918.] believed to have isolated a pentethylester of the pentagalloyl
glucoside from tannin, but this was shown to be the ethyl ester of
gallic acid.

Feist [Footnote: _Ber._, 1912, 45, 1493.] had arrived at the conclusion
that tannin was a glucose compound, and maintained that tannin from
Turkish galls was a compound of glucogallic acid combined as an ester
with 2 molecules gallic acid. But Fischer and Strauss [Footnote:
_Ibid._, 1912, 45, 3773.] synthetically prepared a glucoside of gallic
acid exhibiting differences from Feist's preparation which were so great
that the latter no longer could be considered a single glucoside of
gallic acid.

Fischer and Freudenberg [Footnote: _Ibid._, 1912, 45, 2717; 1913, 46,
1127.] subsequently elaborated a method of purifying tannin, and on
investigating the purified substance, arrived at the conclusion that
no other hydroxybenzoic acid than gallic acid was present in
tannin. On repeating Strecker's hydrolysis they obtained 7-8 per cent,
sugar, and hence concluded that 1 molecule of glucose was combined
with about 10 molecules of gallic acid. Owing to the difficulty of
isolating the intermediary hydrolysis products, and the subsequent
impossibility of drawing any conclusions as to the constitution of
tannin, the latter investigators decided to adopt the methods offered
by synthesis. Their basic idea was the absence of carboxylic groups in
tannin, and that hence the total gallic acid must be present in ester
form. These conditions are fulfilled if one views tannin as being an
ester compound of 1 molecule of glucose and 5 molecules of digallic
acid, of similar construction as, for example, pentacetyl
glucose. Fischer and Freudenberg succeeded in preparing the former by
shaking a mixture of finely powdered glucose, chloroform, and