a. Chem. [f. TANN-IN + -IC.]. In tannic acid, a name introduced in 1834 by Pelouze instead of TANNIN, in recognition of its acid character and reactions; originally applied to the tannin principle obtained from oak-galls, a white amorphous strongly astringent substance, C14H10O9, now more particularly distinguished from other forms of tannin as GALLOTANNIC acid. Now chiefly used in a general sense to include a great number of allied substances, which differ in the proportion of their elements.
These are distinguished by compound names indicating their source, as quercitannic acid, that obtained from oak-bark, C13H12O9; also caffetannic (C15H18O8), catechutannic (C17H17O9) cincho- or quinotannic (C14H15O3), fraxitannic, kinotannic, ratanhiatannic acids, obtained from coffee, catechu, cinchona, ash-leaves, kino, and ratanhia, respectively.
[1834. (Feb. 17) Pelouze, in Ann. de Chimie, LIV. 337. La place du tannin, qu’il serait plus convenable d’appeler acide tannique, est marqué à côté de l’acide gallique lui-même.]
1836. Brande, Chem. (ed. 4), 925. A peculiar proximate principle, designated tannin.… It has been obtained in a distinct form by Pelouze, and its characters are such that it may be appropriately termed tannic acid.
1869. Roscoe, Elem. Chem. (1871), 405. Tannin, or Tannic Acid,… is contained widely diffused in certain parts of plants.
1874. Garrod & Baxter, Mat. Med. (1880), 281. The cincho-tannic and red cinchonic acids are powerfully astringent—like tannic and gallic acids.
