ferricyanide

n.
Any of various salts containing the negative trivalent radical Fe(CN)₆ and used in making blue pigments.

The common name for hexacyanoferrate(III), a compound containing the complex ion [Fe(CN)₆]³⁻.

The [Fe(CN)₆]³⁻ ion is kinetically unstable, and it dissociates to give the free cyanide anion, CN⁻. It is therefore quite toxic. In contrast, the ferrocyanide ion, [Fe(CN)₆]⁴⁻, is stable.

The sodium [Na₃Fe(CN)₆] and potassium [K₃Fe(CN)₆] salts have been isolated as ruby-red crystals and are photosensitive. The potassium salt reacts with metallic silver to produce silver ferrocyanide, and it is used in photographic processes. In addition, the [Fe(CN)₆]³⁻ ion is used in blueprint materials, wood stains, and electroplating process, and as a mild oxidizing agent in organic synthesis.

The addition of Fe II to ferricyanide produces Prussian blue (Fe₄ III) [Fe II (CN)₆]₃ · xH₂O, where x = ∼14–16), a pigment discovered nearly 300 years ago. The structure of this mixed-valence complex has been determined by x-ray analysis and powder neutron diffraction studies. See also Coordination chemistry; Coordination complexes; Cyanide; Iron.

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The noun has one meaning:

Meaning #1: salt of ferricyanic acid obtained by oxidation of a ferrocyanide

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