Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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tannic acid

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 .




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