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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 317 (1981), S. 845-852 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Dispersion bedingt in Bereichen, in denen Flüssigkeiten infrarote Strahlung absorbieren, eine WellenlÄngenabhÄngigkeit der Reflexion. Bei Flüssigkeitsküvetten mit Schichtdicken unter 5 Μm kann dieser Effekt eine merkliche VerfÄlschung der gemessenen Absorptionsbanden verursachen. Sein Einflu\ auf die integrierte IntensitÄt, maximale IntensitÄt, Bandenlage und Bandensymmetrie wird im Detail für unterschiedliche Küvetten diskutiert. Bei den Simulationsuntersuchungen wird von einer IntensitÄtsverteilung der Adsorptionsbanden nach Cauchy und Gauss ausgegangen. Solange der mittlere Brechungsindex der untersuchten Substanz dem Brechungsindex der Fenster Ähnlich ist, kommt es lediglich zu einer Bandenverschiebung. Die BandenflÄche und Bandensymmetrie werden im Rahmen der Me\genauigkeit nicht verÄndert. Die Bandenverschiebung kann jedoch durchaus 5 cm− betragen. Für andere Fenstermaterialien können die gemessenen BandenflÄchen wie auch die maximale IntensitÄt sowohl niedriger als auch höher als die wahre BandenflÄche ausfallen. Ein Verfahren zur Korrektur der gemessenen BandenflÄchen wird angegeben. Die me\technische Verringerung der DispersionsverfÄlschung durch Anordnung von mit Probe gefüllten Küvetten unterschiedlicher Schichtdicke im Me\- und Vergleichsstrahl wird diskutiert.
    Notes: Summary Dispersion causes reflectance to be wave number dependent in regions where infrared radiation is absorbed. In the case of cells for liquids with a path length below 5 Μm this effect may distort measured absorption bands appreciably. The influence of this effect on integral intensity, maximum intensity, band position and band symmetry is discussed in detail for different window materials. It is assumed that the intensity distribution of infrared bands follows Cauchy or Gauss functions. If the refractive indices of a liquid sample and the window are similar, only the band position is shifted to lower wave numbers. Area and symmetry remain unchanged within the experimental uncertainty. The position of the band may be shifted for as much as 5 cm−. For other window materials the measured apparent band area and maximum intensity may be lower or higher than the true one. A procedure for correcting the measured band areas is given. The effect of placing a sample-filled cell of different path lengths in the sample and the reference beam is also discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 70 (1998), S. 1517-1525 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dioxins - Task for Environmental Engineering Two decades of the environmental history of dioxins, i.e. of PCCDs and PCDFs, are examined, with the main emphasis being placed on developments in Germany. After a brief consideration of the important, environmentally relevant properties of dioxins, interest is focussed on the course of the Seveso incident of 1976. The environmental effects of dioxins observed in Seveso received global publicity. In the following years our knowledge of the analysis and toxicology of this group of substances greatly improved and the production of dioxins in the aromatics sector of the chemical industry was drastically reduced. In the 1980s, discussions concentrated on the formation of dioxins in waste incineration. The results obtained during this period led to the present situation in which waste incineration is no longer a significant source of dioxin emission in Germany. The greatest known source of dioxins in Germany is in the metallurgical industry. By the year 2000 this dioxin source will also have been largely eliminated.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Use of Biocompounds for Degradation of Chlorinated Hydrocarbons in Treatment of Ground Water and Waste Water.Process engineering approaches to waste water treatment using immobilised microorganisms (MO) permit greater biomass concentrations in the bioreactor and hence higher conversions per unit time. Moreover, the biofilms formed assure favourable conditions for degradation specialists. Immobilisation of microorganisms is feasible on both static and freely mobile supports. Use of the latter permits modification of the flow conditions in the reactor.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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