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Gallic acid

Gallic acid
IUPAC name 3,4,5-hydroxybenzoic acid
Other names Gallic acid
CAS number [149-91-7] (Anhydrous)
[5995-86-8] (Monohydrate)
SMILES Oc1cc(cc(O)c1O)C(O)=O
Molecular formula C7H6O5
Molar mass 170.12 g/mol
Appearance White, yellowish-white, or
pale fawn-colored crystals.
Density 1.7 g/cm3 (anhydrous)
Melting point

250°C (523 K)

Boiling point

(? K)

Solubility in water 1.1g/100ml water @ 20°C (anhydrous)
1.5g/100ml water @ 20°C (monohydrate)
Acidity (pKa) COOH: 4.5, OH: 10.
MSDS External MSDS
Main hazards Irritant
Related Compounds
Related compounds Benzoic acid, Phenol
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

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. It is commonly used in the pharmaceutical industry. Gallic acid can also be used to synthesize the hallucinogenic alkaloid mescaline, also known as 3,4,5-trimethoxyphenethylamine.

Salts and esters of gallic acid are termed gallates.

Gallic acid was one of the substances used by Angelo Mai among other early investigators of palimpsests to clear the top layer of text off and reveal hidden manuscripts underneath. Mai was the first to employ it, but did so "with a heavy hand," often damaging manuscripts for future study.

See also


  • LD Reynolds and NG Wilson, “Scribes and Scholars” 3rd Ed. Oxford: 1991. pp193–4.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Gallic_acid". A list of authors is available in Wikipedia.
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