What is a Potassium ferrocyanide?

Potassium ferrocyanide (chemical formula: K₄[Fe(CN)₆]·3H₂O) is a pale yellow crystalline compound that is soluble in water. It is a coordination complex containing a ferrous iron center (Fe²⁺) surrounded by six cyanide ligands, balanced by four potassium ions. Despite the presence of cyanide ligands, it is low in toxicity due to the strong bonding of cyanide to the iron atom. It is considered safe under normal handling and is even used as a food additive (E536) to prevent clumping in table salt and other products.

In analytical chemistry, it is known for its reaction with ferric ions (Fe³⁺) to form Prussian blue, a deep blue pigment used for detecting iron.

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