Viscosities of iodobenzene + n-alkane mixtures at (288.15–308.15) K. Measurements and results from models

Abstract

Kinematic viscosities were measured for iodobenzene + n-alkane mixtures at (288.15-308.15) K and atmospheric pressure. The corresponding dynamic viscosities (η) were also determined using density data previously obtained in our laboratory. This set of data was employed to calculate Δη (deviations in absolute viscosity) and magnitudes of viscous flow. In addition, the correlation equations: McAllister, Grunberg-Nissan, Fang-He, and the Bloomfield-Dewan´s model were applied to the systems: iodobenzene, or 1-chloronaphthalene, or 1,2,4-trichlorobenzene, or methyl benzoate or benzene or cyclohexane + n-alkane. It is remarkable that, within the Bloomfield-Dewan´s model, residual Gibbs energies were calculated using DISQUAC with interaction parameters available in the literature. From the dependence of UmVE (isochoric molar excess internal energy) and Δη with n (the number of C atoms of the n-alkane), it is shown that the loss of fluidization of mixtures containing iodobenzene, 1,2,4-trichlorobenzene, or 1-chloronaphthalene when n increases can be ascribed to a decrease upon mixing of the number of broken interactions between like molecules. The breaking of correlations of molecular orientations characteristic of longer n-alkanes may explain the decreased negative Δη values of benzene mixtures with n =14,16. The replacement, in this type of systems, of benzene by cyclohexane, leads to increased positive Δη values, probably due to the different shape of cyclohexane. On the other hand, binary mixtures formed by an aromatic polar compound mentioned above and a short n-alkane show large structural effects and large negative Δη values. From the application of the models, it seems that dispersive interactions are dominant and that size effects are not relevant on η values. The free volume model provides good results for most of the systems considered, since deviations are less than 6% for 20 mixtures from the 29 solutions under study, and only 4 systems show deviations higher than 10%, with a maximum deviation of 15%. Results improve when, within the Bloomfield-Dewan’s theory, the contribution to η of the absolute reaction rate model is also considered.