Über wäßrige Dispersionen von Polyoxymethylenen

Polyoxymethylenes with hydrophilic groups or hydrophilic polymer sequences incorporated are dispersable in water. Especially copolymers of trioxane with free carboxylic groups can be used for this purpose. These copolymers are prepared by saponification of the corresponding estergroups containing polymers. The incorporation of estergroups in polytrioxane is possible by copolymerization, by chain transfer reactions or by grafting reactions. Polyoxymethylenes where the ionic groups are replaced by nonionic hydrophilic polymer sequences are also dispersable in water. To prepare a dispersion the polymers are dissolved under pressure in a low boiling solvent, water and, if needed, a dispersing agent are added and the solvent is evaporated.     

Ionenadsorption an Elektroden in wäßrigen und nichtwäßrigen Elektrolyten

Adsorption of ions on electrodes in aqueous and nonaqueous electrolytes . This article considers the practical implications of adsorption of electrolyte ions on electrodes and methods for quantitative determination of electrosorption of ions. Adsorbed ions influence the potential drop in the inner Helmholtz layer and thereby modify the rate of charge transfer for redox processes occurring at electrodes, and the chemical reactions ensuing upon charge transfer can be effectively directed by adsorbed ions. Corrosion and its inhibition as well as deposition of metal in electroplating can be influenced by surface-active ionic additives which are adsorbed. Measurement of differential capacity provides information about the electrosorption of ions and neutral compounds. A knowledge of the zero point of the electrode metal permits clear predictions concerning ion adsorption. Anions are preferentially adsorbed at potentials on the anodic side of the zero point, and cations at potentials that are more negative than the zero point. Surface-active neutral compounds and lyophobic ions are most strongly adsorbed in a narrow potential range around the zero point. Adsorption of weakly solvated ions on hydrophobic metals (e. g. Au, Hg) is more pronounced than the adsorption of strongly solvated ions on hydrophilic metals (e. g. Ga, Cd, Zn).     

Quellungserscheinungen an wäßrigen Gelatinegelen

The temperature and pH-dependence of the swelling of acid-processed gelatin was investigated. For stabilisation of the samples glyoxal was added as crosslinking agent. Swelling of the samples at different temperatures leads to different crosslinking densities. Degradation of network at temperatures higher than 10°C produces a time dependence of measured values. For the determination of the equilibrium swelling curve an extrapolation method was developed to eliminate the time dependence and to relate the degrees of swelling to constant crosslinking density. The slope of the equilibrium swelling curve shows deswelling of gelatin in water with increasing temperature. Using the equation between the slope of the swelling curve and the differential partial molar enthalpy of the solvent at the swelling maximum derived from the equilibrium condition for the chemical potential of the solvent an exothermic behaviour was found. pH-dependence of swelling corresponds qualitatively with Flory's theory. Hydrolysis in the alkaline region is much stronger than in the acid region. At pH = 12,8 hydrolysis increases sharply.     

Einführung in die Transportvorgänge in konzentrierten wäßrigen Elektrolytlösungen und Salzschmelzen

Introduction to transport phenomena in concentrated aqueous electrolyte solutions and molten salt mixtures . Up to this day there is no general theory of liquids. Since water-free molten salt mixtures are simpler in their structure than concentrated aqueous electrolyte solutions, it would be reasonable first to develop a theory for molten salts and then to apply this to aqueous electrolyte solutions by approximation. Such a theory does not yet exist. In this paper the system water + salt is therefore considered in the concentration range between pure water and pure salt in the liquid state. The phenomenological coefficients and friction coefficients of the different species of the system calculated from transport data are characteristic parameters for the entire concentration range which will probably offer possibilities for the analysis of transport phenomena, in close relation with the structure of the water + salt mixture. Common and essentially different properties, such as reference system and condition of electric neutrality, are discussed for concentrated aqueous electrolyte solutions and molten salt mixtures. The investigation of transport numbers from concentration cells with transference and the determination of the interdiffusion coefficients are illustrated for the system H₂O + CaCl₂ (highly concentrated electrolyte solution) and LiNO₃ + AgNO₃ (molten salt mixture). The phenomenological coefficients and the friction coefficients are calculated from the measured transport data.     

Adsorption von phenolen aus den wäßrigen lösungen an nichtionogenen adsorberharzen

The adsorption and desorption of phenol and p-nitrophenol from aqueous solution on macroporous non-ionic adsorption resins and on active carbon, respectively, has been studied. The reversibility of adsorption on the resins has been observed, in opposition to the nonreversible process found on the active carbon. The adsorption isotherme data measured have been used to the surface area estimation; the method of inflection point and BET-equation have been compared. The practical identity of both methods above has been demonstrated, in the case of straight isotherme curves the BET-equation proved to be useful.     

Fluoreszenzlöschung und Excimerenbildung von Pyren-3-sulfonat in wäßrigen Lösungen von Polydimethyldiallylammoniumchlorid

Quenching of Fluorescence and Excimer Formation of Sodiumpyren-3-sulfonate in Aqueous Solutions of Polydimethyldiallylammonium Chloride The fluorescence spectra and lifetimes of sodium-pyren-3-sulfonate have been measured in the presence of polydimethyldiallylammonium chloride. It is shown, that the excimer formation by static self-quenching of fluorescence of the pyren-3-sulfonate is based on the cooperative effect of the macroion. The association constants of interaction between the aromatic compound and the polycation are determined. Presence of diazoniumcations leads to quenching of fluorescence of pyren-3-sulfonate in both the polyelectrolyte and aqueous phases. The quenching constants are discussed.