Bottinger [Foonote: _Ber._, 1884, 1503.] made the first attempt at synthesising tannin; he heated gallic acid or its ethyl ester with glyoxylic acid or pyroracemic acid, and obtained a substance of the composition C_14H_10O_9.2H_2O, which certainly showed some of the characteristics exhibited by tannin, but which by no means was identical with the latter. Bottinger's preparation is probably identical with [Greek: b]-digallic acid, one of two dibasic isomers having the composition-- C_6H_2(OH)_2COOH | C_6H(OH)_3COOH the other possible isomer having the composition C_6H(OH)_3COOH CO | C_6H_2(OH)_3 Fischer [Footnote: _Ber_., 1908, 41, 2875.] obtained a digallic acid (M.P. 275°-280° C) by coupling tricarbomethoxygalloyl chloride with dicarbomethoxygallic acid. Nierenstein [Footnote: _Ibid_., 1910, 43, 628.] obtained, from the carbethoxy compound of tannin, a crystalline, optically active digallic acid, M.P. 268°-270° C. The pentacetate of this substance, obtained by reduction and acetylisation, yielded hexacetylleucotannin. A pentamethyldigallic acid methyl ester of the composition ((O.CH_3)_3)C_6H_2----COO-----C_6H_2((OCH_3)_2)COO.CH_3 was obtained by Mauthner [Footnote: _Jour. f. prakt. Chem_., 1911, 84, 140.] from the chloride of trimethylgallic acid and the methyl ester of the acid from the glucoside of syringin; on saponification with caustic potash the former compound yielded trimethylgallic acid and syringic acid. Fischer [Footnote: _Ber_., 1913, 46, 1116.] synthesised the so-called _m_-digallic acid by coupling tricarbomethoxygalloyl chloride with carbonylgallic acid and subsequent splitting off of CO_2. The _m_-digallic acid appears as rather thick, colourless, microscopic needles containing about 16 per cent. water of crystallisation, M.P. 271° C. They are slightly soluble in cold, soluble in hot water, and very soluble in methyl and ethyl alcohols. Their aqueous solution gives dark blue coloration with ferric chloride, and precipitates gelatine and quinine. Fischer and his students [Footnote 5: _Ibid_., 1912, 45, 915, 2709; 1913, 46, 1116.] prepared quite a number of digallic acid derivatives, amongst which are the following:-- Pentamethyl-_m_-digallic acid methyl ester, C_20H_22O_9. Pentacetyl-_m_-digallic acid, C_24H_20O_14. Pentamethyl-_m_-digallic acid, C_19H_20O_9. Pentamethyl-_m_-digalloyl chloride, C_19H_19O_8Cl. Pentamethyl-_p_-digallic acid, C_19H_20O_9. Pentamethyl-_p_-digallic acid methyl ester, C_20H_22O_9.