SECTION III. 
THE PREPARATION AND PURIFICATION OF TANNIC 
ACID. 
The separation of tannic acid in a nearly pure state 
was first accomplished by Proust in 1798, by precipi¬ 
tating the infusion of galls with stannous chloride, 
separating the tin from the precipitate by hydrogen 
sulphide, and evaporating the filtrate to dryness. This 
method, with its variation by using lead acetate in 
place of the tin salt, has done good service. The same 
in a lesser degree may be said of the process proposed 
by Berzelius, which consisted in precipitating the tan¬ 
nic acid by sulphuric or hydrochloric acid, digesting 
the precipitate, of tannic acid with the acid used, with 
lead carbonate, filtering, and evaporating to dryness. 
The above methods are not available for producing the 
acid on a large scale; and that by precipitation with 
hydrochloric or sulphuric acid is applicable only to 
galls. 
The numerous processes for obtaining tannic acid 
from galls became practically valueless after Pelouze in 
1834 published his method for obtaining the acid Iiy 
percolating galls with ether. This method, which is 
the one usually quoted in the text-books, consists in 
percolating powdered galls with commercial ether 
containing alcohol and water. 
The details of the operation are to pack the powder 
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