The Elements of Materia Medica and Therapeutics Volume 2, PT. 1 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1855 Excerpt: ... nitrogenous matter, of the same nature as ordinary ferment, contained in the crude gall nut. The conversion to gallic acid is prevented by all those substances which destroy the fermenting properties of yeast. It has been hitherto considered that the access of oxygen is necessary to this change; but, according to Regnault, oxygen or air is not 1 Pelouze, Ann. de Chim. et de Physique, t. liv. PharmaceuticalJoumal, June 1853, p. 597.--Ed. VOL. II. 2 A required; and in this respect the gallic resembles the alcoholic fermentation. Regnault states that gallic acid is a result of the decomposition of an extract of galls even in a vessel hermetically sealed. It is not improbable, therefore, that the production of gallic acid may be in some cases increased by the addition of ordinary ferment (yeast), as it is often procured with difficulty and only in small quantity from common galls.--Ed. The following are the characteristics of this substance: --It has an intensely astringent taste, and a slightly acid reaction. It produces with a solution of gelatin a white precipitate (tannate of gelatiti); with a solution of a sesquisalt of iron, a deep blue compound (tannate of iron); and with solutions of the vegetable alkalies, white precipitates (tannates), slightly soluble in water, but very soluble in acetic acid. The mineral acids also cause precipitates with concentrated solutions of tannic acid, as do the alkalies and their carbonates. The carbonates are decomposed by a strong solution of it. The diluted sulphuric or hydrochloric acid, on boiling, converts it to gallic acid.--Ed. Gelatinous alumina rapidly absorbs tannic acid from its solution, and forms an insoluble compound with it. When a few drops of a solution of this acid are added to a glass of lime-water, a d..