Bestimmung der Trichloressigs?ure durch Absorptions- und Fluorescenzmessung

Zusammenfassung Für die Rückstandsanalyse der als Herbicid verwendeten Trichloressigsäure (TCA) wurde eine Methode sowohl für die Absorption- sals auch für die Fluorescenzmessung entwickelt. TCA wird im stark alkalischen Milieu zu Chloroform abgebaut und mit Pyridin zu einer Schiffchen Base umgesetzt (Fujiwara-Reaktion). Diese rote instabile Verbindung wird mit Barbitursäure in einen beständigen Pentamethinfarbstoff überführt, dessen Absorptionsmaximum bei 594 nm liegt. Als Untersuchungsmaterial dienten Bodenproben. Bei einer Einwaage von 100 g Boden lassen sich noch 0,1 ppm TCA nachweisen. Durch Fluorescenzmessung (Anregungsmaximum 588 nm, Emissionsmaximum 611 nm) werden bei gleichen Versuchsbedingungen noch 0,01 ppm erfaßt.

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Determination of trichloroacetic acid by absorption spectrometry and fluorometry

Summary A method for absorption and fluorescence measuring of the residues of trichloroacetic acid (TCA) used as herbicide was developed. TCA was decarboxylated with strong alkali and converted with pyridine to a Schiff's base (Fujiwara reaction). After the reaction of the Schiff's base with barbituric acid a stable pentamethin dyestuff was formed. The maximum absorbance occurs at 594 nm. Samples of soil were analysed. In a sample of at least 100 g 0.1 ppm of TCA are still detectable. By fluorometry (excitation maximum 588 nm, emission maximum 611 nm) the detection limit is at 0.01 ppm under the same conditions.

     

The nonlinear shear gradient effect on the shear viscosity of a ternary system near a plait point

We have studied the shear viscosity of a ternary liquid mixture (water-ethanol-chloroform) near a plait point by the capillary method and found an apparently strong levelling-off as we approach the critical point. This levelling-off cannot be explained simply in terms of a strong cusp. It is found that the nonlinear shear gradient effect suggested by Oxtoby can be used to explain this behavior.     

Exchange of deuterium with OH groups of HY zeolites

The exchange reaction of D₂ with OH groups of HY zeolites was followed both in the solid and gas phase by IR and MS. The rates of D₂–OH and D₂–H₂ exchange increase considerably with dehydroxylation of the sample. The active centers are probably vacancies formed by removal of oxygen from the lattice, they catalyze the dissociation of D₂. Dehydroxylation of the sample is accompanied by the formation of 3 740 cm^–1 hydroxyls, whose exchange with D₂ is slower than that with other OH groups and which affect the kinetics in the gas phase.

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D₂ OH HY - O₂–OH O₂–H₂ . , , , O₂. OH, 3740 ^–1, , OH .

     

Gamma radiolytic decomposition of solid binary mixtures of potassium nitrate with halides

Gamma-ray induced decomposition of solid binary mixtures of KNO₃ with halides viz. KCl, KBr and KI has been studied at room temperature. G(NO ₂ ^– ) values were found to vary with absorbed dose. Size and electronegativity of anions and molar composition of halides are the other factors influencing radiolysis.     

Zur Entwicklung der Oberflächenrauhigkeit während des Sputterns

Zusammenfassung Die zeitliche Entwicklung der Mikrorauhigkeit einer Oberfläche während des Sputterns wurde für verschiedene Größen der Oberflächendiffusionskoeffizienten untersucht. Das Modell berücksichtigt die Bedeckungsgradabhängigkeit der Diffusionsweglänge. Effekte der Korrelation zwischen Atomen beim Sputtern wurden diskutiert. Es wurde gezeigt, daß ab einem Schwellenwert des Oberflächendiffusionskoeffizienten die Tiefenauflösung nahezu konstant wird, statt mit der Quadratwurzel der Sputtertiefen anzuwachsen.

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The development of surface roughness during sputtering

Summary The time-dependence of the micro roughness of a surface during sputtering is investigated for various values of the coefficient of surface diffusionD _s using a model of a coverage dependent diffusion length. Effects of correlation between atoms within the sputtered layer are discussed. It is shown that beginning at a threshold value ofD _s the depth resolution of sputtering becomes a constant instead of being proportional to the square root of the sputter depth.

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Vorgetragen beim 10. Kolloquium über metallkundliche Analyse, Wien, 3.-5. November 1980. -Herrn Prof. Dr. Hanns Malissa zum 60. Geburtstag gewidmet.     

Raman spectra of glassy aqueous LiX and CaX2 solutions (X = Cl,Br and I) in the low frequency region

Raman spectra of glassy aqueous LiX and CaX₂ solutions are obtained in the low frequency region (10–900 cm^?1). Two low frequency Raman bands are clearly observed. A qualitative discussion is given for the intensity correlation and observed frequency shifts of these bands with halide ions.     

Electrochemical investigations of amino acids at solid electrodes: Part I. Sulfur components: Cystine,cysteine, methionine

The electrochemical oxidation of sulfur amino acids has been investigated by ac measurements and cyclic voltammetry at solid electrodes (Au, vitreous carbon). Electrochemical oxidation proceeds first in the adsorbed state and second by diffusion at metal electrodes. Electrochemical oxidation is catalyzed by a labile metal oxide. At vitreous carbon electrode oxidation in the adsorbed state is only present in the case of methionine. XPS studies have shown the presence of

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as intermediate species. To explain the experimental results a reaction path is proposed.     

The extraction of HCl by TDPO in benzene

The results of the extraction of HCl by TDPO in benzene and the co-extraction of water are discussed. From the infrared spectra of normal (HCl-H₂O) and deuterated (DCl-D₂O) systems it may be concluded that TDPO·HCl·H₂O is formed in the organic phase on extraction from aqueous solutions with c_HCl≤5M, and TDPO·HCl with c_HCl>5M. Compounds such as TDPO·2HCl are found in the organic phase if there is an excess of HCl in the organic phase. From cryoscopic and viscosity measurements of the organic phase, conclusions can be made about the presence of polymeric compounds in this phase.     

Distribution de la densite des electrons de valence dans Cu2As

The distribution of valency electron density in Cu₂As (C38) has been determined by Fourier synthesis using as coefficients the values ΔF = F_obs ? F_core (F_core corresponds to the structure factors of the inner orbitals). The bonding between the pyramidal-site copper atoms and the arsenic atoms is exposed, as well as the bonding between tetrahedral-site and pyramidal-site copper atoms.The structural evolution of the unit cell from the Cu₂Sb-type (C38) to the Fe₂P-type (C22) and Co₂P-type (C23) can be related to the metal-metalloid interaction. This interaction mainly involves the pyramidal-site metal atoms in the Cu₂Sb-type, and the tetrahedral-site metal atoms in the Fe₂P- and Co₂P-types.     

Alpha and deuteron induced reactions on vanadium

The stacked foil technique was used in combination with γ-ray spectroscopy to obtain excitation functions for the production of different nuclei using natural vanadium as target and 85 MeV α-particles and 46.5 MeV deuterons as projectiles. The data are compared with theoretical predictions provided by an equilibrium and pre-equilibrium reaction model. In most cases the theoretical predictions seriously under-estimated the measured cross sections.