Tannic acid. (Chem.) (a) An acid obtained from nutgalls as a yellow amorphous substance, C14H10O9, having an astringent taste, and forming with ferric salts a bluish-black compound, which is the basis of common ink. Called also tannin, and gallotannic acid. (b) By extension, any one of a series of astringent substances resembling tannin proper, widely diffused through the vegetable kingdom, as in oak bark, willow, catechu, tea, coffee, etc.

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OXFORD DICTIONARY

tannic, adj. of or produced from tan.

Idiom

tannic acid a complex natural organic compound of a yellowish colour used as a mordant and astringent.

Derivative

tannate n.

Etymology

F tannique (as TANNIN)

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