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 104ηV2/3/(MT)1/2 in the cgs system of units or, generally, 9.118×107ηV2/3/(MRT)1/2, versus logV′, where V' = V · V0(TR)/V0(T) and V0 represents the close-packed volume at temperature T and reference temperature TR. 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 V0 are temperature and composition dependent. Values of B and V0 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.