Kalorimetrische untersuchung flüssiger indium—kadmium-legierungen unter dem aspekt von assoziationsgleichgewichten

Enthalpies of mixing of liquid In—Cd alloys were determined over the entire concentration range using a sensitive calorimeter. Deviations of this system from regular behavior can be explained by the existence of associates in the alloy melts. Furthermore the concentration dependence of the enthalpies of mixing were explained, with the help of a previously derived model, by the existence of associates of the composition InCd₃. Moreover the possibility was discussed that associates of a different stoichiometric composition occur in liquid In—Cd alloys, by which the discrepancies of earlier experimental results with the isopiestic method can be clarified.     

Hochtemperatur-kalorimeter zur genauen bestimmung von mischungsenthalpien

A high-temperature calorimeter is described which permits the measurement of mixing enthalpies of liquid alloys and of solution enthalpies of solid alloys at temperatures ranging up to 1000°C. The suitability of the apparatus is shown by its application to the measurement of the mixing enthalpies of the liquid alloys in the indium-antimony system.     

Catalytic stereoselective synthesis of α-Amino phosphonic acid derivatives by asymmetric hydrogenation

The phosphonate analogue of α-N-benzoyl protected phenylalanine methylester has been prepared by catalytic synthesis. Commonly used Rh-complexes has been applied in asymmetric hydrogenation to check their usefulness in the standard reaction.     

Quantitative determination of ultra-traces of chlorinated compounds in high-volume air samples from the Arctic using polyurethane foam as collection medium

Summary A method has been developed for the determination of very low concentrations (pg/m³) of organic chlorinated compounds in air. Chlorinated benzenes, hexachlorocyclohexanes, polychlorinated biphenyls and the DDT group. Since most of the atmospheric burden of such compounds occurs in the gas phase, a high volume sampling method has been developed using carefully precleaned polyurethane foam as collection medium. Samples of 2000–4000 m³ were taken at different sites in the Arctic. The foam quality as well as the precleaning procedure of the foam and the clean-up of the sample are described in detail. The recovery of both the extraction and sample pretreatment was in the range of 80–115% for nanogram amounts. Sampling efficiency for the first foam plug was 80–100%.The sampling efficiency is influenced by different factors (temperature, air humidity, sampling volume). For quantification and identification, the highly selective methods of negative ion chemical ionization mass spectrometry and electron capture detection were combined with high resolution gas chromatography. The detection limit of the method was for most compounds less than a few pg/m³. Some preliminary data from the Arctic measurements are presented and are briefly discussed.

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Quantitative Bestimmung von Ultraspuren chlorierter Verbindungen in großvolumigen Luftproben aus der Arktis mit Hilfe von Polyurethanschaum als Sammelmedium

Zusammenfassung Das beschriebene Verfahren dient zur Bestimmung von chlorierten Verbindungen (chlorierte Benzole, Hexachlorcyclohexane, polychlorierte Biphenyle, DDT-Gruppe) in niedrigen Konzentrationen (pg/m³) in Luft. Da die meisten dieser Verbindungen gasförmig vorkommen, wurde eine Probenahmemethode für große Volumina unter Verwendung von sorgfältig vorgereinigtem Polyurethanschaum als Adsorptionsmedium entwickelt. Proben von 2000–4000 m³ wurden an verschiedenen Stellen der Arktis genommen. Die Vorbehandlung des Schaums und der Probe wird ausführlich beschrieben. Bei ng-Mengen lag die Wiederfindung bei 80–115%. Die Leistungsfähigkeit der ersten Schaumschicht lag bei 80–100%. Durch Temperatur, Luftfeuchtigkeit und Probenahmevolumen wird die Leistungsfähigkeit beeinflußt. Zur Identifizierung und quantitativen Bestimmung wurde die Negativionen-Massenspektrometrie mit chemischer Ionisation und die EC-Detektion mit der Hochleistungs-Gas-Chromatographie kombiniert. Die Nachweisgrenze lag für die meisten Verbindungen bei weniger als einigen pg/m³. Einige Daten der arktischen Messungen werden vorgestellt und kurz diskutiert.

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Partly presented at the Fourth European Conference on Analytical Chemistry, Helsinki/Espoo, Finland 1981     

Second class currents and broken SU(3)-symmetry

In the SU(3) limit, a second class, T-normal axial vector current, which transforms like an octet, can give rise to pseudotensor terms in the matrix elements for leptonic decays of baryons. With first order symmetry breaking, this second class current may generate pseudovector and pseudoscalar form factor contributions. It is an anti-hermitian current, but, even with SU(3) breaking, it does not need to disturb the chiral SU(2) × SU(2) algebra of charges.     

Interference in anodic stripping voltammetry from the Teflon vessels used in pressurized digestion

The insufficient inertness of Teflon vessels towards acids at high temperature and pressure is shown to be the source of some interferences in anodic stripping voltammetry. To avoid such problems the use of Pyrex glass inserts in Teflon-lined steel bombs is proposed for the determination of non-volatile heavy metals. The procedure is easily applied to commercially available digestion bombs. Blank values and recovery tests for blood samples spiked with Cd, Pb and Cu are given, and the completeness of the digestion has been checked.     

Evidence for negative cross correlations in vibrational dephasing in liquids: isotropic raman-line shift and width phenomena in isotopic mixtures of N2 and O2

To experimentally confirm the hypothesis of negative cross terms between different dephasing mechanisms, potentially leading to a broadening of the isotropic Raman line upon isotopic dilution, we present a detailed study on the concentration dependencies of all of the line shifts and widths in the four isotopic mixtures of type (15N14N)(x)-(14N2)(1-x), (15N2)(x)-(14N2)(1-x), (15N2)(x)-(15N14N)(1-x), and (16O2)(x)-(18O2)(1-x) near the normal boiling point of nitrogen at T = 77.35 K. A quite disparate behavior of the nitrogen oscillators compared to the oxygen oscillators was observed in respect to a change of their isotopic baths.