82 
THE TANNINS. 
«centage of tannic acid, are by the manufacturer pre¬ 
ferred to the Turkish variety. 
The galls are first crushed and then passed through 
a mill which will powder by cutting rather than by 
grinding, so as to furnish a moderately fine powder 
that is not “ balled” or “ caked.” 
A quantity of the powder is then stirred, in a wooden 
or copper vessel, with sufficient water to form a concen¬ 
trated aqueous solution, or this may better be accom¬ 
plished with a more complete exhaustion of the galls by 
a battery of vessels or extractors in which the liquors 
are run from one to another until of proper strength. 
The temperature of the water is recommended to be 
from 40° to 60°, although this varies with different 
manufacturers. When the liquors have reached the 
proper strength, they are run into a large settling-ves¬ 
sel and allowed to cool and settle for twelve hours; 
especially is this necessary if a higher temperature than 
that above mentioned has been used. From the set¬ 
tling-tub the liquor is run through a filter into a cylin¬ 
drical copper vessel like a churn, in which are numerous 
paddles so attached as to be capable of slow and contin¬ 
uous revolution. To the liquor in this vessel about 
one-fourth its volume of ether (specific gravity .750) 
is added. The mixture is then thoroughly agitated by 
means of paddles. The longer this operation is con¬ 
tinued the better the product is supposed to be, and 
when completed the emulsion-like liquid is run into a 
settling-vessel and allowed to stand for from eight to 
ten days, at the end of which time the complete separa¬ 
tion into two layers will be found to have taken place. 
The upper, ethereal layer, which holds in solution 
