Excess molar volumes, changes of refractive indices, and changes of isentropic compressibilities of the ternary mixture benzene + 2-methyl-2-butanol + 1-pentanol, and the binary subsystem 2-methyl-2-butanol + 1-pentanol have been calculated from density, refractive index, and speed of sound measurements at 298.15 K and atmospheric pressure. The Redlich-Kister and the Cibulka equation were used for correlating binary and ternary properties, respectively. ERAS model interaction parameters of the binary systems concerned were computed. A good representation of the behaviour of the property is obtained. The Soave-Redlich-Kwong and the Peng-Robinson equations of state were applied, in combination with simple mixing rules, Binary parameters were calculated from experimental excess molar volumes, and used to predict the ternary property, yielding lower deviations.