Dynamic scaling of the critical mixture perfluoromethylcyclohexane–carbon tetrachloride

Abstract

Ultrasonic attenuation, specific heats at constant pressure, static and dynamic light scattering as well as shear viscosity data of the perfluoromethylcyclohexane–carbon tetrachloride critical system have been re-evaluated in the light of the Bhattacherjee–Ferrell dynamic scaling model. The experimental sonic attenuation coefficients yield the theoretical form of the scaling function if a noncritical relaxation term is assumed to contribute to the total spectra in addition to the critical contribution. Evidence from noncritical ultrasonic spectra suggests the noncritical relaxation to be due to rotational isomerization of the perfluoromethylcyclohexane molecule. The amplitudes in the power laws of the fluctuation correlation length, the mutual diffusion coefficient and the relaxation rate of concentration fluctuations are ξ0 = (0.228 ± 0.021) nm, D0 = (1.24 ± 0.04) × 109 m2 s−1, and Γ0 = (47.5 ± 13) × 109 s−1, respectively. The amplitude of the critical term in the heat capacity is Cpc = (0.093 ± 0.002) J g−1 K−1 and the adiabatic coupling constant results as g = 0.126.