Ferricyanide

Ferricyanide is the hexacyanoferrate(III) anion, [Fe(CN)₆]³⁻, with an iron(III) center coordinated octahedrally by six cyanide ligands.

Ferrocyanide: Ferrocyanide is the hexacyanoferrate(II) anion, [Fe(CN)₆]⁴⁻, with iron in the +2 oxidation state. A one-electron reduction converts ferricyanide into this closely related anion.
Potassium ferricyanide: Potassium ferricyanide is the water-soluble salt K₃[Fe(CN)₆]. This common laboratory salt supplies ferricyanide ions in aqueous reactions.
Coordination complex: A coordination complex consists of a central metal atom or ion bonded to surrounding ligands. Ferricyanide is a compact example with one metal center and six ligands.
Prussian blue: Prussian blue is a mixed-valence iron(III)–iron(II) cyanide coordination solid with an intense blue color. Ferricyanide is a discrete soluble ion, whereas Prussian blue is an extended solid network.
Hexacyanoferrate(III): Hexacyanoferrate(III) is the coordination-ion family built around an iron(III) center and six cyanide ligands. This formal name identifies ferricyanide by its metal oxidation state and ligand count.
Cyclic voltammetry: Cyclic voltammetry measures current while an electrode’s potential is swept forward and backward. Ferricyanide is a common redox probe for testing electrode surfaces and electrochemical systems.
Oxidation state: Oxidation state is the formal charge assigned to an atom under an electron-bookkeeping convention. Iron has oxidation state +3 in ferricyanide, distinguishing it from ferrocyanide.
Nitroprusside: Nitroprusside is the [Fe(CN)₅NO]²⁻ coordination anion, containing iron, cyanide, and a nitrosyl ligand. It is a related iron cyanide complex with one cyanide replaced by nitrosyl.
Outer-sphere electron transfer: Outer-sphere electron transfer moves electrons between redox centers without changing their ligand coordination shells. Ferricyanide often accepts electrons while retaining its six cyanide ligands.
Blue bottle experiment: The blue bottle experiment is a color-changing redox demonstration involving a dye, glucose, and oxygen. Ferricyanide can replace the dye as an electron acceptor in related color-changing demonstrations.

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Potassium ferrocyanideCompared with: Its +3 iron center distinguishes it from the +2 center in ferrocyanide.