THERMODYNAMIC PARAMETERS OF THE ME(4-BAR-REVERSIBLE-ARROW-ME(3+) REACTION (ME=AM AND CE) IN SOLUTIONS OF POTASSIUM PHOSPHOTUNGSTATE IN WATER AND AQUEOUS ACETONITRILE()+(E)OVER)

The oxidation potentials E(0)(p) of the reversible Me(IV)/Me(III) coup le (Me = Am and Ce) in solutions of potassium phosphotungstate (PT) in water and aqueous acetonitrile were measured by the potentiometric me thod in wide ranges of pH (0-7.7) and temperature (25-42 degrees C). T he shift of the oxidation potential of Am and Ce to the negative range as compared with the standard values is 1.25 V. Thermodynamic paramet ers (Delta G(298), Delta H, and Delta S) of the reaction Me(4+) + (e) over bar reversible arrow Me(3+) are calculated. The contribution of t he energy component to the change of the Gibbs free energy of the elec trochemical reaction is significantly higher than that of the structur al component. Thermodynamic parameters of the similar reaction for ber kelium in PT solutions are evaluated.