Ferrocyanic \Fer`ro*cy*an"ic\, a. [Ferro- + cyanic: cf. F. ferrocyanique.]

(Chem.) Pertaining to, derived from, or designating, a ferrocyanide.

ferrocyanic acid (Chem.), a white crystalline substance, H4(CN)6Fe, of strong acid properties, obtained from potassium ferrocyanide, and regarded as the type of the ferrocyanides; -- called also hydro-ferrocyanic acid, hydrogen ferrocyanide. etc.

Source: Webster's Revised Unabridged Dictionary (1913)