[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

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[en] The dependence is studied of the equilibrium constant Ke of the reaction of disproportionation of neptunium (6), on the alkali concentration, the initial concentration of neptunium (6), and the temperature. The dependence of Ksuh(e) on the alkali concentration is expressed in analytical form by the equation Ksub(e)=Ksub(0e)supαC), where C is the alkali concentration. K₀ and α are equal to 3.55x10^-5 and 0.553, respectively, at a temperature of 60 deg C. The initial concentration of Np(6) and the temperature in the range of 45-75 deg C do not affect the value of Ksub(e)

[en] Formal redox potential for the Np(7)-Np(6) couple in 1.-0.3M solutions of LiOH at constant ionic strength, μ (μ=1), was determined by the potentiometric method. In 1M LiOH the formal redox potential of the Np(7)-Np(6) couple is 0.604 V, and it grows when the concentration of LiOH decreases as in the case of NaOH. Polarographic curves for reduction of Np(7) into Np(6) and Np(5), and of Np(6) into Np(5) were registered using a rotating platinum electrode in 4-0.5M LiOH. The limiting current strength for reduction of Np(7) into Np(6) and of Np(7) into Np(5) are equal in height in 4-2M LiOH. In 2-0.5M LiOH a decrease of the height of the second wave of reduction of Np(7) into Np(5) is observed. This wave practically disappears at [LiOH] < 0.5M. The polarographic wave for reduction of Np(6) into Np(5) coincides in shape ahd height with the second wave of reduction of Np(7)

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[en] Atomic absorption spectrometry was used to determine zirconium (hafnium) in organic extracts based on acidic and neutral organic phosphorus compounds. The sensitivities achieved (3-9 μg/ml per 1% of absorption) were much lower than the values reported earlier for both organic extracts and aqueous solutions

[en] A mechanism is suggested which accounts for the influence of zirconium and some other elements on atomic absorption determination of hafnium. The possibility has been shown of eliminating the effects of the elements studied by addition of ammounium fluoride to the test solution. Conditions have been found for maximum hafnium atomization. Conditions have been chosen for determination of hafnium in the presence of zirconium with a sensitivity of 5.9 μg/ml (1% absorption)

[en] This paper studies the nature of the effect of various factors on the atomic absorption determination of zirconium and hafnium in organic solutions and the selection of the optimum conditions for conducting an analysis. Saturated hydrocarbons in the methane series (pentane, hexane, heptane, octane, decane, and dodecane) were used with the saturated alcohols C₂H₅OH, C₃H₇OH, C₄H₉OH, C₅H₁₄OH, C₇H₁₅OH. The other solvent were CCL₄, benzene, toluene, and trioctylamine. All the substances were of analytically pure grade. It is shown that the use of propanol or butanol as solvent, as well as measuring of atomic absorption of zirconium and hafnium at a flowrate of 240 liter/h of acetylene and 340 liter/h of nitrogen (I) oxide enables the sensitivity of the method to be raised to 3.5 and 7.5 ug/ml for 1% absorption for zirconium and hafnium respectively. Conducting an analysis under the conditions found enabled the destabilization of the flame to be avoided

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