Bestimmung des Urangehaltes und der UO2-Stöchiometrie in ThO2-UO2-Kernbrennstoffen

Analysis for uranium and UO₂ stoichiometry in 2.5–5% UO₂ containing ThO₂-UO₂ fuels is made in a single procedure by controlled-potential coulometry. Samples are dissolved in phosphoric acid-hydrofluoric acid with the addition of Al₂(SO₄)₃. With sample weights from 0.2 to 2 g the uranium content is determined with a relative standard deviation of 1%. The minimum detectable hyperstoichiometry of UO₂ amounts to 2.004 with a standard deviation of 0.002.     

Potentiometric Determination of Ascorbic Acid: Estimation of Its Contribution to the Total Antioxidant Capacity of Plant Materials

It was found that an iodine-modified platinum electrode gives a linear potentiometric response to 1.0 × 10^–5 to 1.0 × 10^–3 M ascorbic acid in model solutions. Ascorbic acid in some preparations was determined by potentiometry. The contribution of ascorbic acid to the total antioxidant capacity of aqueous extracts of hips, hop cones, and lemon juice was estimated.     

Thermal analysis — A guide to the optimization of sintering processes

During the sintering of multicomponent disperse systems prepared from mixtures of the components, a variety of solid-state reactions, phase formation or dissolution, and the occurrence of a liquid phase determine the densification and the final microstructure of the material.The results are presented of investigations on the systems WC-Co and Fe-Si, through the simultaneous application of dilatometry, differential thermal analysis and thermogravimetry, coupled with metallographic and microprobe analysis.

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Zusammenfassung Beim Sintern vielkomponentiger Systeme, die aus Gemischen der Komponenten hergestellt werden, bestimmt eine Vielzahl von Festkörperreaktionen, Neubildung und Auflösung von Phasen und das Auftreten von flüssigen Phasen die Verdichtung und die erreichbare Mikrostruktur des Materials.Ergebnisse der Untersuchung in den Systemen WC-Co und Fe-Si durch kombinierten Einsatz von Dilatometrie, TG-DTA, metallographischen und Mikrosonden-Untersuchungen werden mitgeteilt.

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, , , . WC- Fe-Si , , .

     

Analysis of ion binding on humic substances and the determination of intrinsic affinity distributions

Humic substances are characterized by a variable electric potential and by a variety of binding sites leading to chemical heterogeneity. Binding of ions to these substances is influenced by both factors. A methodology based on acid—base titrations at several salt levels is presented that allows for the assessment of an appropriate electrostatic double-layer model and the intrinsic proton affinity distribution. The double-layer model is used for the conversion of pH to pH_S for each data point, where H_S is the proton concentration in the diffuse layer near the binding site. It is shown that with an appropriate double-layer model the proton binding curves at different salt levels converge into one “master curve” when plotted as a function of pH_S. The intrinsic proton affinity distribution can then be derived from the “master curve” using the LOGA method. A rigorous analysis of metal binding to humic substances is complex and in practice is not feasible. Under two different (simplifying) assumptions, namely fully coupled and uncoupled binding, it is shown how intrinsic metal ion affinity distributions can be obtained. Model calculations show that apparent metal ion affinity distributions do not resemble the intrinsic metal ion affinity distribution.     

Organolithium and organosodium compounds of n-substituted 2-alkylbenzimidazoles

Organolithium and organosodium compounds of 1,2-dimethyl-, 1-methyl-2-ethyl-, 1-methyl-2-propyl-, and 1-phenyl-2-methylbenzimidazole, containing the metal in the alkyl group at position C(₂), were obtained by metallation. It was found that metallation can be complicated by the addition of the metalling reagent at the C=N bond of the heterocycle. It was shown that the obtained organometallic compounds can be used for the synthesis of various derivatives of benzimidazole.The calculation was performed with the standard bond lengths. A planar model was used for the carbanion.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1073–1077, August, 1986.     

Isolation of nonprotamine proteins from the nuclei of the gonad cells of the Russian sturgeonAcipenser güldenstadti

Eight nonprotamine proteins have extracted from the nuclei of the cells of the gonads of the Russian sturgeon with 0.35 M sodium chloride solution followed by fractionation of carboxymethyl-Sephadex G-25 and desalting on Bio-Gel P-2, and their amino acid compositions have been determined.     

Bestimmung von Spurenelementen in Staubproben durch Röntgenfluorescenzanalyse mit Radionuklidanregung unter besonderer Berücksichtigung der Matrixeffekte

The analysis of dust samples by X-ray fluorescence using Cd-109 as X-ray source is described. For calibration silica gel standards are used. The correction for matrix effects is carried out by means of the Compton peaks. Besides the elements K, Ca, Ti, Fe, Rb, Sr, Y, Zr, which may be considered to be natural components of the ground, the elements Cr, Mn, Ni, Cu, Zn, Br and Pb are determined in the dust samples.     

Spectrophotometric determination of zirconium with 9-methyl-2,3,7-trihydroxy-6-fluorone

Summary 9-Methyl-2.3.7-trihydroxy-6-fluorone has been used as a new colorimetric reagent for zirconium. The rose-red complex shows maximum absorption, against the reagent blank, at 500 nm and obeys Beer's law from 0.1 to 2.5 ppm. The optimum concentration range is from 0.66 to 2.5 ppm, where the per cent relative analysis error is 2.96. The composition of the complex, obtained from Job's method, indicates that the complex in solution contains the metal and the reagent in a ratio of 11. The instability constant of the complex is 1.07 · 10^–6.