HISTORY. 
75 
sugar in the solution remaining after converting tannic 
into gallic acid, by treating this solution with acetate 
of lead, filtering, removing the lead from the filtrate by 
hydrogen sulphide, and applying potassium hydrate and 
copper sulphate, whereby he obtained the reduction to 
cuprous oxide. This he attributed to the presence of 
sugar or a related carbohydrate. He further investi¬ 
gated the elementary composition of tannic acid and 
arrived at the formula C 40 H 36 O 26 , and he explained the 
change into gallic acid and sugar as follows : 
QtoH 36 0 26 + 10H 2 O = 2C 14 H 16 0 12 t c 12 h 24 o 12 . 
These formulas were changed somewhat in his second 
paper, two years later, when he arrived at the follow¬ 
ing conclusions : 
“ Tannic acid is a glucoside, and is split, through the 
action of acids, alkalies, or ferments, into gallic acid 
and glucose. 
u The formula for tannic acid is C 54 H 44 0 34 , in which 
three equivalents of water are replaced by metallic 
oxides. The precipitate obtained by acting on tannic 
acid solution with acetate of lead consists in great part 
of a basic salt in which are contained ten equivalents 
of lead oxide to one equivalent of tannic acid. 
“The hitherto accepted compounds of tannic acid 
with hydrochloric and sulphuric acids do not exist. 
“ Gallic acid, C 14 H 12 O 10 , is, as tannic acid, a dibasic 
acid. 
“Other tannins are likewise glucosides, and contain 
apparently also thirty-four equivalents of oxygen.” 
The tannic acid used in these experiments was pre¬ 
pared by Pelouze’s method, and purified in one case bv 
