Determination of the thermodynamic properties of 1-propanol and 1-hexanol from speed of sound measurements under elevated pressures

The speed of sound in 1-propanol and 1-hexanol was measured in the temperature range from 293 K to 318 K and at pressures up to 120 MPa by the pulse-echo-overlap method. The density was measured under atmospheric pressure with a vibrating tube densimeter within the same temperature range. From the measurement results, the densities and heat capacities of 1-propanol and 1-hexanol at elevated pressures have been calculated. A short description of the calculation procedure was given. A satisfactory correlation of density, temperature, and pressure was achieved by means of the Tammann-Tait equation of state. The densities of the two alcohols calculated from the equation of state were found to be very close to those reported in the literature. However, the adjustable coefficients in the equation of state depend strongly on their initial values used in the nonlinear fitting procedure. Nevertheless, the use of any set of reliable coefficients leads to almost the same densities at a given temperature and pressure.