THE PREPARATION OF TANNIC ACID. 87 
pared by these directions when dried at 120° gave the 
following percentage composition : 
52.10 per cent. 
C . 
H . 
O . 
3.52 “ 
44.38 “ 
100.00 “ 
An acetyl derivative was prepared of the same 
sample which melted at 139°, and by boiling with 
magnesium oxide according to the usual process gave 
very close to the theoretical quantity of magnesium 
pyrophosphate that would indicate pentacetyl-tannin. 
