*ferrocyanic*

a. [ Ferro- + cyanic: cf. F. ferrocyanique. ] (Chem.) Pertaining to, derived from, or designating, a ferrocyanide. [ 1913 Webster ]

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. [ 1913 Webster ]