Gallic acid

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Gallic acid

IUPAC name	3,4,5-hydroxybenzoic acid
Other names	Gallic acid
Identifiers
CAS number	[149-91-7] (Anhydrous) [5995-86-8] (Monohydrate)
SMILES	Oc1cc(cc(O)c1O)C(O)=O
Properties
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 (pK_a)	COOH: 4.5, OH: 10.
Hazards
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)₃COOH. Gallic acid is found both free and as part of tannins. Salts and esters of gallic acid are termed gallates. Despite its name, it does not contain gallium.

Gallic acid is commonly used in the pharmaceutical industry.^{[citation needed]} It is used as a standard for determining the phenol content of various analytes by the Folin-Ciocalteau assay; results are reported in gallic acid equivalents.^[1] Gallic acid can also be used to synthesize the hallucinogenic alkaloid mescaline, also known as 3,4,5-trimethoxyphenethylamine.^{[citation needed]}

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.^{[citation needed]}