Refractive index, molar refraction deviation and excess molar volume of binary mixtures of 1,4-dioxane with carboxylic acids

The refractive indices and densities of three carboxylic acids viz formic acid (FA), acetic acid (AA) and propionic acid (PA) in 1,4-dioxane (D) over the entire composition range have been measured at 293, 303 and 313 K. Refractive index and density data have been used to evaluate the molar refraction deviation Rm and excess molar volume [image omitted]. The values of Rm and [image omitted] for all the three binary mixtures have been found to be negative. However, a smaller positive trend in [image omitted] has been observed for the 1,4-D + PA mixture in the D rich region. Values of Rm and [image omitted] are more negative in the case of 1,4-D + FA, suggesting that intermolecular interaction is strongest between unlike molecules as compared to the other two binary mixtures. Further, various theoretical mixing rules for the prediction of refractive index of liquid mixtures have been applied to predict the refractive index of these binary mixtures. A critical analysis of these rules from the point of view of their applicability at different temperatures has been carried out.