C6H2HO3CO2H

Gallic Gal"lic (277), a. [From {Gall} the excrescence.] Pertaining to, or derived from, galls, nutgalls, and the like. [1913 Webster]

{Gallic acid} (Chem.), an organic acid, very widely distributed in the vegetable kingdom, being found in the free state in galls, tea, etc., and produced artificially. It is a white, crystalline substance, {C6H2(HO)3.CO2H}, with an astringent taste, and is a strong reducing agent, as employed in photography. It is usually prepared from tannin, and both give a dark color with iron salts, forming tannate and gallate of iron, which are the essential ingredients of common black ink. [1913 Webster]