from the crystalsfound on the sides of wine casks. When purified it is known as cream oftartar. It is acid, and is slightly soluble in water.It is used in baking powder, for medicine, and as an acid and buffer in foods.
Occurrence
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 , 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, 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. 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.
Uses
Potassium hydrogen tartrate [pH(S) = 3.639 / pH(S) = 3.557 (25 °C)] is a certified secondary standard reference buffer used as a calibration buffer standard for pH instruments or pH electrodes.
Uses
Potassium L-tartrate monobasic may be used as a reductant during the synthesis of noble metal nanoparticles in the presence of linear polymers as protective agents.
Uses
Largely in baking powders; coloring metals, galvanic tinning of metals; reducer of CrO3 in mordants for wool.
Application
In food
In food, potassium bitartrate is used for:
Stabilizing egg whites, increasing their heat tolerance and volume
Stabilizing whipped cream, maintaining its texture and volume
Preventing sugar syrups from crystallising
Reducing discolouration of boiled vegetables
Thickening Tartar sauce
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.
House hold use
Potassium bitartrate can be mixed with an acidic liquid such as lemon juice or white vinegar to make a paste - like cleaning agent for metals such as brass, aluminum or copper, or with water for other cleaning applications such as removing light stains from porcelain.
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. Cream of tartar was often used in traditional dyeing where the complexing action of the tartrate ions were used to adjust the solubility and hydrolysis of mordant salts such as tin chloride and alum.
Cream of tartar, when mixed into a paste with hydrogen peroxide, can be used to clean rust from some hand tools, notably hand files. The paste is applied and allowed to set for a few hours and then washed off with a baking soda/water solution.
Chemistry
Potassium acid tartrate, also known as potassium hydrogen tartrate, is, according to NIST, used as a primary reference standard for a pH buffer. .
Preparation
potassium bitartrate is mainly produced from the mother liquor of Seignette's salt. These decolorized, purified, and filtered solutions are acidified to pH 3.5 with hydrochloric or sulfuric acid. Since cream of tartar is sparingly soluble, it precipitates and is recovered by centrifugation, dried, and ground before being packaged as fine powder.
General Description
Potassium L-tartrate is found naturally in grapes. Its removal is necessary during wine making as it can precipitate, which is undesirable.
Purification Methods
It crystallises from water (17mL/g) between 100o and 0o. Dry it at 110o. [Beilstein 3 IV 1222.]
