The refractive indices, n(D), of pure benzene and 1,2-dichloroethane (DCE) and those of their binary mixtures have been measured over the whole composition range and at 298.15, 303.15, 308.15, 313.15, and 318.15 K. Using the experimental nD data, deviations in refractive indices, Delta n(D), molar refraction, Delta R-m, reduced free volume, Delta(V/R-m), and internal pressure, Delta P-int, have been estimated. Parameters of polynomial equations, which represent the composition dependence of physical and derived properties, are gathered. The results are discussed in terms of molecular interactions between the component molecules. Applicability of eight different refractive index mixing rules-Lorentz-Lorenz, Weiner, Gladstone-Dale, Heller, Arago-Biot, Newton, Eykman, and Oster's relation-is tested against the measured results, and good agreement has been obtained. Moreover, molecular radii, r, and average molecular radii (r(mix)) of the liquids and their mixtures have been calculated.