A tannin, usually in the form of a yellowish-white
or pale brown powder, obtained from fermented oak
galls by extraction with water-saturated ether.
Tannic acid is soluble in water, alcohol, and
acetone, and gives precipitates with most metallic
salts, proteins, and alkaloids. Chemically, it is
a penta-m-digalloyl-glucose having a high
molecular weight. Upon hydrolysis with sulfuric
acid, it gives gallic acid and glucose. See also:
VEGETABLE TANNINS .