C14H10O9

Tannic \Tan"nic\, a.
   Of or pertaining to tan; derived from, or resembling, tan;
   as, tannic acid.
   [1913 Webster]

   {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.
       [1913 Webster]