Formerly ferrid-, used in Organic Chemistry in the names of certain compounds to indicate the presence of iron in the ‘ferric’ state (cf. FERRO-, the corresponding prefix used when the iron is in the ‘ferrous’ state). Ferricyanhydric or Ferricyanic acid, an acid, H4FeCy6, procured from various ferricyanides, and crystallizing in lustrous brownish-green needles. Ferricyanide, a salt of ferricyanhydric acid, e.g., potassium ferricyanide, red prussiate of potash; ferrous ferricyanide, Turnbull’s blue. Ferricyanogen, the hypothetical radical FeCy2 supposed to exist in ferricyanhydric acid.
1845. G. E. Day, trans. Simon’s Anim. Chem., I. 16. It [albumen] is precipitated from its solution in these acids by ferrocyanide and ferridcyanide of potassium, the former of which yields a white, and the latter a yellow, precipitate.
1848. Craig, Ferridcyanogen.
1854. J. Scoffern, in Orr’s Circ. Sc., Chem. 443. A … hydracid, ferrosesquicyanic acid, or ferridcyanic acid.
1869. Roscoe, Elem. Chem., 377. Ferricyanic Acid, H3FeCy6, forms a reddish-brown acid liquid.
1878. Kingzett, Anim. Chem., 379. Albuminoid solutions containing acid give with potassic ferro- and ferri-cyanide, precipitates not furnished by ordinary aqueous solutions.
