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|Section2= |Section3= |Section7= |Section8= }} Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants.〔LD Reynolds and NG Wilson, "Scribes and Scholars" 3rd Ed. Oxford: 1991. pp193–4.〕 The chemical formula is C6H2(OH)3COOH. Gallic acid is found both free and as part of hydrolyzable tannins. The gallic acid groups are usually bonded to form dimers such as ellagic acid. Hydrolysable tannins break down on hydrolysis to give gallic acid and glucose or ellagic acid and glucose, known as gallotannins and ellagitannins respectively. Gallic acid forms intermolecular esters (depsides) such as digallic and trigallic acid, and cyclic ether-esters (depsidones). 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. 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''.〔(【引用サイトリンク】 Folin-Ciocalteau Micro Method for Total Phenol in Wine )〕 Gallic acid can also be used as a starting material in the synthesis of the psychedelic alkaloid mescaline. == Historical context and uses == Gallic acid is an important component of iron gall ink, the standard European writing and drawing ink from the 12th to 19th century with a history extending to the Roman empire and the Dead Sea Scrolls. Pliny the Elder (23-79 AD) describes his experiments with it and writes that it was used to produce dyes. Galls (also known as oak apples) from oak trees were crushed and mixed with water, producing tannic acid. It could then be mixed with green vitriol (ferrous sulfate) — obtained by allowing sulfate-saturated water from a spring or mine drainage to evaporate — and gum arabic from acacia trees; this combination of ingredients produced the ink.〔(【引用サイトリンク】first=Lois )〕 Gallic acid was one of the substances used by Angelo Mai (1782–1854), 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 rendering manuscripts too damaged for subsequent study by other researchers. Gallic acid was first studied by the Swedish chemist Carl Wilhelm Scheele in 1786.〔Carl Wilhelm Scheele (1786) ("Om Sal essentiale Gallarum eller Gallåple-salt" ) (On the essential salt of galls or gall-salt), ''Kongliga Vetenskaps Academiens nya Handlingar'' (Proceedings of the Royal () Academy of Science), vol 7, pages 30-34.〕 In 1818 the French chemist and pharmacist Henri Braconnot (1780–1855) devised a simpler method of purifying gallic acid from galls; gallic acid was also studied by the French chemist Théophile-Jules Pelouze (1807–1867),〔J. Pelouze (1833) ("Mémoire sur le tannin et les acides gallique, pyrogallique, ellagique et métagallique," ) ''Annales de chimie et de physique'', vol. 54, pages 337-365 (February 17, 1834 ).〕 among others. George Washington used gallic acid to communicate with spies during the American Revolutionary War, according to the miniseries ''America: The Story of Us''. Gallic acid is a component of some pyrotechnic whistle mixtures. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「gallic acid」の詳細全文を読む スポンサード リンク
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