Collisional depolarization of NO2 fluorescence as studied by Hanle effect measurements

We report on collisional depolarization of NO₂ fluorescence with use of Hanle effect (zero magnetic field level crossing) experiments. Single fine structure levels of NO₂ in several regions of the visible absorption spectrum predominantly near 593 nm and 514 nm are prepared by selective optical excitation and the depolarization of the fluorescence light versus a magnetic field is investigated. We find that the Hanle signal is in general a superposition of two Lorentzian shaped signals, each with a characteristic dependence on light intensity and NO₂ pressure. For NO₂ pressures >1 µ bar the collisional depolarization follows simple Stern-Volmer kinetics. However, an unusual pressure dependence is observed at NO₂ pressures <1 µ bar. In the same pressure range (<1 µ bar) we see also an unexpected resonance with significantly different properties as the Hanle signal.     

Synthesis of 2,2,4-triphenyl-3-propenoyl-3,4-dihydro-2H-benzopyran via a lithiated allene

Synthetic routes to 2,2-disubstituted chromanes and their hetero-ring-unsaturated analogues are briefly reviewed. A variety of common alkylating agents has been involved in such routes. Here, however, the alkylating agent is the lithiated form of 4-tetrahydropyran-2-yloxybuta-1-2-diene V. This reacted with benzophenone to give XIV. The synthesis of chromane XIV is here reported for the first time. The route to XIV is also both new and may prove versatile to other hetero-ring-substituted chromanes.     

Effects of molecular structure and environment on the photodimerization of substituted anthracenes

Photochemical and photophysical studies of a number of 9-substituted anthracene sandwich pairs in their corresponding photodimer crystal matrices have been carried out. Corresponding studies have also been made in methylcyclohexane matrices at 6 K. Photodimerization of the 9-methyl, 9-chloro and 9-cyano derivatives in the photodimer matrices occurs at 6 K with unit quantum yield. The presence of excimer fluorescence from sandwich pairs indicates the lack of a perfect topochemical orientation while activation processes, leading to photodimerization, involve molecular re-orientation from more stable ground state configurations which are achieved within the constraints imposed by the solvent or crystalline cage.     

On the loss of cadmium, antimony and silver during dry ashing of biological material

Summary The loss of cadmium, antimony and silver during dry ashing of marine weeds, mussels and shrimps was studied with the aid of radioactive tracers. Except for antimony all biological material was labelled by uptake of the radioactive tracers by the organisms while still alive. At an ashing temperature of 500° C and below no significant loss by volatilization of these elements occurs. The results obtained at higher temperatures with cadmium show that the behaviour of this element may depend on the composition of the organic material. Retention on the wall of quartz crucibles did not cause serious losses.

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Über den Verlust an Cadmium, Antimon und Silber bei der Trockenveraschung von biologischem Material

Zusammenfassung Mit Hilfe radioaktiver Tracer wurden die Verluste an Cadmium, Antimon und Silber bei der Trockenveraschung von Seetang, Muscheln und Krabben untersucht. Mit Ausnahme von Antimon wurden alle Materialien mit den Tracern durch Aufnahme im lebenden Zustand markiert. Bei Veraschungstemperaturen von 500° C und darunter konnten keine signifikanten Verluste durch Verflüchtigung der Elemente festgestellt werden. Das Verhalten von Cadmium bei höheren Temperaturen kann von der Zusammensetzung des organischen Materials abhängen. Verluste durch Haften an der Wand des Quarztiegels waren unbedeutend.

     

Syntheses and degradations of fluorinated heterocyclics III. Perfluoroalkyl and perfluoroalkylether-1,3,4-oxadiazoles

2,5-Bis(perfluoro-n-heptyl)-, 2-perfluoroalkylether-5-perfluoro-n-heptyl-, and 2,5-bisperfluoroalkylether-1,3,4-oxadiazoles were synthesized and characterized. 2,5-Bis(perfluoro-n-heptyl)-1,3,4-oxadiazole was thermally and hydrolytically stable at 325°C; however, in the presence of air, degradation took place at 235°C. The perfluoroalkylether analogue exhibited thermal and hydrolytic stability at 325°C; it was found to be unaffected by Jet-A fuel and air at 235°C. At 325°C in air some degradation occured as evidenced by volatiles production, oxygen consumption, and 96% starting material recovery.     

Reactions of sodium sulphide—I : With compounds containing hydroxyl groups

Aqueous solutions of sodium sulphide (ca 10%) reagent were reacted at 250° with compounds containing OH groups. This work was part of a programme designed to test the usefulness of the Na₂S solution degradation technique for determining the primary structure of humic acids. The compounds reacted here and the principal products detected (shown in brackets) were: cinnamyl alcohol (benzyl alcohol, benzoic acid, 3-phenylpropan-1-ol, 3-phenylpropionic acid), benzyl alcohol (little reaction), 3-phenylpropan-1-ol (little reaction), 1,2-dihydroxy-1-phenylethane (phenylacetic acid, acetophenone, 1-phenylethanol), catechol and hydroquinone (recovered starting compounds+ polymer products). Sodium hydroxide gave the same products with cinnamyl alcohol, but in different proportions. Possible mechanisms for these reactions are discussed.     

X-ray diffraction and morphology of crystalline,hard, elastic materials

Summary X-ray diffraction and electron microscopic results on several crystalline polymers which demonstrate elastic properties (polypropylene, Celcon^®, poly-4-methyl-pentene) are reported. Photographic small angle X-ray diffraction techniques provided considerable qualitative information, concerning the morphological features of these elastic materials both as extruded, annealed and during extension. Lamellar thickness, thickness distribution and perfection of lamellae could be estimated. Lateral order features and orientation of the lamellar structures were obtainable from the sharpness and length of the equatorial wide angle diffraction arcs. Electron microscopic results essentially confirm the morphological features postulated on the basis of the X-ray results. These morphological features are discussed in terms of a general structural model which appears consistent with the mechanical properties of these materials.

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Zusammenfassung Röntgenbeugung und elektronenmikroskopische Daten von einigen kristallinen Polymerprodukten mit elastischen Eigenschaften (Polypropylen, Celcon, Poly-4-methylpenten) werden berichtet. Die photographische Röntgen-Kleinwinkelmethode liefert wichtige qualitative Messungen der morphologischen Struktur dieser elastischen Materialien in den Zuständen sowohl wie hergestellt als auch nach Tempern und während des Dehnungsprozesses. Die Dicke der Lamellen, ihre Dikkenverteilung und die Güte der Lamellen konnten abgeschätzt werden. Die laterale Ordnung und die Orientierung der Lamellen kann aus Weitwinkelbeugungsdaten abgeleitet werden. Die Elektronenmikroskopie bestätigt die Morphologie, die aus Röntgendaten folgt. Ein allgemeines Strukturmodel dieser Morphologie, das im Einklang mit den mechanischen Eigenschaften dieser Produkte steht, wird diskutiert.

     

Modern Analysis

The important advances being made in modern analytical methods are indicative of the fundamental changes that are occuring in the theory and practice of “analytical chemistry”. “Information optimization” demands a new approach in teaching and research, and calls for the intergration of chemistry with other scientific and technical disciplines.     

Darstellung verschiedener 2,6-disubstituierter 4-Sulfanilamidopyrimidine 7. Mitt. über neue N1-substituierte Sulfanilamide

Zusammenfassung Im 2,6-Dichlor-4-aminopyrimidin wurden die beiden Chloratome wahlweise gemeinsam oder zweistufig gegen Alkoxyoder Alkylmercaptoreste ausgetauscht. Partiell reagiert bevorzugt das 2-ständige Halogenatom, während das 6-ständige derberer Bedingungen zum Umsatz bedarf. Die so erhaltenen gleichartig oder verschieden in 2,6-Stellung durch Alkoxy- bzw. Alkylmercaptoreste substituierten 4-Aminopyrimidine wurden mit N-Carbäthoxysulfanilsäurechlorid acyliert und durch alkal. Verseifung die entsprechenden 2,6-disubstituierten 4-Sulfanilamidopyrimidine gewonnen.     

Investigation of HfO(+) interference in the determination of platinum in a catalytic converter (cordierite) by inductively coupled plasma mass spectrometry

The determination of Pt in cordierite is subject to strong interference by spectral overlap from HfO(+) ions with all Pt isotopes. Two mathematical correction methods based on the HfO(+)Hf(+) ratio and a method for the chemical separation of Hf based on adsorption chromatography and isotope dilution were investigated to correct for this interference. Flow infection was used to prevent clogging of the cone orifice. To enhance the sensitivity and thus lower the detection limit, thermospray nebulization was used for sample introduction and the method was compared with pneumatic nebulization. In addition, the memory effects were evaulated for both systems. Analysis of artificial solutions (1 ng Pt ml(-1)) yielded results within 3% of the true value. Th Pt content (ca. 50 ng g(-1)) of a cordierite sample, previously exposed to exhaust gases, could be determined with precisions of about 10-25% and the results agreed with earlier determinations by other workers.