Cream of tartar

Commercial cream of tartar, used in baking, is the acid potassium salt of tartaric acid that has been refined, bleached, and turned into a powder. Cream of tartar is used in manufacturing chemical leavening agents, such as baking powder, to release carbon dioxide; it is also used to inhibit recrystallization in candies and syrups and to help stiffen egg whites for meringues.