Anwendung von mercuriertem Phenolphthalein und Fluorescein in der chemischen Analyse

Zusammenfassung Für die Bestimmung von Quecksilber in den Hg-Komplexen von Phenolphthalein und Fluorescein wird die Titration mit Thioglykolsäurelösung empfehlen. Sie kann direkt oder nach Zerstören des Komplexes mit Brom durchgeführt werden. Das mercurierte Phenolphthalein kam zur Identifizierung gewisser Verbindungen dienen, die eine Farbänderung von Rot nach Blau bewirken und gegebenenfalls bei weiterem Zusatz von Cyanid und Thioharnstoff Farbumschläge bewirken. Die Fähigkeit der Verbindungen, die SH-, NHCS- oder mehrfache NHCO-Gruppen enthalten, die Fluorescenzintensität von Tetraquecksilberacetatfluorescein herabzusetzen, kann zum qualitativen Nachweis und zur quantitativen Bestimmung dieser Verbindungen ausgenutzt werden. Es können sehr kleine Mengen der Verbindungen erfaßt werden und zwar betragen bei Anwendung von 5 ml Lösung die unteren Bestimmungsgrenzenfür: Schwefelwasserstoff 0,02 g, Thioharnstoff 0,04 g, Schwefelkohlenstoff als C₂H₅NHCSSNa 0,02 g, Gelatine 2 g.     

Precision measurement of the conversion electron spectrum of83m Kr with a solenoid retarding spectrometer

This paper reports on precision measurements of conversion lines in the decay of^83mKr with nuclear transition energies of 32.1 keV and 9.4 keV, respectively. The spectra were taken from a submonolayer surface of^83m Kr frozen onto a cold backing, using the new Mainz solenoid retarding spectrometer. The high luminosity and resolution of this instrument enables the observation of all allowed conversion lines up to theN-shell and to fully separate the elastic component from inelastic satellites. The combined analysis of the data yields the transition energiesE _y=32151.5±1.1 eV and 9405.9±0.8 eV, respectively. The experiment served also to pilot the application of this spectrometer to the question of a finite neutrino rest mass, searched for in theβ-decay spectrum of tritium and to problems in precision electron spectroscopy in general.     

Hochspannungselektrophoretische Trennung und Nachweis von Thiolen und Disulfiden

Zusammenfassung Methoden zum Nachweis von Schwefelverbindungen auf Papier unter Verwendung von o-Hydroxymercuribenzoesäure und Dithiofluorescein werden vorgeschlagen. Durch geeignete Kombination dieser Reagentien mit Natriumsulfit, Dimethylamin und Natriumhydroxid können Thiole, Disulfide, Thiosäuren und thiosaure Ester, desulfurierbare Schwefelverbindungen und Pseudothiole unterschieden werden. Die Empfindlichkeit beträgt 0,1–1,0 pig S/cm². Ergänzende Untersuchung der Flecke mit Formaldehyd bzw. Tetraacetoxyquecksilberfluorescein erlaubt noch die Erkennung von Aminothiolen und Ergothionein sowie einigen Stickstoffverbindungen wie Harnsäure, Tryptophan und Histidin. Die elektrophoretische Trennung wurde bei 50 V/cm, pH 1,7 und 7,4, in 10% v/v-igen Äthylenglykollösungen ausgeführt.Herrn Professor Dr. phil. Alfons Schöberl, Direktor des Chemischen Instituts der Tierärztlichen Hochschule Hannover, spreche ich für wertvolle Anregungen und liebenswürdige Zusendung von zahlreichen Reagentien meinen verbindlichsten Dank aus.     

Eine neue Methode zur Darstellung primärer Phosphine

Zusammenfassung Phosphorwasserstoff bildet mit freiem Aluminiumchlorid einen 1:1-Komplex der Zusammensetzung PH₃·AlCl₃, welcher bei der Umsetzung mit Alkylhalogeniden überwiegend Monosubstitution am Phosphor zeigt. Auf dieser Beobachtung aufbauend, wurde eine Methode zur Darstellung von primären Alkylphosphinen ausgearbeitet, welche die Herstellung dieser Verbindung in günstigerer Weise als die bisher bekannten Synthesenmethoden ermöglicht. Eine Reihe von Alkylphosphinen, darunter zahlreiche bisher unbekannte, wurden hergestellt und über deren Kennzahlen berichtet.Zum 60. Geburtstage von Herrn Prof. Dr.O. Kratky.Auszug aus der DissertationE. Steininger, Techn. Hochschule Wien, 1959; Canad. Pat 618 333 (1961), Franz. Pat. 1 269 142 (1961); 1. bzw. 2. vorhergehende Mitt.: Mh. Chem.90, 148, 792 (1960).     

Muon transfer from protium to helium

Muon transfer from hydrogen isotopes to helium is of importance in muon-catalyzed fusion and serves as a unique tool for the direct observation of the mesomolecular ion (pµHe)^*. During two data-taking runs in 1994 and 1995 at PSI, measurements of the transfer from protium to helium were carried out using CCD's and Ge-diodes as independent X-ray detectors to obtain information on the time distribution and intensity of the 7 keV decay X-ray of the mesomolecular ion. Dual¹H₂ +⁴ He and triple¹H₂ + Ne +^3,4He gas mixtures at low temperatures were investigated to extract transfer rates. Protium of high purity was available. For the first time a transfer rate from muonic protium to³He was measured. A general survey of our measurements and preliminary analysis is presented.     

The influence of electron-phonon scattering on the spatio-temporal dynamics of electronic wavepackets in semiconductor quantum wells

The dynamic evolution of spatially inhomogeneous electronic excitations coupled to a phonon reservoir is investigated on ultrashort time scales. For this purpose, the in-plane propagation of an optically excited electron-hole density profile is studied in an idealized semiconductor quantum well with equal electron and hole masses. Assuming low density and excitation pulses localized on a micron scale, it is shown that the optically induced electron transport exhibits a crossover from ballistic to diffusive motion depending on the details of the electron-phonon coupling.     

Towards quantification of butadiene content in styrene-butadiene block copolymers and their blends with general purpose polystyrene (GPPS) and the relation between mechanical properties and NMR relaxation times

The properties of styrene-butadiene-styrene (SBS) block copolymers do not only depend on the butadiene content and the degree of polymerisation but also on their chain architecture. In this contribution we present the results of a low-field time domain (TD) NMR study in which the transverse relaxation behaviour of different SBS block copolymers was analysed and correlated with findings from mechanical testing on pure and blended materials and transmission electron microscopy data which provide information on the microphase separation.The results indicate that while a straightforward determination of the butadiene content as in blended materials like ABS is not possible for these materials, the TD-NMR results correlate quite well with the mechanical performance of blends from SBS block copolymers with general purpose polystyrene (GPPS), i.e. industrial grade homopolymer polystyrene. Temperature-dependent experiments on pure and blended materials revealed a slight reduction in the softening temperature of the GPPS fraction in the blends.     

Intermediate temperature proton conductors for PEM fuel cells based on phosphonic acid as protogenic group: a progress report

The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with phosphonic acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the phosphonic acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the "spacer concept", which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of phosphonic acid functionalized polymers. Instead, a very high concentration of phosphonic acid functional groups forming "bulky" hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in phosphonic acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl phosphonic acid) and poly(meta-phenylene phosphonic acid) are discussed. Though both polymers exhibit a substantial concentration of phosphonic acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below sigma = 10(-3) S cm(-1) at T = 150 degrees C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat phosphonic acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for phosphonic acid functionalized ionomers (IEC >10 meq g(-1)) may allow for high proton conductivities in the intermediate temperature range (T approximately 120 -160 degrees C).