High Quality Content by WIKIPEDIA articles! Sodium ferrioxalate, also known as sodium oxalatoferrate, is a chemical compound with the formula Na3, where iron is in the +3 oxidation state. It is an octahedral transition metal complex in which three bidentate oxalate ions act as ligands bound to an iron centre. Sodium acts as a counterion, balancing the -3 charge of the complex. Crystals of the hydrated form of the complex, Na3.xH2O, are lime green in colour. In solution the complex dissociates to give the ferrioxalate anion, 3-, which appears a deep apple green in colour.