Transport properties of nonelectrolyte liquid mixtures—III. Viscosity coefficients for n-octane, n-dodecane, and equimolar mixtures of n-octane + n-dodecane and n-hexane + n-dodecane from 25 to 100°C at pressures up to the freezing pressure or 500 MPa

Abstract

Viscosity coefficients measured with an estimated accuracy of 2% using a new design of self-centering falling body viscometer are reported for n-octane, n-dodecane, and equimolar mixtures of n-octane + n-dodecane and n-hexane + n-dodecane at 25, 50, 75, and 100°C at pressures up to the freezing pressure or 500 MPa. The data for a given composition at different temperatures and pressures are very satisfactorily correlated by a plot of ή, defined as 10⁴ηV^2/3/(MT)^1/2 in the cgs system of units or, generally, 9.118×10⁷ηV^2/3/(MRT)^1/2, versus logV′, where V' = V · V ₀(T _R)/V ₀(T) and V ₀ represents the close-packed volume at temperature T and reference temperature T _R. The experimental results are fitted, generally well within the estimated uncertainty, by the equation

$$\ln \eta ' = - 1.0 + \frac{{BV_0 }}{{V - V_0 }}$$

, where B and V ₀ are temperature and composition dependent. Values of B and V ₀ for the mixtures are simply related to values for the pure liquids. The binary mixing rule of Grunberg and Nissan is investigated. Values of the mixing parameter G are positive, tend to increase with increases in pressure, and also increase with increases in difference in carbon number of the two pure components.