Gallic acid is an organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts , sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C₆H₂(OH)₃CO₂H. Gallic acid is found both free and as part of tannins.

The COOH group has a pKa of 4.5, and the phenolic OHs have pKa 10.

External link

• King's American Dispensatory (1898) entry on Gallic acid