Dielectric constants of binary mixtures of methyl isobutyl ketone (MIBK), an extractant used in nuclear industry, with non-polar solvents, viz., benzene, CCl4 and p-xylene have been measured at 303 K. The results are used to compute linear correlation factor, excess molar polarization and excess free energy of mixing in these mixtures using the Winkelmann-Quitzsch equation to interpret the liquid structure. The trend of variation of these factors indicates gradual conversion of alpha-multimers to beta-multimers on adding a non-polar diluent to MIBK.