Elektrochemisches Rauschen von Magnesium in organischen Lösungsmitteln

Electrochemical Noise of Magnesium in Organic Solvents The electrochemical noise of the system Mg/n-C₄H₉OH, NaClO₄ is analyzed on different conditions. The suitability of this method is to be investigated for the determination of selfdischarge of galvanic cells. Gravimetric measurements, radiometric methods and visual judgement of anode surfaces are taken for this hitherto. The long-term stability of the system without polarization up to 75 days is confirmed by constant noise amplitude and comparative EIS-measurements. The system activated by constant polarization showed a corrosive attack indicated by an increasing current noise amplitude within some hours. Finally passivation occurred after advanced destruction of the oxidic surface layer. The noise amplitude diminished. Salt deposit caused this event, corroborated by SEM shottings. Analysis of potential noise in nonaqueous electrolytes is inconclusive owing to inherent noise of used reference electrodes of 2. kind.     

Benzophenon-photoinduzierte Oxydationen von Benzylarylethern und aromatischen Lösungsmitteln

Benzophenone Photoinduced Oxidation of Benzyl Aryl Ether and Aromatic Solvents α-Ether radicals formed in the photoreaction of benzophenone with benzyl phenyl ether were oxidized in benzene solution to phenol, benzaldehyde and phenylbenzoate. A mechanism including an instable intermediate α-ether hydroperoxide is discussed with the help of kinetic and CIDNP results. The quantum yields of the oxygen consumption show a linear dependence on the ether concentration. They are much higher in the pure solvent benzene than expected from the quenching and deactivation processes. This agrees with the existence of a biradicalic adduct of triplet benzophenone with aromatic solvents and shows that these solvents are far from being inert under these conditions.     

Über die Bestimmung des Wassersolubilisiervermögens von Tensiden in organischen Lösungsmitteln

Determination of Water Solubilization Capacity of Surfactants in Solvents The water solubilization capacity, i. e. the maximum amount of water which can be dissolved in micellar form in a given amount of solvent by a given amount of surfactant, resp. dry-cleaning detergent, was determined according to two different methods. As a model system, the system water-perchloroethylene-Na-dioctylsulfosuccinate wes chosen, at temperatures of 15°C, 25°C and 35°C. The method according to DIN 53980 (draft) is satisfactory, but its field of application and the information it yields are restricted. An improved titration method was developed. It could be used without difficulty even at high concentrations and temperatures.     

Viskosimetrische Untersuchungen an Styrol-Acrylsäure-Copolymeren und deren Alkalisalzen in organischen Lösungsmitteln

The viscosity and conductivity of a styrene-acrylic acid copolymer containing 8.7 weight-% acrylic acid and of its Li-, K- and Cs-salts were studied in tetrahydrofuran and in a mixed solvent containing THF and methanol (volume ratio = 4/1). The change of the specific viscosities η_rel – 1 by variation of the neutralization degree, of the concentrations of the solutions and of the type of solvent was pursued. By increasing the neutralization degree solutions with concentrations > 2.5% were found to pass maxima of specific viscosity. Using THF as solvent at concentrations below 1% a decrease of the (η_rel – 1)-values takes place. The viscosity-number [η] decreases with increasing neutralization. In the mixed solvent (THF/CH₃OH = 4/1) the K- and Cs-salts are passing a minimum of viscosity at medium degrees of neutralization.     

Rückgewinnung von Lösungsmitteln aus der Abluft

Recovery of Solvents from the Vent Air The economic, safety and hygienic aspects of the recovery of solvents from the vent air of plants that handle solvents are dealt with. Physical laws that enable the quantitative determination of solvent content of vent air are discussed. In an example, the amount of vent air in a solvent extraction plant and its solvent content have been determined. The physical and technical scopes for the recovery of solvent from vent air are outlined and the various system are compared with special reference to the absorption technique.     

Desaktivierungsverhalten von Arenen und Heteroarenen. XXXIII. Zur statischen Löschung der Fluoreszenz von Azinium-Anthracenen in Lösungsmitteln mit n-Donatoreigenschaften

Deactivation Behaviour of Arenes and Heteroarenes. XXXIII. Static Fluorescence Quenching of Azinium-Anthracenes by Solvents of n-Donor Properties The fluorescence of azinium-anthracenes is quenched by solvents of n-donor properties. A model of static quenching by electron transfer is developed analogous to the dynamic process. The rates of quenching correlate with the donor properties of the solvent (ionization potential) and the acceptor properties of the fluorophor (reduction potential). In the same way as in the case of dynamic quenching this static process is characterized by a high free enthalpy of activation. The existence of a thermally induced step in the process of the electron transfer affects the temperature dependence of the fluorescence quantum yields. The analysis of this temperature dependence on the basis of an Arrhenius equation shows a linear relationship.     

Verfahren zur Bestimmung des Lösevermögens bzw. die Lösekraft von Lösungsmitteln für Öle und Fette

Procedure for the Determination of Dissolving Property and Dissolving Power of Solvents for Oils and Fats A “circular filter paper chromatographic procedure” for the quantitative determination of dissolving ability and dissolving power of cleaning agents is described. From the ratio of the rate of migration of the solvent to that of the solution and a correction factor for the area, the criterium for the above determination is calculated. A paper-chromatographic filter serves as the stationary phase, and as mobile phase is taken a solution comprising of a fat or oil and the solvent to be examined. By this means, a satisfactory separation can be achieved between unused solvent, solvent saturated with fat or oil, and undissolved fat or oil. These three phases occur in a state of equilibrium on the paper chromatogram. This procedure is applicable to all fats and oils which are visible under UV light.     

Destillative Rückgewinnung von mit Feststoffen verunreinigten Lösungsmitteln

Recovery of Solvents from Solid Containing Mixtures by Distillation In the chemical industry solvents contaminated with solids are often formed when cleaning the machinery. During recovery difficulties frequently arise because the heating surface is strongly incrusted due to the residue. Referring to a plant which is running since 1965 nearly free of maintenance the process is described including problems caused by the nonvolatile contents. The unusable rest is obtained as a compact sludge. If the residue is free from volatile chlorocarbon compounds special dumps may be used.     

Einfluß von Lösungsmitteln auf den Partikeldurchmesser von Dispersionen anionischer Polyurethanionomerer

Aqueous dispersions of anionic polyurethanes were prepared by reaction of polyethers, 1,6-hexamethylene diisocyanate, 1,2,4-benzenetricarboxylic acid anhydride and triethyl amine. Formation of the dispersion was achieved by phase reversal or by precipitation. Phase reversal occurred when the solution or the melt of the polymer was treated with water, while precipitation took place when the solution was stirred into water. The amount of acetone used has an effect on the mean particle diameter, D?_T, obtained by turbidity measurements. There was an optimal acetone concentration at which D?_T reached a minimum. A similar effect was observed when tetrahydrofuran, 2-butanone or acetonitrile were used as solvents instead of acetone. When the dispersion was formed by precipitation, only adequately diluted acetonic solutions formed colloidal dispersions, while concentrated solutions gave dispersions with a broad particle size distribution.     

Keramische Membran zur Wasserabtrennung aus Lösungsmitteln

Novel hydrophilic SiO_x modified alumina membranes with high separation factors and flux rates have been prepared for the separation of water from organic solvents. The membranes are prepared by the deposition of SiO_x networks inside the γ‐Al₂O₃ layer of a commercial ultrafiltration membrane by hydrolysis of tetraethylorthosilicate in autoclaves at 250°C. The transport resistance of the individual membrane layers to the permeation flux are described by a model. The membranes are stable towards solvents up to at least 150°C. Pervaporation studies show that water can be separated from solvents like acetonitrile, tetrahydrofuran, 2‐isopropanol, ethanol, dimethylsulfoxide, dimethylformamide, phenol. The separation performance of the membranes allows their use in technical separation processes, especially for the remove of water.