86 
THE TANNINS. 
stant stirring until the precipitate ceases to be granular, 
but is more milky in character, ceases to settle, and is 
pure white in color, distinct from the yellowish color 
caused by the first drops of the reagent. The filtrate 
at this point will be colorless. It is important that the 
solutions be as dilute as the above mentioned, or else 
the precipitate of lead tannate will not carry down the 
coloring-matter with it. After filtration the precipitate 
is washed with sufficient water to bring 1 the filtrate to 
the original volume. More washing than this is to be 
avoided, on account of the tendency of the precipitate 
to decompose. 
The colorless filtrate, which contains free acetic acid, 
is agitated with 75 cc. of pure acetic ether and the lat¬ 
ter separated; this agitation is to be repeated twice 
with the same volume of acetic ether; the three por¬ 
tions are mixed and the ether recovered by distillation 
under reduced pressure to dryness. A light, porous, 
white tannic acid is obtained amounting to 41 per cent, 
of the original quantity. It contains gallic acid and 
has a pungent acetous odor; the aqueous solution of a 
portion of it, after the removal of the tannic acid by 
lead oxyacetate, gives no reaction with Fehling’s solu¬ 
tion for glucose. The tannic acid is further purified by 
dissolving in water, agitating the solution with stronger 
ether to remove gallic acid, and distilling the aqueous 
solution to dryness under reduced pressure. This is 
once more dissolved in ether with a little water, and 
again brought rapidly to dryness under reduced press¬ 
ure. The result is a pure white product which gives 
no reactions for gallic acid or glucose. A sample pre- 
