Photo: Korky Buchek via Wikimedia Commons under a Creative Commons 4.0 license.

Potassium trioxalatoferrate(III) contains the complex ion, [Fe(C2O4)3]3- in which three oxalate ions bind to an iron(III) ion in an octahedral arrangement.

The oxalate ions behave as ligands. Potassium trioxalatoferrate(III) can be prepared from ammonium iron(II) sulphate. A solution of the  latter is first treated with oxalic acid to form a precipitate of iron(II) oxalate and ammonium hydrogensulphate solution. The iron(Il) oxalate is isolated from the mixture and on reaction with hydrogen peroxide and potassium oxalate, potassium trioxalatoferrate(III) and a precipitate of iron(III) hydroxide are produced. On further treatment with oxalic acid, the iron(III) hydroxide reacts to form more potassium trioxalatoferrate(III)

Trioxalatoferrate synthesis – pupil guide

Trioxalatoferrate synthesis – Teacher’s guide

Trioxalatoferrate synthesis – Risk assessment