The Collaborative International Dictionary of English v.0.48:

Styphnic \Styph"nic\, a. [Gr. (spurious) sty`fein to contract.]
   (Chem.)
   Pertaining to, or designating, a yellow crystalline
   astringent acid, (NO2)3.C6H.(OH)2, obtained by the action
   of nitric acid on resorcin. Styphnic acid resembles picric
   acid, but is not bitter. It acts like a strong dibasic acid,
   having a series of well defined salts.
   [1913 Webster]