1) An acid tartrate 2) Tartrate 
A bitartrate is a salt or monoester of tartaric acid. Examples include: ...
• (n.) A salt of tartaric acid in which the base replaces but half the acid hydrogen; an acid tartrate, as cream of tartar.
Bi·tar'trate noun (Chemistry) A salt of tartaric acid in which the base replaces but half the acid hydrogen; an acid tartrate, as cream of tartar. 
Type: Term Pronunciation: bī-tar′trāt Definitions: 1. A salt or anion resulting from the neutralization of one of tartaric acid's two acid groups.
[n] - an acid tartrate
noun an acid tartrate; a hydrogen tartrate
a tartrate in which only one of the two acidic hydrogen atoms of tartaric acid is replaced by a metal or positive group; an acid tartrate; a hydrogen tartrate, as sodium bitartrate.