[en] The standard electrode potentials determined in this work are affected by the accuracy of determining delta E₂ and delta E₃, since these energies of amalgamation were estimated by correlation with those of some 4f elements. The accuracy on the measured half-wave potential itself is 5 mV for all elements, Bk and Cm excepted. Finally, we note that these standard potentials are in good agreement with those calculated by correlating the variation in P(M) function for 4f and 5f series. (auth)

[en] The theoretical treatment of controlled-potential coulometric method in the presence of kinetic effects has been investigated in the case of amalgamation electrode reactions. It showed that kinetic studies of these reactions can be undertaken by this technique even for elements at tracer scale concentrations (Radiocoulometry) using radioactive tracer

[en] Tabulations were recently published on the enthalpy of sublimation for the 4f and 5f metals at 298.15K, ΔH/sub S/⁰(M), and the standard enthalpy of formation at 298.15K, ΔH/sub f/⁰ (M/sub aq/³⁺), for the tripositive aqueous metal ions for these two series. Values in this tabulation for the latter half of the 5f series were not obtained from experimental measurements, but from theoretical consideration and empirical correlations drawn from the trends in the 4f series. In the present work new experimental data were used for the 5f series to modify the empirical correlations, and tabulate new values for ΔH/sub f/⁰ (M/sub aq/³⁺) and ΔH/sub S/⁰(M) for the second half of the 5f series. In addition, values for ΔG/sub f/⁰ (M/sub aq/³⁺) [ΔG/sub f/⁰ = -3FE⁰ (M/sub aq/³⁺/M) = ΔH/sub f/⁰ - TΔS/sub f/⁰ for the reaction M + 3H/sub aq/⁺ M/sub aq/₃+ ⁺ 3/2 H₂] are given for the 5f series and the oxidation-reduction properties of the 5f elements are discussed. (U.S.)

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[en] This work determines the standard E⁰III-0 or E⁰II-0 electrode potentials for some transplutonium elements in aqueous solution, and to obtain information of the electrochemical properties of 5f elements. In addition the standard electrode potentials are essential for the determination of some thermodynamic functions such as the enthalpy of formation ΔHsub(f) (M³⁺). This function, combined with others, is used for correlation between 4f and 5f series, allowing predictions of some unknown data on the heavy actinides elements. In this work the radiopolarography technique is used to study Am, Cm, Bk, Cf, Es and Fm. This technique permits a radiochemical determination of the half-wave E 1/2 potential by studying the electrochemical behaviour of the aquo-ion at the dropping mercury cathode. (Auth.)

No abstract available

No abstract available

[en] The function P(M) defined by Nugent, Burnett and Morss (J. Chem. Therm.; 5:665 (1973)) has been reexamined utilizing new experimental data. This function now appears to be linear with Z for the actinide series. New values for ΔH⁰sub(s) and ΔH⁰sub(f) for each element of the actinide series (Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr) are derived. The entropy of formation ΔS⁰sub(f) of the M³⁺sub(aq) ions was estimated which allowed the determination of the free energy change ΔG⁰ and redox potential E⁰ for the couple M³⁺sub(aq)/M. The redox potentials for E⁰(M(X)/M) for all known redox states of the actinide series were estimated. (author)

[en] The radiopolarographic method has been used to study the amalgamation reaction of elements from Am to Fm. The performances brought to the technique enable one to carry out study of kinetics and mechanism of the electrode reaction. It has been shown that Am³⁺, Cm³⁺, Bk³⁺, Cf³⁺ and Es³⁺ are reduced according to a single M³⁺ → M⁰ step, whereas the amalgamation of fermium is controlled by Fm²⁺ → Fm⁰ step. The kinetics of electrode reaction were discussed and reversible half-wave potentials were determined. The standard electrode potential of M³⁺/M⁰ couple has been estimated for all investigated elements. (author)

[en] The experimental data obtained from radiopolarographic and radiocoulometric measurements on transplutonium elements Am, Cm, Bk, Cf, Es and Fm permitted to explore the oxidation-reduction behavior of these elements in aqueous media. Mechanisms and kinetics of the electrochemical reduction to the metallic state at a mercury cathode have been stated. Am, Cm, Bk, Cf and Es are amalgamated according to M³⁺ + 3e + Hg reversible M(Hg) mechanism whereas M²⁺ + 2e + Hg reversible M(Hg) mechanism is observed for Fm. The reduction processes are reversible for Cf, Es and Fm. The determination of reversible half-wave potential for Cf, Es and Fm permitted to estimate the formal E⁰M³⁺/M⁰ potentials which are unmeasurable by classical methods