Speed of Sound and Excess Properties of (Ethanol + Isooctane) Binary System

We report the speeds of sound for the mixtures of ethanol (1) + isooctane (2) at 0.100, 0.300, 0.500, 0.700, 0.900 molar fractions of ethanol, respectively, at temperatures from 298.15 to 605.23 K along three isobaric lines from 3.0 to 7.0 MPa. On the basis of the experimental results and the literature density data, we evaluate the excess free length, excess acoustic impedance, and excess isothermal compressibility of ethanol (1) + isooctane (2) mixtures at 298.15 to 435.15 K and pressures below 5.0 MPa. Moreover, we fit the excess values by the Redlich–Kister polynomial equation. Finally, molecular interactions between ethanol and isooctane are analyzed.