The reduction and determination of small amounts of rhenium-VII

Summary Investigations on the reduction of rhenium-VII to rhenium-V have been carried out. The use of stannous chloride in hydrochloric acid solution was not found suitable as the basis for the quantitative determination of the element. The most satisfactory reductant was found to be bismuth amalgam in 18N sulphuric acid. A method is outlined for the determination of milligram amounts of rhenium ranging from 0.1 to 10 mg with a standard deviation of ± 0.02 mg, using this as a basis. The procedure, with only slight modification, can be extended to the determination of microgram amounts of the element.Measurement of absorption spectra indicates that in hydrochloric acid solution a complex is formed between the acid and rhenium-V, but that the stabilisation of rhenium-V by oxalic acid does not arise from the formation of a complex.

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Zusammenfassung Untersuchungen über die Reduktion von Rhenium(VII) zu Rhenium(V) wurden durchgeführt. Zinn(II)-chlorid in salzsaurer Lösung bewährt sich für die quantitative Bestimmung des Rheniums nicht. Als bestes Reduktionsmittel erwies sich Wismutamalgam in 18-n Schwefelsäure. Auf dieser Basis wurde ein Verfahren zur Miüigrammbestimmung von Rhenium ausgearbeitet, das im Bereich zwischen 0,1 und 10 mg Abweichungen von ± 0,02 mg zeigt. Mit nur geringen Abänderungen läßt es sieh auch zur Bestimmung von Mikrogrammengen verwenden.Messungen der Absorptionsspektren ergaben, daß sich in salzsaurer Lösung ein Komplex aus Säure und Rhenium(V) bildet, daß aber die Stabilisierung des 5wertigen Rheniums durch Oxalsäure nicht auf der Bildung eines Komplexes beruht.

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Résumé Recherches sur la réduction du rhénium VII en rhénium V. On a établi que la solution de chlorure stanneux dans l'acide chlorhydrique n'est pas un réactif approprié à la détermination quantitative de l'élément. On a montré que le réducteur le plus satisfaisant était l'amalgame de bismuth dans l'acide sulfurique 18 N. Les auteurs esquissent une méthode basée sur l'emploi de ce réactif pour le microdosage du rhénium en quantités variant de 0,1 à 10 mg avec un écart type de ± 0,02 mg. La technique légèrement modifiée peut être étendue au dosage de quantités de l'ordre de grandeur du microgramme.Les mesures de spectres d'absorption montrent qu'en solution d'acide chlorhydrique il se forme un complexe entre l'acide et le rhénium V mais que par contre la stabilisation du rhénium V par l'acide oxalique ne résulte pas de la formation d'un complexe.

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To Professor Dr.Hans Lieb, University of Graz, for his 70th birthday.

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One of us (H. S.) would like to take this opportunity to thank the Department of Chemistry of the Queen's University of Belfast for the facilities granted in carrying out this work.     

Kinetics of the solvolysis of thetrans-dichlorobis (Diaminoethane)-cobalt(III) ion in aqueous ethylene carbonate and aqueous propylene carbonate

The kinetics of the solvolysis of trans-[Coen₂Cl₂]⁺ have been followed in mixtures of water with either ethylene carbonate or propylene carbonate over a range of temperatures. Both the enthalpy and entropy of activation for the first order loss of a chloride ion to give [Coen₂Cl]²⁺ in water + ethylene carbonate show a maximum at low mole fractions of ethylene carbonate. As similar extrema in H and S for the same process for this complex and others in water +2-propanol and in water + t-butanol correlate well with extrema in the physical properties of the mixtures which are influenced by changes in solvent structure, it is suggested that these new extrema can be attributed to solvent structure effects. The application of a free energy cycle to the loss of the chloride ion in water and in the mixtures suggests that, although changes in solvent structure influence the cation in the transition state more than the cation in the initial state in water + ethylene carbonate, in water + propylene carbonate the influence of changes in solvent structure approximately balances. This is compared with the application of the free energy cycle to the same process in mixtures of water with a range of cosolvents using kinetic data available in the literature.     

Determination of transition temperatures and crystalline content of linear,high-molecular-weight polyethylene by proton NMR spectroscopy

Decomposition of the proton NMR spectra of linear, high-molecular-weight polyethylene into a Gaussian function and a Lorentzian function is discussed in terms of the Wilson-Pake two-component method for an inhomogeneous system. The results of a Goldman-Shen experiment indicate that spin diffusion does not strongly couple the two regions. The temperature dependence of the Lorentzian (mobile) fraction is fitted to a function derived from the relation of English and Zoller. The critical temperatures give estimates of thermal transitions: T_α = 328 (± 5) K and T_γ = 163 (± 4) K. The fraction of Lorentzian spins excited by the γ relaxation correlates with the amorphous content of the sample as determined by differential scanning calorimetry and x-ray diffraction.     

Metal-organic complexes of analytical significance : The stabilities of complexes of bivalent metallic ions with anthranilic acid and its derivatives

The insolubility of metal anthranilates and related chelates prevents determination of their stabilities by conventional methods A suitable electrolytic cell has been designed with which E.M F. measurements have been made. The results obtained enable stabilities, heats of formation and entropies of formation to be derived These are discussed in relation to the structures of the complexes.     

Infrared spectra for the identification of some inorganic anions using nitron as precipitant

Summary Using infrared absorption spectroscopy a method has been developed which permits the identification, either singly or in admixture, of the following anions: ferrocyanide, ferricyanide, cobalticyanide, chlorate, bromate, perchlorate, periodate, nitrate, nitrite, tungstate, molybdate and chromate. The anions are precipitated by nitron, and using the KBr-disc technique characteristic bands are obtained in the near infrared.

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Zusammenfassung Durch Infrarotabsorptionsspektroskopie lassen sich entweder allein oder in Gemischen folgende Anionen identifizieren: Cyanoferrat(II), Cyanoferrat(III), Cyanokobaltat, Chlorat, Bromat, Perchlorat, Perjodat, Nitrat, Nitrit, Wolframat, Molybdat und Chromat. Die Anionen werden mit Nitron gefällt und geben bei Verwendung einer Kaliumbromid-Linse charakteristische Banden im nahen Infrarot.

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Résumé On a développé une méthode permettant l'identification par spectrographie d'absorption infrarouge des anions suivants, séparément ou en mélanges: ferrocyanure, ferricyanure, cobalticyanure, chlorate, bromate, perchlorate, periodate, nitrate, nitrite, tungstate, molybdate et chromate. On précipite les anions par le nitron et l'on met en évidence les bandes caractéristiques dans l'infrarouge proche, par la technique à la pastille de KBr.

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Dedicated to ProfessorA. A. Benedetti-Pichler on the occasion of his 70th birthday.

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One of us (S. A. E. S.) acknowledges gratefully the award of a scholarship from the U. A. R. Government, which has enabled him to take part in this work.     

The Taylor map on complex path groups

Let W(G) denote the path group of an arbitrary complex connected Lie group. The existence of a heat kernel measure νt on W(G) has been shown in [M. Cecil, B.K. Driver, Heat kernel measure on loop and path groups, preprint, http://www.math.uconn.edu/~cecil/papers/p2.pdf; Infin. Dimens. Anal. Quantum Probab. Relat. Top., submitted for publication]. The present work establishes an isometric map, the Taylor map, from the space of L²(νt)-holomorphic functions on W(G) to a subspace of the dual of the universal enveloping algebra of Lie(H(G)), where H(G) is the Lie subgroup of finite energy paths. This map is shown to be surjective in the case where G is a simply connected graded Lie group.     

Droplet imaging velocimeter and sizer: a two-dimensional technique to measure droplet size

This paper discusses the droplet imaging velocimeter and sizer (DIVAS), a two-dimensional technique to measure droplet size from very small droplets (a few microns) to very large drops (millimeters), as well as droplet velocity and concentration. DIVAS uses a particle imaging velocimetry (PIV) configuration; that is, pulsed lasers illuminate the droplets in the measurement plane and CCD cameras collect the off-axis scattered light, thus yielding a small measurement volume and correspondingly a high number density measurement capability. DIVAS is based on glare point imaging as described by van de Hulst and Wang (Appl Opt 30(33):4755–4763, 1991). By measuring the separation of cross-polarized glare points, DIVAS is capable of measuring droplet size down to a few microns with sub-pixel resolution. The measurement of large drops from the separation of glare points is straightforward. However, the paper discusses that large drops are often non-spherical and more advanced signal processing is required to retrieve their size. Both analytical studies and experiments are presented to demonstrate the feasibility of the technique.     

Dimension-Independent Estimates for Heat Operators and Harmonic Functions

We establish dimension-independent estimates related to heat operators e ^tL on manifolds. We first develop a very general contractivity result for Markov kernels which can be applied to diffusion semigroups. Second, we develop estimates on the norm behavior of harmonic and non-negative subharmonic functions. We apply these results to two examples of interest: when L is the Laplace–Beltrami operator on a Riemannian manifold with Ricci curvature bounded from below, and when L is an invariant subelliptic operator of Hörmander type on a Lie group. In the former example, we also obtain pointwise bounds on harmonic and subharmonic functions, while in the latter example, we obtain pointwise bounds on harmonic functions when a generalized curvature-dimension inequality is satisfied.