To a solution prepared from 2.8 g of cobalt sulfate heptahydrate in 30 mL of water, 1.6 g of sodium oxalate is added with stirring while the mixture is heated to 50°C for 5 minutes. The mixture is filtered, washed with water and the residue is dried in open air. The compound is obtained in a dihydrate form.
CoSO4 · 7H2O + Na2C2O4 = CoC2O4 · 2H2O + Na2SO4 + 5H2O
Preparation of the oxalate
The dried product