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281.
282.
A new Am(V) chromate complex with outer-sphere cesium cation, Cs3AmO2(Cr2O7)2·H2O, was prepared from aqueous solution. Its composition and structure were determined by single crystal X-ray diffraction. The Am(V) atom has coordination surrounding in the form of a distorted pentagonal bipyramid with the O atoms of the AmO 2 + group in apical positions. The equator of the bipyramid is formed by the O atoms of four dichromate groups and of the water molecule. The mean bond lengths (Å) are as follows: Am=O 1.802(5), Am-O(Cr2O7) 2.443(6), and Am-Ow 2.519(6). The Am(V) pentagonal bipyramids are combined via bidentate bridging Cr2O 7 2? anions into infinite chains [AmO2(Cr2O7)2H2O] n 3? arranged in layers parallel to the series of diagonal planes (111). A system of hydrogen bonds links the chains in a layer and the layers with each other. The Cs cations are arranged between the layers, forming cationic interlayers. 相似文献
283.
The reaction of Np(VI) with organic acid anions in solutions containing lithium salts of tartaric, malic, α-aminoglutaric, and trihydroxyglutaric acids was studied. Changes in the solution spectra show that Np(VI) forms complexes with organic acid anions, which is followed by the reduction of Np(VI) to Np(V). Similar processes occur in solutions containing Pu(VI) and sodium phenylglycolate or ammonium salicylate. In weakly acidic solutions, the loss of the Np(VI) and Pu(VI) concentrations is a linear function of time. The possible mechanism of the redox reactions was suggested. 相似文献
284.
The theory of thermal processes, developed by N.N. Rykalin, is used for calculating the cooling rate, the temperature in heating and the width of quenched grooves in surface quenching with the electric arc. The results confirm that high-quality surface quenching of the components can be carried out without additional cooling of the surface with water. 相似文献
285.
The formal potential of the couple of nonoxygenated U5+/U4+ ions bound in complexes with unsaturated heteropoly anions (HPAs) P2W17O6110− (I) and SiW11
O398− (II) in 0–1 M NaNO3 and 1 M (NaCl + HCl) in the range of pH 0.7–4.7 was measured. In 1 M NaNO3 solutions at pH 4.7–3.0 for I and 4.3–3.9 for II, the formal potentials are constant: 0.820 and 0.730 V, respectively. They preserve approximately the same value with a decrease
in pH to 0.7 in 1 M (NaCl + HCl). The potential noticeably decreases with a decrease in the NaNO3 or NaCl concentration from 1 M to 0 (pH 4.1–4.7): to 0.09 and 0.05–0.06 V for I and II, respectively. Approximate constancy of the potential of the U5+/U4+ couple with a decrease in pH to 1 and lower distinguishes this couple from the M4+/M3+ couples (M = Ce, Am, Bk) whose potential appreciably grows with increasing acidity. This is due to the fact that the U5+ and M4+ ions in acid solutions remain in the form of complexes with the ratio M: HPA = 1: 2, whereas the M3+ ions pass into the form of 1: 1 complexes. Thus, variation of the formal potentials of all the M
n + 1/M
n+ couples in the presence of H+ and Na+ ions is associated with variation of the stability constants of the complexes M(HPA)2, which, in turn, is caused by interaction of single-charged ions with HPA. However, the H+ and Na+ ions interact with HPA by different mechanisms and therefore affect the potential of the U5+/U4+ couple differently.
Original Russian Text ? V.P. Shilov, A.B. Yusov, A.M. Fedoseev, Ph. Moisy, 2008, published in Radiokhimiya, 2008, Vol. 50,
No. 5, pp. 393–396. 相似文献
286.
The equilibrium of the reaction U(VI) + 2Ce(III) ⇄ U(IV) + 2Ce(IV) in the presence of unsalurated heleropoly compounds K10P2W17O61 and K8SiW11O39 in 0.01–1.0 M HClO4 solutions (ionic strength 1) was studied. The potential of the Ce(IV)/Ce(III) couple in K8SiW11O39 solutions was measured, from which the overall stability constants β2IV of the complexes UIV(SiW11O39)212−, equal to 1023.8 and 1019.8 in 0.1 M HClO4 + 0.9 M NaClO4 and in 1.0 M HClO4, respectively, were calculated. Under the same conditions, for the complex UIV(P2W17O61)216− β2IV = 1023.2 and 1018.5 (the latter value was obtained by extrapolation or data for 0.1 M HClO4 + 0.9 M NaClO4 solution).
Original Russian Text ? V.P. Shilov. A.B. Yusov, M.N. Sokohva. A.M. Fedoseev, 2008, published in Radiokhimiya, 2008, Vol.
50. No. 3, pp. 203–208. 相似文献