P–ρ–T and Ps–ρs–Ts properties of methanol + water and n-propanol + water solutions in wide range of state parameters

The P–ρ–T and Ps–ρs–Ts properties of methanol + water and n-propanol + water solutions in a wide range of state parameters have been investigated in a constant volume piezometer installation. The experiments were carried out for the methanol + water solutions in the temperature range 298.15 to 523.15 K, at mole fractions of methanol of x = 0.25, x = 0.50, x = 0.75, from the bubble point pressure up to 60 MPa and also for n-propanol + water solutions in the temperature range 373.15 to 573.15 K, at the x = 0.25, x = 0.50, x = 0.75 mole fractions of n-propanol, in the pressures range 0.1 to 5.25 MPa, in the 0.6628–118.6103 kg m−3 density interval. The experimental uncertainties are ΔT = ± 3 mK for temperature, ΔP = ± 5×10−2×P for pressure, Δρ = ± 3×10−2×ρ for density in liquid phases, and Δρ = ± 9×10−2×ρ in the vapor phase. A new equation of state was derived for correlation of the experimental data of methanol + water solutions. The experiments could be reproduced with deviations not exceeding experimental uncertainty. The data obtained for the n-propanol + water solution allowed us to establish the equation of state in virial form and thus the second and the third virial coefficients are calculated. The virial coefficients were obtained by two independent methods, namely, graphical and analytical. The temperature and mole fraction dependence of the coefficients of the equations of state are described.