O || HO ^ _ __C | | | | | }O | | | __OH | |____|_C_/ \OH HO V \__/ OH OH OH Dekker [Footnote: _Ber._, 1906, 34, 2497.] was enabled to account for most of the details in the behaviour of tannin, viz.: (1) the empirical constitution, C_14H_10O_9; (2) the almost complete hydrolysis into gallic acid (the dotted line indicates the decomposition of the molecule into 2 molecules gallic acid by taking up water); (3) the formation of diphenylmethane as a result of distillation with zinc dust; and (4) the electrical non-conductivity. Since tannin on acetylating yields a considerable amount of triacetylgallic acid, it should, according to Dekker, contain at least six acetylisable hydroxyls. Nierenstein [Footnote: _Chem. Ztg._, 1906, 31, 880.] objected to this formula on account of its containing seven hydroxyl groups, whereas Dekker found six, Nierenstein five, and Herzig still fewer hydroxyl groups. The formula would also favour the conception of tinctorial properties which could hardly be ascribed to tannin. Lloyd [Footnote: _Chemical News_, 1908, 97, 133.] proposed a very intricate formula containing three digallic acid groups joined into one six-ring system, which would then explain the optical activity; it would, on the other hand, also require an inactive cis-form. Iljin [Footnote: _Jour. of the Russian phys. chem. Soc._, 1908, 39, 470.] prepared two phenylhydrazine derivatives of tannin (C_74 H_58 N_8 O_30 and C_98 H_82 N_14 O_96) and proposed the formula, C_58 H_40 O_33, the constitution of which would be-- R_1 R_1 | | }C--O--O--C{ | | | R_2 | R_2 O R_1 | R_1 | | | }C--O--O--C{ | | R_2 R_2 where R1= CO C_6 H_2 (OH)_3 and R2= C_6 H_2 (OH)_2 Nierenstein [Footnote: _Ber._, 1905, 38, 3841; 1907, 40, 917; 1908, 41, 77 and 3015; 1909, 42, 1122 and 3552; _Chem. Ztg._, 1907, 31, 72; 1909, 34, 15.] considers tannin to be a mixture of digallic acid and leucotannin, the latter possessing the formula-- ^-------CH.OH--O----^ OH | | | | HO V OH HOOC V OH OH The optical activity of tannin is expressed in this formula and its probability is corroborated by Nierenstein, who was able to resolve the acetylated tannin by fractional precipitation into pentacetyl tannin (M.P. 203°-208° C.) and pentacetyl leucotannin (M.P. 166° C.). By oxidation, the former is converted into ellagic acid, and on hydrolysis with dilute sulphuric acid readily yielded gallic acid. Hydrolysis of the pentacetyl leucotannin, however, yielded gallic aldehyde, and oxidation yielded purpurotannin (a naphthalene derivative) in addition to ellagic acid.