80 
THE TANNINS. 
(specific gravity 0.740), four parts water, and one part 
alcohol (90 per cent.) also make a good solvent. 
Equally good is the United States Pharmacopoeia ether 
(specific gravity 0.750), which is composed of seventy- 
four parts ether and twenty-six parts alcohol with a 
little water. Equal volumes of ether and alcohol have 
been recommended on account of the increased yield 
obtained; the product, however, is not so pure as that 
from a more ethereal solvent. 
In 1836, Leconuet proposed a method for extracting 
tannic acid by mixing the powdered galls with suffi¬ 
cient ether to make a paste, allowing the mixture to 
macerate, then expressing through muslin, and repeat¬ 
ing the process with more ether. The yield was found 
to be 60 per cent., and a comparatively small quantity 
of ether was employed. 
The process as modified by Domine in 1844 was 
adopted by the British and United States Pharmaco¬ 
poeias. This modification consisted in first exposing 
the powdered galls in a damp cellar for several days, 
to allow the absorption of moisture, and then macer¬ 
ating with commercial ether and expressing as in Lecon- 
net’s process. 
It has further been suggested to extract galls in such 
a manner as to form three layers of the percolate. To 
accomplish this, 10 parts of coarsely-powdered galls 
are placed in a percolator and a mixture of 12 parts 
stronger ether and 3 parts alcohol poured on, and the 
mixture allowed to stand two days, when the percola¬ 
tion is commenced and continued with the same mix¬ 
ture of ether and alcohol until 10 parts are obtained. 
The resulting percolate is mixed with one-third its 
