Critical exponent for the viscosity of four binary liquids

Published

September 15, 1988

Author(s)

Robert Berg, Michael Moldover

Abstract

We have measured the viscosity of four binary mixtures near their consolute points: (1) methanol + cyclohexane, (2) isobutyric acid + water, (3) nitroethane + 3-methylpentane, and (4) 2-butoxyethanol + water. The viscosity data are consistent with the power-law divergence: eta |T- Tc|^-y, with an apparent viscosity exponent in the range 0.0404 < y < 0.0444. Recent theoretical estimates for yare near 0.032, which is outside the experimental range. The value of y is independent of whether the critical point is an upper or a lower consolute point and of whether the approach toward Tc is at constant pressure or at constant volume. Our torsion oscillator viscometer is unique in its simultaneous low frequency ( 1 Hz) and low shear rate ( -0.1 s-1), allowing its use close to the critical point before encountering non-Newtonian fluid behavior associated with critical slowing down. Nevertheless, we find quantitative evidence for viscoelasticity near the critical point.

Citation

Chemical Physics

Volume

89

Pub Type

Journals

Citation

Berg, R. and Moldover, M. (1988), Critical exponent for the viscosity of four binary liquids, Chemical Physics (Accessed June 6, 2026)

Additional citation formats