SOME ADVANTAGES OF CARBON PASTE ELECTRODES IN THE MORPHOLOGICAL-STUDY OF FINELY DIVIDED IRON-OXIDES

The electroreduction of finely divided trivalent iron oxides using a carbon paste electrode occurs according to a mechanism involving the dissolution of the solid and then the reduction of solvated Fe**3** plus ions into Fe**2** plus ions. The voltammetric curves exhibit two peaks. The first is due to the reduction of Fe**3** plus ions that come from dissolution of the smallest particles at the beginning of the experiment. The second is characteristic of reduction of the solid; its shape, position and amplitude are influenced by morphology. Theoretical aspects are considered. It appears that the use of a carbon paste electrode for the study of divided solids containing an electroreactive ion can easily give information either on the particle size distribution, if the dissolution kinetics of the compound are known, or on the dissolution kinetics of monodisperse solids or solids whose particle size distribution is well defined.