Generalized relation between surface tension and viscosity: a study on pure and mixed n-alkanes

Abstract

A generalized relation is presented to correlate liquid–vapor surface tension with viscosity, both for pure compounds and mixtures. Plots of different data sets verify that the natural logarithm of the surface tension is linear with the reciprocal viscosity, with slope-dependent on the molecular weight and constant intercept for n-alkanes with chain length greater than n-C 10H 22. For these, the value of the intercept can be related to the surface tension at the temperature of homogeneous nucleation, where the reciprocal viscosity tends to zero. The relations found for the slope and intercept of pure components are also shown to be valid for mixtures, so that only a viscosity (or surface tension) value is required to calculate a surface tension (or viscosity). Some distillation cuts from crude oils of different origins were also presented. Although the linear relation is still valid, the proposed correlations for the slope and intercept of n-alkanes cannot be used, confirming that mixing rules and family specific correlations are required for fluids containing components of different families. The results presented on this work show how bulk transport and equilibrium surface properties can be interrelated.