What does ferrocyanide mean?
Ferrocyanide is the chemical term for the complex anion [Fe(CN)₆]⁴⁻, in which a single iron atom in its +2 oxidation state is surrounded by six cyanide groups, as well as for any salt containing that anion. Its best-known compound, potassium ferrocyanide, appears in everyday life as the anticaking agent in ordinary table salt and in industry in processes such as blue pigment production and wine making. Despite its alarming name, ferrocyanide binds its cyanide groups so tightly that it is far less dangerous than simple cyanides, though strong acids can break it down to release poisonous hydrogen cyanide. Chemists distinguish it from ferricyanide, which differs only in the oxidation state of its iron atom. The word derives from the Latin ferrum, meaning iron, joined to cyanide. It remains a staple of analytical chemistry, electrochemistry, and laboratory teaching.
nounA divalent anion consisting of iron in its +2 oxidation state coordinated to six cyanide groups, Fe(CN)₆⁴⁻; also any salt containing this anion, such as potassium ferrocyanide.
- The complex anion [Fe(CN)₆]⁴⁻, in which an iron(II) centre is bound to six cyanide ligands.
- Any of various salts containing this anion, such as potassium ferrocyanide or sodium ferrocyanide.
"The lab technician added a drop of the reagent, and the faint blue precipitate confirmed the presence of ferrocyanide in solution."
"Potassium ferrocyanide is added to table salt in tiny amounts to keep the crystals from clumping."
"In acidic conditions, ferrocyanide can decompose and release highly toxic hydrogen cyanide gas."
Pluralized when referring collectively to different salts of the ferrocyanide anion.
"Alkali ferrocyanides are generally stable crystalline solids."
Despite carrying 'cyanide' in its name, ferrocyanide is so tightly bound to its iron atom that one of its salts is even sprinkled into table salt as a safe anticaking agent.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of ferrocyanide
Ferrocyanide combines the combining form ferro-, from the Latin ferrum meaning 'iron', with cyanide, which traces back through French to the Greek kyanos, meaning dark blue. The name was coined in the early days of modern chemistry to describe iron-containing cyanide complexes, reflecting both their composition and their association with deep-blue pigments such as Prussian blue, which is formed from ferrocyanide and iron ions. The same roots give chemists the parallel terms ferrous, ferric, and ferricyanide.
How ferrocyanide is actually used
A technical term confined chiefly to chemistry and industrial contexts. Although the '-cyanide' suffix suggests extreme toxicity, ferrocyanide compounds are notably more stable and less acutely toxic than simple cyanides because the cyanide groups are strongly bound to the iron centre; they can nevertheless release toxic hydrogen cyanide under strongly acidic conditions.
Easily confused with ferrocyanide
Ferricyanide contains iron in the +3 oxidation state, Fe(CN)₆³⁻, whereas ferrocyanide contains iron in the +2 state, Fe(CN)₆⁴⁻.