SECTION v. 
THE COMPOSITION AND CONSTITUTION OF TANNIC 
ACID. 
As stated in the history, numerous investigators in 
the first half of this century made efforts to establish 
the composition of tannic acid. Mulder actually de¬ 
termined the formula, C 14 H 10 O 9 , accepted at the present 
time. It was not, however, until Lowe in 1867 pre¬ 
pared digallic acid by treating barium gallate with sil¬ 
ver nitrate, and Schiff in 1871 studied the conversion 
of gallic into tannic acid by means of phosphorus 
oxychloride, that the foundation of our present knowl¬ 
edge was laid. 
No better idea can be given of the importance of 
Schiff’s work than by quoting portions of his papers. 
He first called attention to the fact that some chemists 
held the view that tannic acid was a glucoside, while 
others considered glucose to be an admixture, which 
varied much in its proportion, and that the behavior of 
the acid towards reagents was not altered by the removal 
of the glucose. SchifFs method of forming digallic 
acid was as follows : 
“When well-purified gallic acid dried at 110° is 
mixed with phosphorus oxychloride to the consistence 
of an emulsion and heated in a water-bath at 100° and 
afterwards in an oil-bath to 120°, there follows an abun- 
94 
