Thermal decomposition of ferrous oxalate dihydrate studied by direct current electrical conductivity measurements

The feasibility of the use of direct current electrical conductivity,, measurements in the study of solid-state reactions involved in the synthesis of-Fe₂O₃ from ferrous oxalate dihydrate has been reported. The study has been carried out in static air, dynamic air, dry nitrogen and dynamic air + water vapour environments. The conductivity data determined in static air are quite complex; nevertheless, the formation of Fe₃O₄ and-Fe₂O₃ with the probable intermediate formation of-Fe₂O₃ has been indicated. In dry nitrogen the step corresponding to dehydration is well resolved in the temperature region 145–220° C; the formation of FeO and Fe₃O₄ is also well characterized. In dry dynamic air the reaction further proceeds to the formation of-Fe₂O₃. In dynamic air containing water vapour there are definite indications of the formation of-Fe₂O₃ prior to the formation of-Fe₂O₃. Definite experimental conditions have been determined for the formation of-Fe₂O₃ in dynamic air containing water vapour. The conductivity measurements have been supplemented with infra-red spectroscopy and X-ray diffraction pattern measurements. The electrical conductivity measurements were found to give additional information on the solid-state reaction to that obtained from conventional thermal analytical techniques (such as differential thermal, thermogravimetric and differential thermogravimetric analyses).Fe₂O₃, obtained from the decomposition of FeC₂O₄ · 2H₂O in dynamic air + water was found to have a coercive force of 3.142 A m^–1, a saturation magnetization value of 7.1 T kg^–1 and a ratio of remanence to saturation magnetization of 0.64.