A reevaluation of the viscosity exponent for binary mixtures near the consolute point

Abstract

A reevaluation of the critical exponent of the viscosity anomaly for binary mixtures close to the consolute point is presented. Using published data we make a systematic, consistent study in which corrections due to shear gradients and frequency effects are included and the effect of the functional form for the background viscosity is critically examined. The result is that the value of the exponent is generally found to be larger than reported and larger than the most recent theoretical predictions.

Viscosity and diffusivity of a binary liquid mixture of critical composition: Study of the system 2-butoxyethanol/water

“…A review of experimentally determined values of z, has shown that a large number of experimental data are consistent with the theoretical value of z,=0.065 [3,4]. Equation(3) represents the asymptotic behavior of the viscosity near the critical temperature.…”

Transport properties of 1,1-difluoroethane (R152a)

“…where Q is a system-dependent amplitude and where z = 0.063 is a universal critical exponent [58][59][60].…”

Estimation of critical amplitudes of the correlation length by means of calorimetric and viscosimetric measurements

“…Most available methods for measuring the dynamic viscosity entail introducing corrections in experimental viscosity values in order to obtain accurate g values [13]. Such corrections are based on OxtobyÕs theory [14,15] and are strongly dependent on n þ 0 , so using inaccurate values of this quantity can lead to spurious viscosity data in the immediate vicinity of the critical point.…”