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  • Articles: DFG German National Licenses  (2)
  • 1985-1989  (2)
  • Lorentz-Lorenz relation  (1)
  • critical phenomena  (1)
  • microgravity  (1)
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  • Articles: DFG German National Licenses  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Surface tension, coexistence curve, and vapor pressure of binary liquid-gas mixtures (1986)
    Springer
    International journal of thermophysics 7 (1986), S. 41-51 
    Details
    ISSN: 1572-9567
    Keywords: capillary coefficient ; coexistence curve ; Lorentz-Lorenz relation ; mixtures ; refractive index ; surface tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The objective of this paper is to present measurements of the vapor pressure, capillary coefficient, and refractive index of four binary mixtures, CO2-SF6, R14-SF6, SF6-R13B1, and SF6-R22, at liquid-vapor equilibrium at different average concentrations. The measuring temperature range covered the entire liquid-vapor region from the triple line up to the critical point. The capillary coefficient was determined by means of the capillary rise method; the refractive index, by measuring the angle of refraction of a light beam passing through a prism and the sample. In order to obtain the liquid-vapor densities of pure substances the Lorentz-Lorenz relation can be used. However, in applying this relation to calculate the liquid-vapor densities of a mixture, one may need the concentrations of both the liquid and the vapor phase, which are, for the most part, quite different from the average concentration of the mixture. Calculating the concentrations of both fluid phases with the aid of an equation of state and comparing with measurements, we could show that the molar refraction coefficient of the mixtures can be simply determined from the average concentration and the molar refraction coefficients of their pure components. The surface tension of the mixtures could then be calculated from the measured capillary coefficient and the refractive index with the aid of the Lorentz-Lorenz relation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503797
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Isochoric specific heat of sulfur hexafluoride at the critical point: Laboratory results and outline of a spacelab experiment for the d1-mission in 1985 (1986)
    Springer
    International journal of thermophysics 7 (1986), S. 343-356 
    Details
    ISSN: 1572-9567
    Keywords: critical phenomena ; critical exponents ; isochoric specific heat ; scanning ratio calorimeter ; microgravity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The specific heat at constant volume cv shows a weak singularity at the critical point. Renormalization group techniques have been applied, predicting a universal critical behavior which has to be experimentally confirmed for different systems. In this paper an experiment is presented to measure the specific heat of SF6 along the critical isochore (ρc=0.737 g·cm−3), applying a continuous heating method. The results cover a temperature span of −1.5×10−2〈 τ〈1.70×10−2 [τ=(T−T c)/T c] and were strongly affected by gravity effects that emerge in the sample of 1-mm hydrostatic height near the critical point. Using regression analysis, data were fitted with functions of the form c v/R=A × ¦τ¦−α + B for the one-phase state and c v/R=A″ × ¦τ¦−α″ + B″ for the twophase state. Within their error bounds the critical values (α=α″=0.098, A″/A=1.83) represent the measurements for the temperature span 3.5×10−5〈 ¦τ¦〈2.0×10 −3, in good agreement with theoretical predictions. In order to exclude density profiles in the specimen, which are unavoidable in terrestrial experiments due to the high compressibility of fluids at the critical point and the gravity force, a space-qualified scanning ratio calorimeter has been constructed, which will permit long-term cv measurements under microgravity (μ-g) conditions. The experiment will be part of the German Spacelab mission in October 1985. The significant features of the apparatus are briefly sketched.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500160
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    Paper (German National Licenses)
    Fulltext
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