Untersuchungen zur Kationenbindung an hydrolytisch abgebauten Cellulosepulvern

Ohne Zusammenfassung     

Zur anwendung der transformations—impedanzspektrometrie

Besides other modern techniques of impedance measurement, such as the automatic digital balance of impedance bridges, or multichannel measurement of impedance components, the frequency dependent impedance of electrochemical systems can be determined by Laplace-transformation of linear perturbation and response functions from the time domain: Laplace-transform—impedance spectrometry. In this paper, some results of our current work on the development of the transform method are treated.Chapter 2 gives a short summary of the theoretical basis of the method, including different variants of evaluation (s-transformation; transformation of impedance components). The main types of perturbation are (a) the (ideal or nonideal) potential step function, (b) the charge injection (current-δ-function). Both types of perturbation are complementary with respect to the decay behaviour of the associated response (Chap. 3).In Chapter 4 possible errors of transformation are discussed in some detail: (a) error of synchronization of perturbation and response; (b) linear distortion of perturbation and response because of limited band width of measuring receivers; (c) breaking off the time integration at a finite time; (d) errors of numerical integration. While the errors (a, b, d) generally increase with increasing frequency, error (c) increases with decreasing frequency. Details of the error characteristics depend on the type of perturbation and on the form of impedance spectrum. Some points of the computer programs for numerical transformation and correction, and of the measuring devices are mentioned shortly in Chapters 5 and 6.In the low frequency limit, true experimental information (without simulated extrapolation) is obtainable up to about the reciprocal measuring time of response function. Of course, the main advantage of transform—impedance spectrometry should lie in the possibility of an extremely fast measurement.Experimental work, including molecule adsorption processes and study of time dependent impedance spectra in mixed adsorption systems, is in progress.     

Two dimensional TLC determination of PAH in diluted automobile exhaust gases

A method is described for the determination of polycyclic aromatic hydrocarbons (PAH) in the diluted exhaust gas of diesel vehicles. Sampling is done by drawing off proportional streams from the dilution tunnel. The particulates deposited on filters are sublimed, and the sublimate is purified and prefractionated on silica gel. Further separation and quantitative determination of the PAH is performed by two dimensional TLC in conjunction with In situ fluorescence spectrometry. Results of theoretical considerations and experimental data on the distribution of the emitted PAH between particulate matter and the corresponding gas phase in diluted exhaust are presented. A modified Langmuir adsorption model is used to explain the effects of dilution ratio and sample temperature in the dilution tunnel. Comparison of the emission values for PAH obtained from diluted and undiluted exhaust shows good agreement. Furthermore, the PAH contents of the exhaust gas of several diesel-engined cars are also compared for various driving cycles.     

Die Abreißenergie von Teilchen aus der fluiden Phasengrenze

Ohne ZusammenfassungMit 1 AbbildungMitt.-Nr.: 317     

Berührungsloses Messen von Oberflächenspannung und prinzipielle Möglichkeiten zum Bestimmen des Randwinkels eines Fluides mit dem Interferenzmikroskop VELOMET-INTERPHAKO des VEB Carl Zeiss Jena

Zusammenfassung Mit Hilfe der InterferenzmikroskopeEPIVAL-Interphako oderVELOMET-Interphako können Oberflächenspannung und Randwinkel einer Flüssigkeit bestimmt werden, indem man die Neigungswinkel des Meniskusprofiles an zwei Punkten im horizontalen Abstand ₁, und ₂ von einer ebenen vertikalen Platte mißt. Die Methode und ihre Genauigkeit werden beschrieben und Testbeispiele für die Oberflächenspannung angegeben.

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Summary The surface tension and contact angle of a liquid can be determined by means of the interference microscopesEPIVAL-Interphako orVELOMET-Interphako by measuring the angle of inclination of the meniscus profile at two points in the horizontal distance ₁, and ₂ from a flat vertical wall. The method and its accuracy are described and tests for the surface tension are given.

     

Die gasvolumetrische Analyse,als Hülfsmittel für wissenschaftliche,agriculturchemische und technische Untersuchungen

Analytical and Bioanalytical Chemistry -