Phase transformations in water-aliphatic alcohol binary systems

The parameters of liquid-vapor phase transitions $p_s$, $\rho_s$, $T_s$ and critical points $p_c$, $\rho_c$, $T_c$ were determined from the experimental data on the $p$, $\rho$, $T$, $x$-dependences of aqueous solutions of aliphatic alcohols (methanol, ethanol, $n$-propanol) that contain $0.2$, $0.5$, and $0.8$ mole fractions ($x$) of ethanol and correspond to single-phase (gas, liquid), two-phase, or subcritical areas. The dependence of the pressure of saturated vapor in solutions on the temperature and density was described by means of the expansion of the compressibility factor $Z=p/RT\rho_m$ in powers of the density and temperature along the coexistence curve away from the critical point. The temperature dependence of the density of solutions along the coexistence curve and inside the critical area was fitted using the power functions of parameters $\omega\sim\tau^{\beta_i}$, $\tau=(T-T_c)/T_c$ and $\omega=(\rho_{1,v}-\rho_c)/\rho_c$.