Photochemische reaktionen—XXXIII: Molekular- und kristallstruktur eines photoprodukts aus gibberelun C

In connection with studies concerning the photochemistry of carbonyl gibberellins, the structure of a ring D seco photoproduct 1 obtained upon UV irradiation of gibberellin C has been established by X-ray analysis and the molecular packing determined. The lattice parameters are a=b=11.935 Å and c=31.717 Å; the space group is P4₃2₁2. The final discrepancy factor R was 0.063.     

Optical conductivity and electron interaction in the one-dimensional metal K2Pt (CN)4 Br0.3 · 3H2O

Experimental and theoretical investigations of the optical conductivity of K₂Pt (CN)₄Br_0,3 · 3H₂O single crystals for phonon energies near the plasma edge are reported. The imaginary part of the dielectric function is determined by only two scattering processes: Elastic scattering of holes by the Coulomb potentials of randomly distributed Br-ions and inelastic scattering by excitation of plasmons.     

Subhalides of tellurium: Electrical conductivity in relation to crystal structure

Subhalides of Te are compounds of the type Te_yX with y ?1 and X = Cl, Br, I. Within this group of compounds the structural building unit of elemental tellurium - the Te-screw with 3₁ or 3₂ symmetry - is continuously modified and yields a series of crystal structures from one-dimensional Te-Te arrangements to a zero-dimensional type. We show qualitatively how the electrical conductivity of these compounds is correlated to the various crystal structures. Gap energies are determined from the temperature dependence of the electrical conductivity.     

Koordinationszahl und nephelauxetischer Effekt von Komplexen der Lanthaniden

The Eu^IIIEDTA complex exhibits a strong temperature dependence of its absorption band at 395 nm in dilute aqueous solution. Similar but much weaker effects can be observed in solutions of SmEDTA and GdEDTA, whereas EDTA complexes of the other lanthanide ions as well as the aquo ions of the whole series show no significant change of their absorption spectra in nation number along the series of the lanthanide EDTA complexes that takes place from Sm to Tb at room temperature. It can be concluded from the nephelauxetic effect that the coordination number decreases with increasing atomic number. The coordination numbers of the aquo ions are the same for all trivalent lanthanide ions in dilute solutions.     

Stationary phases for gas chromatography; chemical stability of polysiloxanes

A number of polysiloxanes have been shown to be sensitive to acids when dissolved in chloroform. At 26O°C polysiloxanes were found to degrade under the influence of several compounds used or produced during the preparation of glass capillary columns.     

Trennung von Elementen durch Extraktion mit leichtschmelzenden organischen Stoffen

Ohne Zusammenfassung     

Trennung des Kupfers, Nickels, Eisens und Bleis von Platin, Palladium, Rhodium und Iridium

Ohne Zusammenfassung     

HPLC-Bestimmung von Blei und Cadmium nach Chelatextraktion mit Na-Diethyldithiocarbaminat

Ohne Zusammenfassung

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Detection of lead and cadmium by HPLC after chelate extraction with Na-diethyldithiocarbamate

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Die Autoren bedanken sich für die Förderung dieser Arbeit aus Mitteln der Deutschen Forschungsgemeinschaft.     

Frequency dependent magnetic susceptibility and spin glass freezing inPtMn alloys

We report measurements of the low-field complex magnetic susceptibility on Pt_1?x Mn _x forx=0.01, 0.025 and 0.05 and for frequencies ν between 10 and 4,000 Hz. A strong frequency dependence of the freezing temperatureT _f is observed: ΔT _f /T _f Δ lnv=0.025 (decade ν)^?1 for all three alloys. These results as well as previous other measurements are interpreted in terms of a phenomenological model.