THE PREPARATION OF TANNIC ACID. 83 
resin, fat, coloring-matter, gallic and ellagic acids, is 
drawn off and the ether recovered by distillation. The 
lower layer, consisting of water, ether, tannic acid, and 
some impurities, is also run into a still and a portion 
of the ether recovered by distillation until the liquid 
reaches a syrupy consistence. After cooling, this liquid, 
which still contains some ether, is spread by means of 
a brush on plates of sheet tin, and the tin plates are 
placed for a moment on the hot steam-coil, or flat iron 
surface heated with steam, and over the whole is placed 
a wooden box. The tannic acid almost immediately 
“ puffs up” and dries, although this spongy condition 
is said to be materially assisted by passing over the acid 
a jet of dry steam, which softens it slightly and admits 
of its swelling still further. Considerable practice and 
dexterity are required in this operation, which exposes 
the operator to the vapor of ether unless great precau¬ 
tions are taken. Excellent results have also been gotten 
by spreading the solution on plates of glass and placing 
them in a drying-oven heated to 110°, which may be 
so ventilated as to protect the operator. 
The product is the ether-tannin, and should be nearly 
white and completely soluble in water and in alcohol. 
The needle or so-called “ crystal-tannin” is prepared 
as above, but, instead of spreading the solution on tin 
or glass, it is run through small holes and allowed to 
fall in a very thin stream on a revolving hot cylinder 
of copper, from which the dried product is scraped in 
the needle form, which gives the impression of its being 
crystallized. 
Alcohol-tannin is prepared by extracting the galls 
with diluted alcohol (50 per cent.) instead of water, care- 
