The density (rho) and the refractive index (n) have been experimentally determined for the ethylbenzene (1)-octane (2)-propylbenzene (3) ternary system in the entire variation range of the composition, at three temperatures: 298.15, 308.15 and 318.15 K and pressure 0.1 MPa. The excess thermodynamic properties that had been calculated based on the experimental determinations have been used to build empirical models which, despite of the disadvantage of having a greater number of coefficients, result in much lower standard deviations in comparison with the Redlich-Kister type models. The statistical processing of experimental data by means of the multiple linear regression method (MLR) was used in order to model the excess thermodynamic properties. Lower standard deviations than the Redlich-Kister type models were also obtained. The adjustment of the excess molar volume (V-E) based on refractive index by means of the Multiple linear regression of the SigmaPlot 11.2 program was made for the ethylbenzene (1)-octane (2)-propylbenzene (3) ternary system, obtaining a simple mathematical model which correlates the excess molar volume with the refractive index, the normalized temperature and the composition of the ternary mixture: V-E =A(0) + A(1)X(1) +A(2)X(2) +A(3)(T/298.15)+A(4)n for which the standard deviation is 0.03. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.