Densities and excess molar volumes of thiophene + heptane and thiophene + octane at temperatures between (313 K and 363) K and pressures up to 25 MPa using three calibration methods

Abstract

New compressed liquid densities (ρ) of thiophene + heptane and thiophene + octane are reported in the temperature range from (313 to 363) K, with pressure up to 25 MPa. The compositions are x(1) = 0.1049, 0.2471, 0.5097, 0.7494, and 0.8994 for thiophene (1) + heptane (2), and x(1) = 0.1042, 0.2530, 0.5037, 0.7516, and 0.8988 for thiophene (1) + octane (2). The experimental system uses a vibrating tube densimeter (VTD) and three calibration methods (the first uses hexane and water, the second uses nitrogen and water, and the third uses water and applying vacuum to the VTD as calibration reference fluids). The reported density data are determined using the third method, which notifies the lowest uncertainty and estimates a maximum relative expanded uncertainty (k=2) of 0.21 % in the temperature range from (313 to 363) K and pressures up to 25 MPa. The pure compound densities were calculated from previous density measurements represented by the Pimentel-Galicia model. This empirical correlation of the pure compounds was used before for the excess molar volume calculation. The experimental data of the mixtures reported in this work were modeled by the Pimentel-Galicia model at each composition with deviations not higher than 0.07 %. The combined standard uncertainty for composition (considering the purities of the samples) is ucx= 0.0026. Finally, the isothermal compressibility and isobaric thermal expansivity were evaluated from density data.