HISTORY. 71 
I. 
II. 
c. 
. 51.30 
51.36 
H. 
. 3.83 
3.76 
0. 
44.88 
100.00 
100.00 
These results he shortly after sent in a letter to Liebig, 
in which he stated that, while the difference was very 
slight, he was inclined to accept the latter’s formula 
of C 18 H 16 0 12 , in which view Dumas concurred. With 
some unimportant reservations Berzelius, in his Jahres- 
bericht, 1840, accepted this formula also. 
In 1836, Leconnet suggested another method for pre¬ 
paring tannin, by stirring finely-powdered galls with 
sufficient ether to make a thin mixture, and allowing 
to stand twenty-four hours. The mass was then pressed 
between strong linen, this process was repeated with 
more ether, and the syrupy liquid evaporated. He 
claimed a larger yield (40 to 60 per cent.) than that 
obtained by Pelouze, with the use of much less ether. 
Robiquet about this time directed his attention to the 
decomposition of tannin with the formation of gallic 
acid. Contrary to the observations of Pelouze, he 
found that the change to gallic acid would take place 
without access of air or oxygen, but found it was caused 
by a ferment in the galls. These observations were 
confirmed by Larocque in 1841. 
Previous to the investigations of Stenhouse in 1842, 
such authorities as Pelouze, Berzelius, and Liebig con¬ 
sidered the tannins from all sources to be identical, 
differing only in purity. Although Proust had stated 
forty years before that there probably existed “ several 
different species of the tanning principle,” Stenhouse 
