Densities, ρ 123, and speeds of sound, u 123, of 1-methyl pyrrolidin-2-one (1) + benzene or methyl benzene or cyclohexane (2) + propan-2-ol (3) ternary mixtures have been measured over the entire composition range at 308.15 K and atmospheric pressure. The resulting ρ 123 and data were utilized to predict excess isentropic compressibilities, $(\kappa_{S}^{\mathrm{E}})_{123}$ , of the studied (1+2+3) mixtures. The observed and $(\kappa_{S}^{\mathrm{E}})_{123}$ data have been analyzed in terms of Graph theory (which involved the topology of a molecule). It has been observed that and $(\kappa_{S}^{\mathrm{E}})_{123}$ values determined by Graph theory compare well with their corresponding experimental values.