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  • peroxyoxalate reaction intermediate  (1)
  • vibrating-wire viscometer  (1)
  • 1995-1999  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 19 (1998), S. 391-401 
    ISSN: 1572-9567
    Keywords: gas viscosity ; high pressures ; high temperatures ; vibrating-wire viscometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The vibrating-wire technique has been applied to design a viscometer for precise measurements on gases in the temperature range 25 to 250°C at pressures from 0.1 to 40 MPa employing two Chromel wires with different radii. The technique has been improved to avoid the influence of higher harmonic modes and the degeneracy of perpendicular modes, to eliminate electromagnetic noise from the signal, and to minimize the influence of the magnetic damping. The decrement and frequency of the oscillation have to be determined by extrapolation to zero displacement, and wires with a perfectly smooth surface are needed to meet the requirements of the measuring theory. The viscosity measurements are characterized by a precision of ±0.05% at ambient temperature. Considering the uncertainty of the reference data used for calibration, the total uncertainty amounts to ±0.2% within the calibrated range of the boundary-layer thickness.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0894-3230
    Keywords: peroxyoxalate reaction intermediate ; chemiluminescent decomposition ; kinetics ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The peroxyoxalate system undergoes one of the most efficient chemiluminescence reactions and is the only one considered to involve an intermolecular chemically initiated electron exchange luminescence mechanism, with proven high efficiency. Several reactive intermediates have been proposed, which, upon interaction with a fluorescent activator, lead to excited-state generation. The synthesis and spectral characterization of 4-chlorophenyl O,O-hydrogen monoperoxyoxalate (1), a compound analogous to one of the proposed reactive intermediates, was recently reported. Here the results of a kinetic study on the chemiluminescent decomposition of this peracid 1, catalyzed by oxygen bases (potassium hydroxide, potassium tert-butoxide and potassium p-chlorophenolate) or nitrogen bases [pyridine, imidazole and 1,8-bis(dimethylamino)naphthalene] are presented. Based on the dependence of the observed rate constants on the base concentration, kinetic schemes are proposed for the catalyzed decomposition of 1 and rate constants are assigned to specific reaction steps. The results obtained with the nitrogen bases give further support in favor of 1,2-dioxetane dione as the reactive intermediate in the peroxyoxalate reaction. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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