Kälteadaptation der Wachssynthese in der Harder'schen Drüse der Ratte

Adaptation to Coldness in the Synthesis of Wax Esters in the Harderian Gland of the Rat The Harderian gland of the rat has been shown to contain characteristic wax esters of [n-7] unsaturated alcohols and fatty acids. The change of the temperature in the surroundings from 25 to 4° C for six weeks does not change the pattern of exclusively [n-7] monoenoic fatty acids. The adaptation of this exocrine eye gland results in an increased synthesis of [n-5] monounsaturated alcohols and shortening of the chain length. Different pathways of unsaturation and/or chain modification and the regulation of lipid synthesis in this gland are discussed, as well as the biological role of these waxes.     

Vergleich der Verteilungskurven der Katalysatorkorngrößen bei der Hydrierung von Fetten

Comparison of the Distribution Curves of the Particle Sizes of Catalysts in the Hydrogenation of Fats In the present paper the particle sizes of 14 hydrogenation catalysts and 2 kinds of commercial kieselguhr were studied using a laser analyzer. Assuming a log-normal distribution the distribution curves for the particle sizes were treated by the least-squares method. From the μ and σ parameters obtained the different characteristics of the catalysts were discussed.     

Der einfluß der luftfeuchte bei der verfärbung von PVC während der bewitterung und bei der anschließenden dunkellagerung

The influence of humidity on the light-fastness and the dark time yellowing of white PVC and special changes of the irradiated surfaces are described. The results show, that the boundary surface climate at the irradiated specimen surfaces has a decisive influence on the ageing results.     

Schätzung der Investitionskosten bei der Prozeßentwicklung

Estimation of Investment Costs in Process Development. This article gives an overview of plant cost estimating; the corresponding data and authors who have described the individual methods can be obtained from the primary literature. The definitions, the present authors, own data and experience gained in Germany, the pros and cons in practice of each cost estimating method are presented. The turnover ratios, capacity ratio exponents, step-counting methods, and factor methods are emphasized for cost estimating in a situation of comparative uncertainty in the early stages of a project, because unit cost methods and detailed cost estimating are often used for budgeting.     

Über die elektrochemische methode der bestimmung der depolarisationsfähigkeit der aktivkohle

The method described consists in the discharge of a cell with the system C/active carbon/electrolyte/Zn. The method allows the determination of the influence of wetting, of pressure and of various additives such as graphite. The electrolyte content (humidification) has a great influence on the depolarization capacity. With seven types of active carbon, there is an optimum value of humidification at which the carbon has the highest depolarizing capacity; this optimum lies between 15 and 41 per cent.

Increase of pressure causes a decrease of depolarizing capacity.

Addition of carbon black has a favourable influence on the depolarizing capacity. This is especially marked with certain types of active carbon. Graphite decreases the depolarizing capacity, but the effect is small.     

Abhängigkeit der UV-Absorption binärer Styrol-Copolymerisate von der Länge der Styrolsequenzen

The UV-spectrometer is proposed in the literature as a second detector for gel permeation chromatography, independent of the usual differential refractometer. The intention is to get information on the variation of the chemical composition of styrene copolymers with molecular weight. The present paper disproves the usual assumption that UV-absorption of styrene copolymers is depending only on the concentration of phenyl rings. However, the absorption also depends on the length of the styrene sequences and therefore mostly on the monomer ratio in the copolymer. The UV-spectra of binary styrene copolymers with ecrylonitrile, maleic anhydride and butadiene were measured at different monomer ratios. From the measurements we calculated the molar absorption coefficient of the phenyl ring for different absorption bands. In comparison with homopolystyrene it is shown that both the position and the absorption coefficient of the bands can depend on the sequence length distribution of the copolymers. We suggest this to be caused by dispersion interactions between neighbouring phenyl rings. Consequences for the use of a UV-spectrometer as a detector for gel permeation chromatography are discussed.     

Stand der Emissionsmeßtechnik im Abgas der Rückstandsverbrennung

State of the art of emission measuring techniques in the flue gas of waste incineration plants. It is necessary to critically consider measuring techniques in the light of new requirements for waste incinerators (17th ordinance dating from Dec. 1990). Selected examples are concerned with the primary components of flue gas: particulate matter and trace metals, organics with total carbon content, and important groups such as organochlorine compounds (e.g. dioxins/furans) and inorganic chlorides (such as hydrogen chlorine). The evaluation concludes by considering manual techniques as well as monitoring systems and measures for quality assurance. Finally, an account of recent developments in the monitoring of ammonia and mercury is presented.     

Einige fragen der tunneltheorie der wasserstoffüberspannung—II. Die temperaturabhängigkeit der stromdichte und die beträge der quanteneffekte

The dimensions of the potential barrier involved in hydrogen and deuterium evolution on mercury are computed from the experimental values of the effective activation energies on the assumption that the barrier has a parabolic shape. The ratio of the pre-exponential factors and the isotopic separation factor obtained theoretically in this manner are in good agreement with experimental data. The calculation shows that the tunnel effect plays a substantial but still moderate role in the case under study. Comparison with the results of an earlier derivation based on Eckart's potential function allows the determination of the most probable shape of the true barrier. The usually assumed dimensions are shown to be incorrect.

Résumé

On calcule les dimensions de la barrière de potentiel pour le dégagement d'hydrogène et de deutérium sur le mercure en partant des valeurs expérimentales de l'énergie d'activation et en supposant que la barrière a une forme parabolique. Le rapport des facteurs préexponentiels et le facteur de séparation isotopique ainsi obtenus théoriquement sont en accord avec les données expérimentales. Le calcul montre que l'effet tunnel ne peut être négligé mais qu'il ne joue cependant qu'un rôle moyen dans le cas étudié. La comparaison avec les résultats d'une dérivation précédente partant de la fonction de potentiel d'Eckart permet de déterminer la forme la plus probable de la barrière de potentiel. Il est montré que les valeurs habituellement admises pour les dimensions de cette barrière ne sont pas correctes.     

Einfluß der Diffusion auf die Selektivität der Schleppmittel-Destillation

Influence of diffusion on the selectivity of entrainer distillation . The selectivity of azeotropic distillation generally depends not only on the relative volatility but also upon the rate of diffusion of the participating components in the liquid and the gaseous phase. If the less volatile material diffuses faster in the gas phase than the more volatile material, then the former can also accumulate in the gas phase. In such a case the azeotropic points do not necessarily represent separation limits. This effect might also be utilized in the separation of azeotropic mixtures in specific cases. On the other hand, a large diffusion resistance in the liquid phase can override any selectivity. An estimate shows that selective drying of porous materials containing binary solvent mixtures is therefore practically impossible. Azeotropic distillation is also suitable for investigating column plates and packings with the aim of isolating the hydraulic and kinetic reasons for the imperfect equilibration always observed. These questions, overcoming azeotropic points, non-selective drying, and the reasons for imperfect equilibration in separation columns, are discussed in the light of theoretical results and experimental data obtained for practical azeotropic distillations.     

Anwendungsmöglichkeiten der homogenen Übergangsmetallkatalyse in der Fettchemie

Homogeneous Transition Metal Catalysis in Oleochemistry Numerous processes in industrial oleochemistry are carried out using transition metal catalysts. However, in most cases the catalysts applied are heterogeneous. The present review considers the huge number of possible applications of homogeneous transition metal catalysis in oleochemistry. The advantages of homogeneous transition metal catalysis are the high selectivity and the mild reaction conditions. These advantages are often used in petrochemistry, but in industrial oleochemistry exist no similar developments. The results of the laboratory research in the last two decades prove that the special properties of homogeneous transition metal catalysts can be applied in oleochemistry too. Well known chemical reactions could be improved and new reactions could be developed. The present review refers some of the most interesting reaction types, e. g. the selective hydrogenation of manifold unsaturated fatty acids or the possibilities to isomerize the double bonds selectively. Oxidation reactions, reactions with carbon monoxide, metathesis, CC-linkage reactions, telomerizations and additions to the double bonds of unsaturated fatty compounds will also be presented.