Ferricyanide is the anion [Fe(CN)₆]³⁻.  It is also called hexacyanoferrate(III) and in rare, but systematic nomenclature

Systematic name

A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection...

, hexacyanidoferrate(III). The most common salt of this anion is potassium ferricyanide

Potassium ferricyanide

Potassium ferricyanide is the chemical compound with the formula K3[Fe6]. This bright red salt contains the octahedrally coordinated [Fe6]3− ion. It is soluble in water and its solution shows some green-yellow fluorescence.-Preparation:...

, a red crystalline material that is used as an oxidant in organic chemistry

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

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Properties

[Fe(CN)₆]³⁻ consists of a Fe³⁺ center bound in octahedral geometry to six cyanide

Cyanide

A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

 ligand

Ligand

In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

s. The complex has O_h symmetry

Symmetry group

The symmetry group of an object is the group of all isometries under which it is invariant with composition as the operation...

. The iron is low spin and easily reduced to the related ferrocyanide

Ferrocyanide

Ferrocyanide is the name of the anion Fe64−. In aqueous solutions, this coordination complex is relatively unreactive. It is usually available as the salt potassium ferrocyanide, which has the formula K4Fe6....

 ion [Fe(CN)₆]⁴⁻, which is a ferrous (Fe²⁺) derivative. This redox couple is reversible and entails no making or breaking of Fe-C bonds:

[Fe(CN)₆]³⁻ + e⁻ → [Fe(CN)₆]⁴⁻

This redox couple is a standard in electrochemistry

Electrochemistry

Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor , and which involve electron transfer between the electrode and the electrolyte or species in solution.If a chemical reaction is...

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Compared to normal cyanide

Cyanide

A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

s like potassium cyanide

Potassium cyanide

Potassium cyanide is an inorganic compound with the formula KCN. This colorless crystalline compound, similar in appearance to sugar, is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewelry for chemical gilding and...

, ferricyanides are much less toxic because of the tight hold of the CN^- to the Fe³⁺. They do react with mineral acids, however, to release highly toxic hydrogen cyanide gas.

Uses

Treatment of ferricyanide with ferrous salts affords the brilliant, long-lasting pigment Prussian blue

Prussian blue

Prussian blue is a dark blue pigment with the idealized formula Fe718. Another name for the color Prussian blue is Berlin blue or, in painting, Parisian blue. Turnbull's blue is the same substance but is made from different reagents....

, the traditional color of blueprints.