K4Fe(CN)6 - Potassium Ferrocyanide

What is Potassium Ferrocyanide?

Potassium ferrocyanide is an inorganic compound with the chemical formula K4Fe(CN)6. Potassium ferrocyanide is also known as yellow potash prussiate, a yellow crystal. It was made with wool or horn clippings stirring hot potassium carbonate with an iron rod. Potassium ferrocyanide was used for certain iron processes as a developer and as an additive for developers of alkaline pyro.

Other names – yellow prussiate of potash, potassium hexacyanoferrate (II)


Potassium ferrocyanide


1.85 g/cm³

Molecular Weight/ Molar Mass

368.35 g/mol

Boiling Point

400 °C

Melting Point

300 °C

Chemical Formula


Potassium Ferrocyanide Structure – K4Fe(CN)6

Potassium Ferrocyanide Structure

Physical Properties of Potassium Ferrocyanide – K4Fe(CN)6


No odour


Light yellow, crystalline granules

Covalently-Bonded Unit


Hydrogen Bond Acceptor





Insoluble in ethanol, ether

Chemical Properties of Potassium Ferrocyanide – K4Fe(CN)6

  • Potassium ferrocyanide reacts with sulfuric acid in aqueous medium forms potassium sulfate, ferrous sulfate, ammonium sulfate and carbon monoxide.
  • K4[Fe(CN)6] + 6H2SO4 + 6H2O → 2K2SO4 + FeSO4 + 3(NH4)2SO4 + 6CO

  • Potassium ferrocyanide reacts with ferric chloride forms a complex compound Iron (III) potassium hexacyanidoferrate(II) and potassium chloride.
  • K4[Fe(CN)6] + FeCl3 → KFe[Fe(CN)6] + 3 KCl

Uses of Potassium Ferrocyanide – K4Fe(CN)6

  • Used in the tempering of steel and in process engraving. It is employed in the manufacture of pigments and as a chemical reagent.
  • A small amount in pyro and hydroquinone developers tends to lower fog and give greater density.
  • Used in the manufacture of potassium cyanide, which is used extensively in gold mining.
  • Ferro Cyanogen forms with most metal compounds insoluble in water some of which exhibit highly characteristic colors. It serves as a test for cupric and ferric compounds.

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