Role of P2O5 in TiO2-Opacified Porcelain Enamels

Phosphorus pentoxide is known to affect the reflectance and color of TiO₂-opacified porcelain enamels. It has been postulated that P₂O₅, impedes the anatase-to-rutile phase transformation. This hypothesis was tested by applying recently developed analytical procedures based on X-ray diffraction analysis to a typical porcelain enamel cover coat system. The inversion of anatase to rutile was not significantly affected by P₂O₅. Instead, in the range 0.5 to 4%, as P₂O₅ concentration was increased in the frit, the rate of crystallization of both anatase and rutile also increased, with the rate of increase of anatase being about twice that of rutile.     

Exploring single electrode reactions in polymer electrolyte fuel cells

Utilising a pseudo-reference electrode in polymer electrolyte fuel cells allows for the separation of anodic and cathodic contributions to the entire cell impedance. Modelling the impedance responses by using equivalent circuits inhibits the investigation of kinetic parameters of the basic electrochemical reactions, which take place at single electrode-electrolyte interfaces. Therefore, we evaluate single electrode impedance measurements by a kinetic model, which is based on specific reaction pathways, either for the oxygen reduction reaction (ORR) or the hydrogen oxidation reaction (HOR). As a consequence, it is possible to obtain kinetic parameters for the specific reaction of interest. Furthermore, the information gained from the single electrode impedance measurements and the kinetic model can give insight into single reactions steps. In particular, the ORR has to include a chemical step in the reaction pathway.     

Facile preparation of amphiphilic oxyethylene-oxypropylene block copolymers by selective triazine coupling

A novel synthetic route for preparing high molecular weight poly(oxyalkylene) block copolymers has been developed by using 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride, cc) as the coupling core. The coupling reaction involves the selective substitutions of oligo(oxyalkylene)-amines onto three chlorides of the triazine ring in a stepwise manner at 0, 25 and 130 °C. By judiciously selecting the starting amines and reaction conditions, one can tailor the copolymer structures with different block configurations (tri-block, multi-block, random and alternating block). The prepared copolymers can have a high molecular weight, up to 25,600 g/mol (GPC polydispersity=1.48), and also high thermal stability due to the presence of triazine functionalities. The copolymers with hydrophilic and hydrophobic oligo(oxyalkylene) blocks are of versatile properties in solubility (water soluble or water insoluble) and morphology (crystalline or amorphous). With a specific structure of alternating oligo(oxyethylene)/oligo(oxypropylene) blocks (2000 g/mol each block), the copolymer exhibits the property of self-association. It reduces the interfacial tension of toluene/water as low as 0.5 dyne/cm at the critical micelle concentration of 0.01 wt%.     

Über die Herstellung von α-Sulfofettsäureestern

Preparation of Esters of α-Sulfo-Fatty Acids A process for the continuous α-sulfonation of saturated fatty acid esters with SO₃ was worked out and a special bleaching process was developed for these products. The conversion, i. e. the degree of sulfonation is of the order of 95–99%. Solvents, further processing steps or purification operations for the separation of by-products are not required.     

Kinetic investigations in heterogeneous reaction systems by wavefront analysis

In this paper the previously introduced wavefront analysis is extended to heterogeneous reaction systems, which consist of several reaction steps. It is shown how three mainly informations obtained at the wavefront, namely the damping of the wavefront, the time-gradients at the wavefront and the propagation velocity of the wavefront, can be used for kinetic investigations of a reaction step under consideration.     

Ertragsleistung sowie Gehalte und Zusammensetzung der Fette und Proteine einiger Senfarten und -sorten auf ökologisch stark differenzierten Standorten

Yield as well as Contents and Composition of Fats and Proteins in Several Varieties and Types of Mustard at Distinctly Different Ecological Locations In a cultivation experiment extending over two years the yield of different varieties of Brassica juncea, Brassica nigra and Sinapis alba was examined. Fat content and protein content were determined and the correlations with different characteristics were calculated. Fatty acid composition of the oil showed that erucic acid content was distinctly influenced by the location and the year of cultivation. In all samples, whose erucic acid content showed large difference from average values for the variety, electrophoretic patterns of the proteins were found to be distinctly different, both with respect to number and distribution of the bands.     

Ion exchange kinetics of the protonation of weak acid ion exchange resins

A mathematical model to describe the protonation of weak acid ion-exchange resins with various acids has been developed. The charge profiles calculated using the theory are demonstrated by photographs. Interdiffusion coefficients in the resin phase have been determined and it is shown how they depend on the system parameters and on the properties of the resin.     

Über den Effekt der Einarbeitung von Diolen in Alkydharze auf Basis verzweigter Carbonsäuren

The Effect of the Use of Dihydric Alcohols in the Alkyd Resins Based on Branched Chain Fatty Acids By the modification of alkyd resins, based on the branched chain fatty acids with dihydric alcohols, the properties of the resins are strongly influenced. Not only the length but also the structure of the chain between two hydroxyl groups of the dihydroxy alcohol exert a considerable influence on the mechanical properties of the lacquer film. In addition, the structure of this chain is also important for the chemical resistance. The influence of the dihydroxy alcohol on the mechanical properties of the hardened lacquer films is partly due to the greater flexibility of the cross-linked system and partly due to the better plasticizing effect of the unbound alkyd part.     

The Systems BaO-SrO-TiO2, BaO-CaO-TiO2, and SrO-CaO-TiO2

The solid phases formed at 1400°C. in air in the three-component systems BaO-SrO-TiO₂, BaO-CaO-TiO₂, and SrO-CaO-TiO₂ are described. Besides solid solutions of components with known structures, some new ternary compounds have been studied. The dielectric constants and loss factors of a number of specimens are given. Crystallographic data of the compounds BaCaTiO₄, Ba₃Ca₂Ti₂O₉, and Ca₃Ti₂O₇ and of the solid solution series (Ba, Sr), TiO₄ are presented. The preparation of the new compounds is described in detail.