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[en] Reduction of Np(7), Pu(6), and Am(6) with metallic aluminium in alkaline solutions has been studied at different concentrations of NaOH and transuranium elements. Actinides have been reduced at room temperature by immersing an aluminium plate into a studied alkaline solution of Np(7), Pu(6), or Am(6) compounds upon intensive stirring of the solution. It has been shown that reduction of alkaline solutions of neptunium (7), plutonium (6), and americium (6) with metal aluminium gives, in accordance with redox potentials of the reagents, hydroxides of pentavalent neptunium, tetravalent plutonium and trivalent americium

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[en] An accurate determination of the formal redox potential (Esub(f)) of the Np(6)-Np(5) and Pu(6)-Pu(5) pairs in solutions of 2.5-4.0 M LiOH was carried out by the potentiometric method. The values of Esub(f) of the Np(6)-Np(5) and Pu(6)-Pu(5) pairs in 2.5 M LiOH were found to be equal to 0.150 and 0.2555 V, respectively. It was shown that the value of Esub(f) was practically independent on the alkali concentration in the region investigated

[en] The polarographic behaviour of tetravalent U, Np and Pu hexachloride complexes of composition (Et₄N)₂AnCl₆ in acetonitryl on mercury drop electrode has been studied. The reduction was found to involve two stages, first to the three-valent state, than to an amalgam. All the waves shown by the complexes are irreversible. On a rotating platinum microelectrode the complexes are polarographically inactive. It is shown that An(4) in acetonitryl forms strong complexes with chloride ions. Thus the potentials of the half-waves corresponding to the reduction into An(3) are very negative

[en] The polarographic behaviour of tetravalent uranium, neptunium and plutonium solvates (U(ClO₄)₄x9DMSO, Np(ClO₄)₄x8DMSO and Pu(ClO₄)₄x8DMSO) in dimethylsulfoxide on mercury drop electrode (m.d.e.) and rotating platinum electrode (r.p.e.) has been studied. All the three compounds undergo two-stage reduction, first to the three-valent state and then to an amalgam (on m.d.e.). On the r.p.e. there is one wave corresponding to the process An⁴⁺ + e → An³⁺. All the uranium reduction waves are irreversible. On the m.d.e. neptunium shows a reversible wave of reduction of Np⁴⁺ to Np³⁺. On the r.p.e. the waves of Np⁴⁺ and Pu⁴⁺ are almost reversible. Chloride-ions did not affect the reduction tetravalent U, Np and Pu. The potential shift of ion pairs U⁴⁺/U³⁺, Np⁴⁺/Np³⁺ and Pu⁴⁺/Pu³⁺ in DMSO as against water is explained in terms of pronounced solvation of tertravalent actinoid ions

[en] The problem of isotope effect in protium-tritium isotope exchange is considered. It is shown that for isotope exchange with water, large isotope effects should be observed for compounds with low frequency of R-H bond vibration. Isotope exchange in a water-bimaleate ion system containing such a bond was investigated with tritium. The water-bimaleate distribution coefficients thus obtained, α₂₉₈⁰K = 9.4 +/- 0.5, and α₃₇₃⁰K = 1.5 +/- 0.1, agree qualitatively with the calculated values

[en] The possibility has been studied of electrolytic preparation of neptunium (7) in aqueous alkaline solutions by neptunium oxidation on anodes from lead dioxide, graphite, nickel, stainless steel and iron. Optimum conditions have been found for neptunium (7) electrolytic preparation on the anodes under study in an alkaline medium. It has been shown that stability of the solutions of heptavalent neptunium obtained on these anodes is lower than that of neptunium obtained on a platinum anode