Alton Brown...on beating egg whites

***1/8 teaspoon of cream of tartar per egg white
***separate eggs when they are cold
***beat egg whites when they are at room temperature

Potassium bitartrate, also known as potassium hydrogen tartrate, has formula KC₄H₅O₆. It is a byproduct of winemaking.
In cooking it is known as cream of tartar. It is the potassium acid salt of tartaric acid.