The speed of sound in six binary mixtures (1,3-dioxane, or 1,4-dioxane + 2,2,4-trimethylpentane, or benzene, or tetrachloroethene) was measured at T = 298.15 K. Isentropic and isothermal compressibilities and isochoric heat capacity were estimated from the speed of sound by using the excess volume, excess isobaric heat capacity and excess thermal expansivity of the mixtures reported in previous papers. The excess functions of the mixtures of both isomers behave in similar ways so each other for corresponding solvents. Properties of the opposite non-polar solvents have a great influence on the behaviour of the excess functions.