Potassium Hydrogen Tartrate

Potassium hydrogen tartrate is known by a variety of names including potassium bitartrate, potassium acid tartrate, cream of tartar, and faeccula. An impure form of potassium hydrogen tartrate, called argol, is formed naturally during the fermentation of a variety of fruit juices. It is found as a crystal residue in wine casks.

One gram of potassium hydrogen tartrate dissolves in 162 ml water. When the water temperature is increased, so is its solubility. Using boiling water, one gram will dissolve in about 16 ml of water. The material is insoluble in absolute alcohol. The saturated aqueous solution has a pH of approximately 3.5. In this solution the material dissociates into its component ions, one of which is tartaric acid. This acid was first isolated and characterized in 1769 by chemist Carl Wilhelm Scheele. He obtained it by boiling cream of tartar with chalk and then treating it with sulfuric acid.