The Collaborative International Dictionary of English v.0.48:

Ferricyanic \Fer`ri*cy*an"ic\, a. [Ferri- + cyanic.] (Chem.)
   Pertaining to, or derived from, a ferricyanide.
   [1913 Webster]

   Ferricyanic acid (Chem.), a brown crystalline substance,
      H6(CN)12Fe2, obtained from potassium ferricyanide, and
      regarded as the type of the ferricyanides; -- called also
      hydro-ferricyanic acid, hydrogen ferricyanide, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ferricyanic acid
    n 1: a brown unstable acid formed from ferricyanide