K6(CN)12Fe2

from The Collaborative International Dictionary of English v.0.48

Ferricyanide \Fer`ri*cy"a*nide\ (?; 104), n. [Ferri- + cyanide.]
   (Chem.)
   One of a complex series of double cyanides of ferric iron and
   some other base.
   [1913 Webster]

   {Potassium ferricyanide} (Chem.), red prussiate of potash; a
      dark, red, crystalline salt, {K6(CN)12Fe2}, consisting of
      the double cyanide of potassium and ferric iron. From it
      is derived the ferrous ferricyanate, Turnbull's blue.
      [1913 Webster]