Concentration Fluctuations in the Critical Region of the Binary Liquid 3-Methylpentane-Nitroethane.
MARYLAND UNIV COLLEGE PARK DEPT OF PHYSICS AND ASTRONOMY
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The intensity and Rayleigh linewidth have been measured as a function of temperature and scattering angle for light scattered by concentration fluctuations near the critical mixing point of the binary liquid mixture 3-methylpentane-nitroethane. The data were obtained at the critical concentration above Tc and on both sides of the coexistence curve below Tc. The susceptibility and the correlation length, xi, were determined as a function of the temperature from the intensity data. The decay rate Gamma of the concentration fluctuations was determined from the lindwidth measurements. The ratio of the correlation lengths at equal temperature intervals above and below Tc was obtained from a comparison of both the intensity and the spectral measurements taken in these two regions. The observed variation of Gamma with K xi was compared with the theory of Kawasaki. The authors also review some recent improvements in the Kawasaki theory, reported by Kawasaki and Lo and by Perl and Ferrell, in which the viscosity is properly treated as a k and xi dependent quantity.
- Physical Chemistry