Kinetics of the hydrogen electrode reactions of platinum in the NaHSO4 + KHSO4 eutectic melt

The kinetics of the hydrogen electrode reactions on Pt in the NaHSO₄ + KHSO₄ melt at ca. 185°C is studied. Under potentiodynamic conditions both the anodic and cathodic processes can be interpreted with the hydrogen electrode reaction mechanism already known. At potentials more negative than 0.1 V (vs. Ag/Ag⁺ (0.06 M)) the mechanism of the cathodic reaction changes because of a sulphide species formed on the electrode which is produced by a reduction of the melt components.     

The oils of some plants of the family Malvaceae

Summary 1. The physical and chemical properties and the fatty-acid and glyceride compositions of the oils of four plants of the family Malvaceae have been studied. They all belong to the palmito-oleo-linoleic group.2. Their glyceride structure does not correspond to the principle of statistical distribution, since almost all the unsaturated-acid radicals are concentrated in the position.Order of the Red Banner of Labor Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 252–255, May–June, 1971     

Rock porosity determination by combination of X-ray computerized tomography with mercury porosimetry

First results are described of coupling of mercury porosimetry with X-ray computerized tomography (CT) as a new combination technique for rock porosity studies. This technique is suitable for rock samples with a pronounced mercury intrusion-extrusion hysteresis and includes CT measurements before and after mercury intrusion. The entrapped portion of mercury, when the pressure after the intrusion into the rock sample is reduced to 0.1 MPa, serves as a contrast agent in the porous network to localize spatial distribution of rock porosity by CT. The results obtained show that the mercury intrusion and therefore the porosity were quite different for the separate mineral phases. Therefore the combination of mercury porosimetry and computer tomography can give 3-D data on mineral-specific porosity distributions with additional pore size information. In contrast to mercury porosimetry as a single method, results of the combination technique with CT represent a direct visualization of porosity variation and do not depend on any special pore network model. Received: 2 July 1996 / Revised: 20 November 1996 / Accepted: 22 November 1996     

Quantitation of camphechlor/toxaphene in cod-liver oil by integration of the HRGC/ECD-pattern

Summary Quantitation of camphechlor/toxaphene in biological matrices like cod-liver oil or fish is difficult because it is a very complex mixture of alicyclic polychlorinated compounds. Furthermore, many toxaphene components are biotransformed and photodegraded and the complex mass spectral fragmentation pattern of HRGC/MSD (electron impact (EI)) cannot be used for quantitation at the g/g-level or below. The use of several indicator-peaks after ECD-detection using the technical standard mixture for calibration does not characterize the entire pattern in a biological sample. Two averaging integration methods that are based on the entire HRGC/ECD-pattern of toxaphene compounds after separation from the PCB congeneres by adsorption chromatography on silicagel, allow a fast and accurate quantitation of the mixture in biological samples, e.g. cod-liver oil. Biological degradation does not disturb the determination because the whole pattern of the complex mixture is considered instead of only a few compounds of the parent mixture which could be degraded or not.     

METALLOPURPURINS and LIGHT: EFFECT ON TRANSPLANTABLE RAT BLADDER TUMORS and MURINE SKIN

Purpurins are modified chlorins with photodynamic properties. Their strong absorption in the red region of the visible spectrum makes them candidates for use in photodynamic cancer therapy. A series of metal derivatives of the free base purpurins have been synthesized and shown to cause tumor necrosis in transplantable tumors when exposed to visible light. In the following set of experiments, the effects of two metallo-derivatives (tin and zinc) of two purpurins, octaethylpurpurin (NT2) and etiopurpurin (ET2), and light on the N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide transplantable tumors in Fischer CDF(F344)/CrlBr rats were studied. The photodynamic activity was assessed by a short term assay using tumor dry weight 12 days after purpurin-PDT as a criterion of response. From these experiments it appears that SnET2 greater than SnNT2 greater than ZnET2 greater than ZnNT2 in photodynamic activity. SnET2 was further characterized by attempting to determine the time interval after systemic injection at which maximum therapeutic effect occurred. These studies shown that 24 h after metallopurpurin injection was the optimum time for treatment of tumors with visible light. In a final set of experiments, the effect of solar light on the skin of hairless mice injected with SnET2 was found to be much less injurious than with hematoporphyrin derivative.     

The oxygen evolution reaction on cobalt: Part II. Transient measurements

Open-circuit overpotential decays on an aged cobalt electrode in the oxygen evolution range in 6 M KOH show different slopes for two overpotential regions. These slopes are lower than the Tafel slope in the same region: Tafel slopes of ～100 and ～40 mV/dec, at high and low overpotentials, respectively. compared to decay slopes of ～?60 and ～?20 to ?30 mV/dec. For a fresh cobalt electrode a decay slope of ～?40 mV/dec is found at high overpotentials. From impedance measurements during a decay it is concluded that the electrode capacitance cannot account for the decay curves obsered. By means of steady-state potentiostatic impedance measurements (with stabilization times > 24 h) it is found that the differential Tafel slope remains constant at ～40–50 mV/dec and differs considerably from the Tafel slope at high overpotentials, ～100 mV/dec. Galvanostatic pulse experiments give evidence of the presence of CoO₂ in the oxide layer.Two models which may explain the observed experimental results are analysed. Both include a potential-dependent (extra) process which is fixed by the amount of CoO₂ at the surface. In one model, CoO₂ is responsible for partial surface blockage (parallel process); in the other model, CoO₂ controls the conductivity of the top layer of the oxide layer on the electrode.     

Absolute infrared intensities of hydrocarbons

Dipole-moment derivatives, calculated by both the CNDO/2 method with different parameterizations and the INDO method, are compared to the experimental values determined from absolute infrared intensity measurements for the IR active modes of methane, ethane, ethylene and acetylene. A parameter refinement procedure is introduced in which the CNDO/2 molecular orbital parameters are adjusted through a damped least-squares treatment to give best agreement with the observed dipole-moment derivatives. It is found that the refinement does not substantially improve the agreement obtained with the original CNDO/2 parameterization. The INDO method gives somewhat poorer agreement than the CNDO/2 calculations. As an example of the applicability of the molecular orbital methods toward reproducing relative infrared intensities, the spectrum of cyclopropane in the gasphase is examined.

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Zusammenfassung Die Ableitungen des Dipol-Moments, die nach der CNDO/2-Methode mit verschiedenen Parametrisierungen sowie der INDO-Methode berechnet wurden, werden mit den experimentellen Ergebnissen aus Messungen der absoluten Infrarot-Intensitäten für die IR-aktiven Schwingungen von Methan, Äthan, Äthylen und Azetylen verglichen. Die CNDO/2-Parameter werden mit einer Methode der kleinsten Quadrate den beobachteten Dipol-Moment-Ableitungen angepaßt. Die Ergebnisse sind jedoch nicht wesentlich von denen der ursprünglichen CNDO/2-Methode verschieden. Die INDO-Ergebnisse sind nicht so gut wie die CNDO/2-Ergebnisse. Als Beispiel der Anwendbarkeit der MO-Methoden zur Berechnung von relativen IR-Intensitäten wird das Spektrum des Cyclopropans in der Gasphase untersucht.

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Résumé Les dérivées du moment dipolaire, calculées par la méthode CNDO/2 avec différentes paramétrisations et par la méthode INDO, sont comparées aux valeurs expérimentales déterminées à partir de mesures d'intensité absolue pour les modes actifs dans l'infra-rouge dans le méthane, l'éthane, l'éthylène et l'acétylène. Les paramètres sont ajustés de manière à donner le meilleur accord avec les dérivées du moment dipolaire. Cet ajustement n'améliore pas sensiblement l'accord obtenu avec la paramétrisation CNDO/2 originale. La méthode INDO donne des résultats moins bons que les calculs CNDO/2. Le spectre du cyclopropane en phase gazeuse est étudié comme exemple de l'applicabilité de la méthode des orbitales moléculaires au calcul des intensités relatives infra-rouge.

     

Determination of the chloride content of biological fluids using a chloride-selective electrode

Summary Macromolecular organic compounds do not influence the selectivity of a precipitate-chloride membrane-electrode [2] and therefore, it is possible to determine the chloride content of biological liquids (urine, blood serum) without centrifuging the proteins. The electrode has been used in these determinations for direct measurement or as indicator in argentometric titration. Comparison of the results obtained with that of other methods showed good agreement. For the membrane-electrode method the urine and the serum were diluted 18 and 110, resp.

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Bestimmung des Chloridgehalts in biologischem Material mit Hilfe einer chloridspezifischen Elektrode

Zusammenfassung Makromolekulare organische Lösungsbestandteile beeinflussen die Selektivität der früher beschriebenen [2] Chlorid-Membranelektrode nicht. Deshalb kann mit ihr der Chloridgehalt biologischer Flüssigkeiten (Urin, Blutserum) ohne vorherige Abtrennung der Proteine und anderer organischer Verbindungen bestimmt werden. Die Elektrode dient dabei teilweise zur direkten Messung, teilweise als Indicator bei argentometrischen Titrationen. Ein Vergleich der Ergebnisse mit solchen, die nach der klassischen Methode von Mohr erhalten wurden, beweist die gute Eignung der Elektrode. Es ist zweckmäßig, die Lösungen vor der Analyse im Verhältnis 18 bzw. 110 zu verdünnen.

     

Mass spectra of substituted uracils

The mechanisms for the major fragmentations obtained with selected substituted uracils are discussed. Interpretation of data was facilitated by use of metastable peaks, high-resolution data, and low-voltage spectra. The major fragmentation obtained with N-alkyl substituted uracils, when the alkyl group contains 2 or more carbons, is due to cleavage of the alkyl substituent. This cleavage is accompanied by a rearrangement of 1 or 2 hydrogens from the alkyl group to the uracil ring. Possible mechanisms for the rearrangements are discussed. It was found that the molecular ion of 1- and 3-alkyl substituted uracils (where the alkyl group has 2 or more carbons) does not undergo the expected ‘retro Diels-Alder Reaction’. Instead, the odd-electron ion formed by loss of the alkyl substituent with a single hydrogen rearrangement undergoes this reaction (loses HNCO). Since it is formed as a secondary reaction product, the relative abundance of the ‘retro Diels-Alder’ fragment is low compared to what is obtained in the spectra of the simple uracils. The ‘retro Diels-Alder Reaction’ can be used to differentiate between 2- and 4-thiouracils, and between 1- and 3-methyl and phenyl substituted uracils. It was found that 1- and 3-alkyl substituted uracils (alkyl group of 2 or more carbons) can be differentiated by the mass of the M-alkyl fragment since the 3-substituted compounds give predominantly a double hydrogen rearrangement and the 1-substituted compound gives mainly a single hydrogen rearrangement. In addition the intensity of the molecular ion, relative to the M-alkyl ion, is considerably stronger in the 1-substituted uracils.