FeCO6

Iron hexacyanoferrate(II), commonly referred to as ferrous hexacyanoferrate or simply FeCO₆, is a coordination compound with the chemical formula K₄[Fe(CN)₆]·3H₂O when hydrated. It belongs to the broader class of hexacyanoferrates, which are coordination complexes containing the hexacyanoferrate ion, [Fe(CN)₆]⁴⁻. This compound is notable for its role in analytical chemistry and industrial applications.

The structure of FeCO₆ involves a central iron(II) ion coordinated by six cyanide ligands (CN⁻), forming an octahedral geometry. The hydrated form contains three water molecules per formula unit, contributing to its solubility in water. Ferrous hexacyanoferrate is often encountered as a precipitate in qualitative inorganic analysis, particularly in tests for potassium ions (K⁺). When potassium ions are present, they react with the hexacyanoferrate(II) ion to form a deep red precipitate of potassium ferrocyanide, which is a characteristic confirmation of potassium’s presence.

In industrial settings, hexacyanoferrates are used in wastewater treatment to remove heavy metals such as copper, zinc, and cadmium through precipitation. They also find applications in dyeing and electroplating processes. The compound is relatively stable under normal conditions but can decompose upon heating or in strongly acidic environments, releasing toxic cyanide gas.

Safety considerations are important due to the potential toxicity of cyanide-containing compounds. Proper handling, ventilation, and adherence to safety protocols are essential when working with ferrous hexacyanoferrate or related substances. Its properties and reactions make it a valuable reagent in both laboratory and industrial contexts.