Multiple Wavelength Extinction Technique for Particle Characterization in Dense Particle Clouds

In utilizing the advantages of extinction measurements in micron and especially submicron particle characterization, the properties of a multiple wavelength extinction technique have been the subject of extended theoretical studies. Furthermore, an experimental set-up was designed which provides high flexibility owing to its modular design. The performance of the technique described is demonstrated by a large variety of applications in aerosol and combustion research and in large-scale industrial systems. It was found to be a reliable tool in characterizing dense particulate systems.     

Depth profiling of latex blends of fluorinated and fluorine‐free acrylates with laser‐induced secondary mass spectrometry

We explored phase separation and self‐assembly of perfluoroalkyl segments at the surface of polymer films obtained from latices of semifluorinated acrylate copolymers and the corresponding latex blends of nonfluorinated and semifluorinated polyacrylates. With laser‐induced secondary mass spectrometry the fluorine distribution was measured after annealing above the minimum film‐forming temperature of the polymers up to a depth of several micrometers. Depth profiles of a semifluorinated acrylate homopolymer and latex blends thereof with fluorine‐free alkylacrylates with 25, 50, and 75 mol % semifluorinated acrylate as well as a copolymer comprised of alkyl acrylate and semifluorinated acrylate (50/50 mol %) were investigated. In the case of latex blends containing both semifluorinated polyacrylates and fluorine‐free or low‐fluorine polymers, self‐assembly accounted for enrichment of the perfluoroalkyl segments at the surface. Coatings exhibiting low surface energy and having a substantially reduced total fluorine content were obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 360–367, 2003     

Invers-voltammetrische Bestimmung von Chrom(III)

Solutions of Cr(III) salts containing ammonium hydroxide and ammonium salts can be determined after proper pretreatment by inverse voltammetry at carbon paste and glassy carbon electrodes. The determination may be performed, too, with organic solutions of the Cr(III) oxinate. Sensitivity is 5 × 10^?7 M (= 26 ng Cr/ml), standard deviation is in the range of 4–6%.     

Zur Erh?hung der Empfindlichkeit wechselstrompolarographischer Analysenverfahren

Zusammenfassung Die Verwendung eines selektiven Verstärkers zur Messung des Oberwellenanteils in der Wechselstrompolarographie wird beschrieben. Durch die Verminderung des Kapazitätsstromes wird eine 10–20 fach höhere Empfindlichkeit erzielt.Mit einer pseudostationären Hg-Elektrode läßt sich eine weitere 3–5fache Empfindlichkeitssteigerung erreichen.Die vorliegende Arbeit wurde in dankenswerter Weise durch Mittel der Deutschen Forschungsgemeinschaft und des Verbandes der Chemie ermöglicht.Herrn Prof. Dr. F. Strassmann danke ich für die Bereitstellung von Institutsmitteln.Herrn Prof. Dr. Dr. W. Herzog (Institut für Elektrotechnik der Universität Mainz), der den Bau des selektiven Verstärkers in seinem Institut unterstützte, sei an dieser Stelle ebenfalls besonders herzlich gedankt.     

Eine quantitative Korrektur des durch gefärbte Lösungen hervorgerufenen Quench-Effektes bei der Flüssigscintillationsmessung

Analytical and Bioanalytical Chemistry -     

The electronic structure of benzvalene : Photoelectronspectroscopic studies

The photoelectron(PE)spectrum of tricyclo[3.1.0.0^2,6] hex-2-ene(benzvalene 1) has been recorded. The first four bands in the PE spectrum of 1 can be assigned to transitions to ²B₂, ²A₁, ²A₂ and ²B₁ states of 1¹. This assignment is discussed in terms of the results of semiempirical and ab initio calculations on 1. Furthermore the highest occupied MO's of 1 are derived qualitatively from an interaction diagram between a distorted bicyclobutane and an ethylene moiety.     

Beitr?ge zur Bestimmung von Spurenverunreinigungen in UO2-Kernbrennstoff

Zusammenfassung Die für die Bestimmung geringer Gehalte an Phosphor, Silicium, Fluor, Chlor, Lithium, Natrium, Calcium und Kohlenstoff in UO₂-Kernbrennstoff angewandten chemischen Analysenverfahren werden beschrieben. Durch Kombination einfacher und blindwertfreier Abtrennungsverfahren (Extraktionen und Pyrohydrolysen) mit empfindlichen physikalischchemischen Bestimmungsmethoden (Spektralphotometrie, Flammenphotometrie, coulometrische Titration) lassen sich Nachweisgrenzen zwischen 0,1 und 10 ppm bei Probeneinwaage von 0,5–1 g UO₂ erreichen. Der Zeitaufwand für die Analysen kann durch simultane Bestimmung zweier oder dreier Elemente in einem Arbeitsgang niedriggehalten werden. Die beschriebenen Verfahren haben sich bei Reinheitskontrollen von Kernbrennstoffen gut bewährt.

---

Summary Analytical methods have been developed for the determination of trace amounts of phosphorus, silicon, fluorine, chlorine, lithium, sodium, calcium, and carbon in UO₂ of nuclear purity. By combination of simple and rapid separation procedures (extraction, pyrohydrolysis) with highly sensitive methods of determination (spectrophotometry, flame photometry, coulometric titration) detection limits of 0.1–10 ppm have been obtained with sample sizes of 0.5–1 g. In order to reduce the time needed for analysis, some of the above elements are determined simultaneously. The methods described have been successfully applied to the purity control of nuclear fuels.

---

---

Herrn Dr. W. Gebauhr danken wir für wertvolle Anregungen und Diskussionen.