- a white or yellowish, crystalline, sparingly water-soluble solid, C7H6O5, obtained from nutgalls, used chiefly in tanning and in ink dyes.
- a colourless crystalline compound obtained from tannin: used as a tanning agent and in making inks, paper, and pyrogallol; 3,4,5-trihydroxybenzoic acid. Formula: C 6 H 2 (OH) 3 COOH
