High-Pressure Density of DL-Menthol/Octanoic Acid Eutectic Solvents

Due to the hydrophobicity, the eutectic solvents (ESs) composed of DL-menthol and octanoic acid have been considered as a kind of promising extraction solution. The thermophysical properties of the ESs are necessary for their wide applications. In this work, the high-pressure liquid densities of DL-menthol/octanoic acid ESs at five molar ratios (1:1, 1:2, 2:1, 1:3, and 3:1) were studied based on the vibrating method. The measurements were carried out from 293.15 to 363.15 K and at pressures up to 70 MPa. The effects of temperature, pressure, and molar ratios on the density of the DL-menthol/octanoic acid ESs were analyzed. In addition, the experimental results were fitted by the Tait-type equation; the maximum deviation for the studied five solvents between experimental data and values from the Tait equation was less than 0.010%. The derived properties including isobaric thermal expansivity, isothermal compressibility, and internal pressure were calculated, and the effects of the temperature, pressure, and molar ratios on the derived properties were discussed.