Atomic and Structural Contributions to Molar Refraction and Extension to Mixtures

Molar refraction of pure liquids has been calculated for well over a thousand substances, from an evaluated set of atomic and structural contributions. On an overall basis, the calculated values are in agreement with the experimental data, showing an average absolute deviation of 0.6%, and an average of maximum deviations of 2.1%. The effect of temperature on molar refraction has also been studied and found to show an average absolute deviation of 0.8%. Molar refraction of binary liquid mixtures has been estimated from the molar refraction of pure liquids (calculated from atomic and structural contributions) and the mole fraction by applying the linear rule. The results for 25 randomly studied mixtures showed an average absolute deviation of 0.4%. The effect of estimating molar refraction of pure liquids (or liquid mixtures) as described above on the values of the various physico–chemical properties, calculated employing molar refraction (or its equivalent for polar substances – molar polarization at the critical temperature) is found to be less than 2.8%.