gallic acid

gallic acid
a white or yellowish, crystalline, sparingly water-soluble solid, C7H6O5, obtained from nutgalls, used chiefly in tanning and in ink dyes.
[1785-95; < F acide gallique]

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      substance occurring in many plants, either in the free state or combined as gallotannin. It is present to the extent of 40–60 percent combined as gallotannic acid in tara (any of various plants of the genus Caesalpinia) and in Aleppo and Chinese galls (swellings of plant tissue), from which it is obtained commercially by the action of acids or alkalies. An Aleppo gall has a spherical shape, is hard and brittle, and is about the size of a hickory nut; it is produced on oak twigs by a gall wasp (Cynips tinctoria). A Chinese gall is produced by insects on Asian sumac (Rhus semialata).

      When heated to 200°–250° C, gallic acid splits into carbon dioxide and pyrogallol (pyrogallic acid), the photographic developer. With iron salts it gives a deep blue-black colour, the basis of writing ink. It is used in the manufacture of a few dyes. As bismuth subgallate it has been employed in medicine as a mild skin antiseptic and astringent (q.v.; an agent that tends to shrink mucous membranes and raw surfaces and to dry up secretions). Propyl gallate is an important antioxidant for the prevention of rancidity in edible oils and fats. Gallic acid is 3,4,5-trihydroxybenzoic acid and has the formula (HO)3C6H2·CO2H.

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Universalium. 2010.

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Look at other dictionaries:

  • Gallic acid — IUPAC name …   Wikipedia

  • Gallic acid — 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… …   The Collaborative International Dictionary of English

  • gallic acid — n. [Fr gallique < galle, GALL3] a nearly colorless, crystalline acid, (OH) 3C6H2COOH, prepared from tannins, etc. and used in photography and the manufacture of inks, dyes, etc …   English World dictionary

  • gallic acid — galo rūgštis statusas T sritis chemija formulė (HO)₃C₆H₂COOH atitikmenys: angl. gallic acid rus. галловая кислота ryšiai: sinonimas – 3,4,5 trihidroksibenzenkarboksirūgštis …   Chemijos terminų aiškinamasis žodynas

  • gallic acid — Usually made from tannic acid or nutgalls; used locally as an astringent, for the same purpose as tannic acid. * * * gal·lic acid .gal ik , .gȯ lik n a white crystalline acid C7H6O5 found widely in plants or combined in tannins and used esp. in… …   Medical dictionary

  • gallic acid — noun a) a phenolic carboxylic acid, 3,4,5 trihydroxybenzoic acid, found in galls, tea, the bark of some trees etc; a constituent of tannin b) the supposed acid HGaO, the acid form of the amphoteric gallium hydroxide Ga(OH), known only as alkali… …   Wiktionary

  • gallic acid — (= 3,4,5 trihydroxybenzoic acid) Phenolic acid, commonly found in flowering plants, usually esterified with tannins …   Dictionary of molecular biology

  • gallic acid — noun Etymology: French gallique, from galle gall Date: 1788 a white crystalline acid C7H6O5 found widely in plants or combined in tannins and used especially in dyes and as a photographic developer …   New Collegiate Dictionary

  • gallic acid — noun Chemistry an organic acid extracted from oak galls and other plant products. Origin C18: from L. galla (see gall3) + ic …   English new terms dictionary

  • gallic acid — /gælɪk ˈæsəd/ (say galik asuhd) noun a complex phenolic acid, C6H2(OH)3CO2H, a white or yellowish crystalline powder found in nut galls, mangoes, and other plants …  

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