A quaternary system containing three solutes e.g. ethanol, diethylene glycol (DEG), and triethylene glycol (TEG) in benzene at 298.15 K and 1.0125 x 10⁵ Pa was studied. On-line simultaneous measurements using a densitometer and a refractometer were utilized to determine bulk solution density and refractive index, respectively. Response surface models were employed in total molar volume and total molar refraction to determine partial molar volume, partial molar refraction, electronic polarizability and molecular radii of each solute from dilute multi-component data alone. An experimental design in the concentration range 0.006 < x_solute-i < 0.022 was explored, optimizing the metric distance among the solutes to avoid clustering. The results determined from multi-component system were very consistent with literature values (obtained from binary systems) as well as those obtained from our separate binary experiments.