Über den Einfluß von einwertigen Zwischenschichtkationen auf die elektrische Leitfähigkeit von Vermikulilten in verschiedenen Hydrationszuständen (Dielektrische Messungen an Schichtsilicaten IV (1, 2, 3))

Zusammenfassung An Vermikulitkristallen mit Li⁺ und Na⁺ als Zwischenschichtkationen in verschiedenen Hydrations-zuständen (trocken, isolierte Wassermoleküle und monomolekulare Wasserschichten) wurde der Realteil der dielektrischen Permeabilitätg und der dielektrische Verlustfaktortg im Frequenzbereich zwischen 30 Hz und 10 MHz gemessen. Die elektrische Leitfähigkeit in Richtung der Schichtnormalen wird sowohl vom Hydratwasser als auch (insbesondere bei niedriger Schichtladung) von der Natur der einwertigen Zwischenschichtkationen bestimmt: Bei niederen Frequenzen und niederen Hydrationszuständen dominieren Relaxationsphänomene auf Grund der Beweglichkeit dieser Kationen. Hingegen resultiert die Leitfähigkeit in den Stufen mit isolierten Wassermolekülen und mit monomolekularen H₂O-Schichten weitgehend aus einem Wanderungsmechanismus vonL-Defekten innerhalb der Wasserstrukturen, wie er bei Vermikuliten mit zweiwertigen Kationen nachgewiesen wurde.

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Summary The dielectric permeability s' and the dielectric losstg of vermiculite crystals with Li⁺ and Na⁺ as interlayer cations in different states of hydration (completely dehydrated, with isolated water molecules and with monomolecular water layers) were measured in the frequency range between 30 Hz and 10 MHz. The electrical conductivity normal to the silicate layers was determined by the influence of the hydrate water as well as especially in the case o£ low layer charge by the nature of the monovalent interlayer cations. At low frequencies and low states of hydration it could be interpreted by a relaxation process of the interlayer cations. With isolated water molecules and with monomolecular water layers the conductivity at higher frequencies was mainly determined by a mechanism of diffusion of structuralL-defects within the water layers as in the case of hydrated vermiculites with divalent cations.

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Mit 9 Abbildungen und 2 Tabellen     

A theoretical study of the electromagnetic properties of ferrocene and the ferrocenium ion

An iterative extended Hückel molecular orbital calculation was used to obtain wave functions for the ground state of ferrocene and several low lying states of the ferrocenium ion. Photoemission spectra in terms of relative ionization potentials and the electric field gradient at the iron nucleus were calculated for ferrocene andg values and the electric field gradient were calculated for the ferrocenium ion. These values are in good agreement with experiment. The nature of the molecular orbitals was compared with results of previous semi-empirical andab initio calculations.     

Sila-Analoga des Chlorphenoxamins und des Clofenetamins

Sila-analoguesA 2 andB 2 of two drugs from the benzhydryl ether class, chlorphenoxamine and clofenetamine, were synthesized for the first time by the steps shown in scheme 1. They and their precursors I–VI were characterized by their physical (Table 1) and chemical properties and their structures confirmed by n.m.r., mass and infrared spectrocopy (Tables 2–5). Their physiological effects were investigated and compared with those of the carbon analogues (Chapter 5).

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1. Mitt.:R. Tacke undU. Wannagat, Mh. Chem.106, 1005 (1975).

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Mit Auszügen aus der DissertationR. Tacke, Techn. Univ. Braunschweig 1974.     

Über die Anwendung der Kohlepaste-Elektrode zur inversvoltammetrischen Bestimmung kleiner Quecksilbermengen

The applicability of the carbon paste electrode to the determination of trace quantities of mercury has been investigated in a base electrolyte of 0.1 N KSCN + 0.025 N HCl containing 25 ng/ml copper. The detection limit of the mercury determination has a value near 2.5 ng/ml (1.25×10^?8 M), if pre-electrolysis is carried out 10 min at ?1.0 V and the current voltage curve is registered with a scan rate of 16.7 mV/sec between ?0.5 and +0.5 V. The peak height is directly proportional to the concentration in the range from 1.25×10^?8 to 1.25×10^?6 M. With appropriate preconditioning the carbon paste electrode can be used for several measurements without renewing the surface.     

Spectres de Masse de Derives de l'Atractyloside. Determination du Nombre de Substituants par Combinaison d'Acetylation et de Silylation

Different transformations of the functions fixed on a heterocyclic molecule were made. It is thus possible to quickly determine the number of functions of each type present in the molecule: e.g. (i) all the functions are silylated and (ii) the alcohols are acetylated whilst the sulfates and acids are silylated. Mass spectra of atractylate, apoatractylate and gummiferine have been studied and the substituents are counted and enumerated.