Radiohochspannungsionophoretische Untersuchungen der Isotopenaustauschreaktionen zwischen Polythionaten,Thiosulfat und Sulfit

The isotopic exchange of³⁵S between thiosulfate/sulfite and tetrathionate/thiosulfate is examined. The kinetic data are determined. In both cases the reactions are of second order. As the isotopic exchange between tetrathionate/thiosulfate is very fast, these reaction components are used in high dilution. Furthermore, the extent of exchange during the separation is determined.      

Komplexometrische Folgetitrationen von Eisen und Nickel sowie Kupfer und Nickel imμg-Bereich

Zusammenfassung Eine quantitative Bestimmungsmethode für Mikromengen Eisen und Nickel sowie Kupfer und Nickel, wie sie in Legierungen, Oxidgemischen und galvanischen Bädern vorkommen, wurde beschrieben. Die Metalle werden komplexometrisch mit ÄDTA und Kupferstandardlösung unter Verwendung einer kupferionensensitiven Elektrode und potentiometrischer Äquivalenzpunktindikation bestimmt. Eisen bzw. Kupfer werden direkt mit ÄDTA titriert, das Nickel dann in der gleichen Lösung durch Rücktitration des überschüssigen ÄDTA mit Kupferstandardlösung bestimmt.Die relativen Standardabweichungen der Bestimmungen liegen für Eisen bei ±(0,6 bis 1,2)%, für Kupfer bei ±(0,4 bis 0,8)% und für Nickel bei ±(0,6 bis 1,2)% jeweils für den Bereich von 800g bis 25g Metall. Unter den gewählten Bedingungen lassen sich mit dem Verfahren noch 25g Eisen, Kupfer bzw. Nickel bestimmen.

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Complexometric sequential titrations of iron and nickel as well as copper and nickel in theg range

Summary A quantitative assay method was described for microamounts of iron and nickel such as occur in alloys, oxide mixtures and galvanic baths. The metals were determined complexometrically with EDTA and standard copper solution using an electrode sensitive to copper ions and potentiometric indication of the equivalence point. Iron and copper were titrated directly with EDTA, and nickel then determined in the same solution by back-titration of the excess EDTA with standard copper solution.The relative standard deviations of the assays are ±(0.6–1.2)% for iron, at ±(0.4–0.8)% for copper, and at ±(0.6–12.2)% for nickel for the range from 800–25g metal respectively. Under the conditions chosen, 25g of iron, copper or nickel can be determined using the procedure.

     

Direkte photometrische Bestimmung von Kobalt in Eisen, St?hlen, Erzen und Schlacken mit Nitroso-R-Salz

Zusammenfassung Die direkte Bestimmung von Kobalt in unterschiedlichen Substanzen im Gehaltsbereich von 0,001 bis 5% ist nach einem einfachen Verfahren möglich, wenn die Komplexbildungsreaktion und der tatsächliche Störeffekt durch andere Elemente bekannt sind. Die für eine Bestimmung benötigte Zeit beträgt 25 min. Die relative Standardabweichung liegt zwischen 0,02–20%.

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Direct photometric determination of cobalt in iron, steels, ores and slags using nitroso-R-salt

A simple procedure without any separation is described; the complex formation and the interfering effects of other elements are studied. This method is suitable for the accurate determination of 0.001 to 5% of cobalt in several materials. The time required for one determination is 25 min only. The coefficients of variation are within 0.02–20%.

     

pH-Dependent force spectroscopy of tri(ethylene glycol)- and methyl-terminated self-assembled monolayers adsorbed on gold

Self-assembled monolayers (SAMs) of methoxy-tri(ethylene glycol)- (EG(3)-OMe) and methyl-terminated alkanethiols (C(16)) adsorbed on polycrystalline gold were investigated by chemical force spectroscopy. Measurements were performed in aqueous electrolyte solutions depending on ionic strength and pH value. Charged and hydrophobic tips were employed as probes to mimic local patches of proteins and to study the interaction at the organic/liquid interface in detail. Force-distance curves reveal information about the origin of the observed interaction and the underlying mechanisms. The measurements confirm an effective negative surface charge to be present at the oligo(ethylene glycol) (OEG) and the methyl interface and suggest that the charges are due to the adsorption of hydroxyl ions from aqueous solution. pH-dependent measurements further support the robustness of the established charge associated with the OEG films. Its sign does not change over the whole range of investigated values between pH approximately 3.5 and approximately 10. In contrast, the hydrophobic self-assembled hexadecanethiol films on gold show an isoelectric point (IEP) around pH 4. While the mechanism of charge establishment appears to be similar for both SA films, the strength of hydrogen bonding to interfacial water, which acts as a template for hydroxyl ion adsorption, is likely to be responsible for the observed difference.     

Elevated plasma levels of haptoglobin in Duchenne muscular dystrophy:electrophoretic variants in patients with a severe form of the disease

Analysis of plasma proteins of Duchenne muscular dystrophy (DMD) patients and normal age-matched boys using two dimensional gel electrophoresis and densitometry indicated a three-fold increase in the average haptoglobin level in DMD plasma. Two electrophoretic variants of haptoglobin in which the alpha 2 chain had more basic or more acidic spots were found in DMD patients with a rapidly progressing form of the disease. The basic variant was present in relatively low amount. Possible reasons for the elevated haptoglobin levels are discussed.     

Catecholamine binding to CNS adrenergic receptors.

The properties of 3H-catecholamine binding to alpha- and beta-adrenergic receptors in CNS are reviewed. 3H-epinephrine and 3H-norepinephrine label one class of alpha-receptors throughout the brain, with high affinities for agonists and some antagonists. Agonist affinities at this site are increased in low temperature conditions but are reduced by guanine nucleotides and monovalent cations. Divalent cations reverse both effects. This alpha-receptor may be coupled to adenylate cyclase by GTP and/or sodium, and uncoupled by divalent cations. 3H-epinephrine labels beta2, but not beta1, receptors in CNS, especially in bovine cerebellum. The same beta-receptor does not show agonist-specific GTP-sensitivity, but does exhibit Na+-sensitivity. This receptor appears to be linked to adenylate cyclase, and sodium rather than GTP may be the coupling agent.     

Studium des gegenseitigen Einflusses der Bindungen in Thiocyanat-Kupfer(II)-Komplexen mit Methyl- und Dimethylpyridinen mittels Infrarotspektroskopie

The infrared spectra of thiocyanato-copper(II) complexes of the type Cu(NCS)₂ L ₂ with all isomeric picolines and lutidines (L) as well as those of the type Cu(NCS)₂ L ₃ withL=3- and 4-picoline, 3,4- and 3,5-lutidine were measured. The behaviour of the (CN) stretching vibrations of the Cu(NCS)₂ L ₂ complexes led to conclusions on the different kind of coordination of the NCS groups in dependence on the ligandL. The mutually conditioned strength of the Cu–NCS and Cu–N(L) bonds in the equatorial plane, especially in the presence of ligandsL with the steric effect, was determined from the frequency shift of the Cu–NCS and Cu–N(L) stretching vibrations with regard to the vibrations for Cu(NCS)₂(pyridine)₂.

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Die Massenspektren der Pyrrolidide einiger aliphatisch-alicyclischer Carbonsäuren

The mass spectra of the pyrrolidides of some long-chain carboxylic acids with alicyclic residues attached to their ω-end are discussed and compared with the spectra of the corresponding esters. Fragmentation triggered by the pyrrolidide group generates a series of peaks, which clearly exhibits the size and the structure of the carbon chain.     

Recherches dans la serie des metallocenes—XXVII: Stereochimies comparees de ferrocenylcyclohexenones chirales portant un carbone asymetrique quaternaire en position α ou β. Puretes optiques par dilution isotopique

The two diastereoisomeric pairs of α-phenyl α-methyl and β-phenyl β-methyl ferrocenyl cyclohexenones were prepared in optically active series from a single chiral precursor, (+) phenyl-2 methyl-2 succinic acid, the S configuration of which was established by chemical correlation. The chiral precursor and the four ketones were shown to be optically pure by isotopic dilution with tritium labelled racemates. We infer that diastereogenic cyclisation of the γ-ferrocenyl butyric acids into ketones is under pure kinetic control and leads mainly to the isomer bearing the bulkiest group in an endo position.     

A new approach to intermolecular forces in non-bonding regions

A new method to compute intermolecular energies in non-bonding regions is presented. It is based on the assumption that in such regions molecules can be reviewed as the sum of distorted, possibly overlapping, and electron exchanging atoms. The intermolecular energy change at a given distance is due to the sum of the atomic energy changes caused by these distortions. The energy change of any particular atom is computed in a Hartree—Fock model in which the effect of the other atom is represented by an effective potential. This potential in turn is computed from a calculation at a slightly larger intermolecular distance of the potential seen by an external electron in the field of the “other” atom. This potential computed in the RPA approximation and involves the distorted Hartree—Fock orbitals of the other atom (computed in a similar manner to the above) and the RPA response function of the other distorted atom.