Synthesis of different polymorphic modifications of calcium oxalate by electrodeposition

Different hydrates of calcium oxalate have been electrodeposited by electrogeneration of acid at the anode from an EDTA-stabilized calcium nitrate bath containing dissolved oxalate ions. The deposition is controlled by varying the bath pH, temperature, and current density. Formation of metastable CaC₂O₄·2H₂O is favored at high current densities at ambient temperature, whereas the thermodynamically stable CaC₂O₄·H₂O is formed at elevated bath temperatures. Both the polymorphs show oriented growth with respect to the substrate normal under different deposition conditions.