Über analytische Untersuchungen an magnetischen Materialien

The determination of Co, Ni, Cu, Si, Mn, Cr, Ca, Na and K in cubic ferrites and their starting materials by colorimetric and flame-photometric analysis is described. The separation of the trace elements is often possible by extraction. The relative error is about 10 to 20%.     

Gleichgewichtsdruckmessungen im System Se/O/Br

Equilibrium Pressure Measurements in the System Se/O/Br The saturation pressure or saturation decomposition pressure of SeOBr_2,l, Se₂Br_2,l and SeBr_4,s were determined in a membran zero manometer. The decomposition behaviour follows from pressure measurements outside of saturation. From the equilibrium data are derived the Enthalpies of formation: Data see Inhaltsübersicht. Informations about the melting diagrams obtained via the barograms of the condensed compositions SeO₂/SeBr₄ and Se/Br.     

X-ray standing wave fluorescence measurements in ultra-high vacuum: Adsorption of Br on Si(111)−(1×1)

Measurements with standing X-ray wave-fields were carried out for the first time under UHV conditions. Difficulties which were predicted for such measurements before were solved by using synchrotron X-radiation. The (111) Fourier component of the distribution function of 1 ML Br on a Si(111)?(1×1) surface was determined and reveals a Br position of 0.64 · d₁₁₁ perpendicular to the (111) planes, which favours a three-fold ionic adsorption site. This adsorbate geometry differs markedly from the Br on-top position on a chemically prepared surface.     

Solution enthalpies of hydrates LnCl3·xH2O (Ln=Ce–Lu)

Trichlorides of the lanthanide elements Ln=Ce–Lu form: (a) isotypic hexahydrates LnCl₃·6H₂O with a coordination number (CN) 8 for the Ln³⁺ ions. (b) Two isotypic groups of trihydrates LnCl₃·3H₂O, in the first group Ln=Ce-Dy the CN is 8; the structure of the second group Ln=Er–Lu is unknown. With Ho no trihydrate exists; a dihydrate is formed. (c) Two isotypic groups of monohydrates LnCl₃·H₂O with unknown structure – Ln=Ce–Dy and Ln=Ho–Lu. For all compounds and for anhydrous chlorides LnCl₃ solution enthalpies were measured with an isoperibolic calorimeter. The Δ_solH⁰ values do not depend only on the difference (lattice enthalpies/hydration enthalpies), but also on the state in solution. According to Spedding the CN of the Ln³⁺ ions against water changes from 9 to 8 between Nd and Sm, causing minima in the series of solution enthalpies. Dihydrates LnCl₃·2H₂O are found for Ln=Ce, Pr, Nd, Sm and presumably for Eu and Gd. They are not yet well characterised.     

Zur Berechnung der Matrixelemente des Dichteoperators für die überlagerung Zweier Elektromagnetischer Felder

A method for calculation matrix-elements of the density operator for the superposition of two electromagnetic fields from the matrix-elements of the two components is developed. In the special case of superposition of a stationary coherent field and a stationary chaotic field results are compared with Peina's results.     

An efficient three-step synthesis of cyclopenta[b]pyrans via 2-donor-substituted fischer ethenylcarbenechromium complexes

A wide range of cyclopenta[b]pyrans 4 has been synthesized in a one-pot reaction by treatment of different 2-donorsubstituted ethenylcarbenechromium complexes 2 with alkynes in THF in moderate to excellent yields (41-90 % for 14 out of 25 examples). The starting materials 2 are readily available in good to excellent yields (76-99 % for 25 out of 36 examples) by Michael addition of amines, alcohols and thiols, respectively, to the corresponding alkynylcarbenechromium complexes 1. Due to their 10 pi-electrons in a cross-conjugated bicyclic system, cyclopenta[b]pyrans have been termed pseudoazulenes, as they indeed have similar UV/Vis-spectroscopic properties.