SECTION IV. 
THE PROPERTIES OF TANNIC ACID. 
Tannic acid occurs in yellowish-white amorphous 
powder or masses which are easily pulverized; it is 
odorless, and possesses a strongly astringent taste, free 
from bitterness. By exposure to light it becomes yel¬ 
low to brown in color. 
It is soluble in 6 parts of water, in 6 parts of glycerin, 
and in 0.6 part of alcohol. The solutions are yellow 
in color, react acid with litmus, and are nearly without 
action on polarized light. Ether containing water or 
alcohol dissolves tannic acid, but absolute ether dis¬ 
solves it sparingly, while it is insoluble in chloroform, 
benzol, petroleum ether, carbon disulphide, fixed and 
volatile oils, except oil of bitter almond, which dis¬ 
solves it. 
A number of salts, as potassium acetate, ammonium 
chloride, calcium chloride, and sodium chloride, as well 
as the mineral acids, sulphuric, hydrochloric, arsenic, 
and boric acids, precipitate tannic acid from its concen¬ 
trated aqueous solution. Nitric acid does not so pre¬ 
cipitate it. When air and light are excluded from the 
aqueous solution of tannic acid, it remains for some 
time without decomposition, but in contact with air 
oxygen is absorbed, with the formation of a dark color 
and the production of sugar, gallic acid, and sometimes 
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