Potassium ferrioxalate

Potassium ferrioxalate, also known as potassium trisoxalatoferrate(III), is a chemical compound with the formula K₃[Fe(C₂O₄)₃], where iron is in the +3 oxidation state. It is an octahedral transition metal complex in which three bidentate oxalate ions are bound to an iron center. Potassium acts as a counterion, balancing the −3 charge of the complex. Crystals of the trihydrated form of the complex, K₃[Fe(C₂O₄)₃]·3H₂O, are emerald green in color. In solution, the salt ionizes to give the ferrioxalate anion, [Fe(C₂O₄)₃], which appears fluorescent green in color. Potassium ferrioxalate is often used in chemical actinometry, i.e. the measure of light flux.