Phase transformations and critical properties of the $\rm C_3\rm H_7\rm OH$–$\rm C_7\rm H_{16}$ system

The experimental values of the $(p{,}~\rho{,}~T)_x$ dependences for the $1$-propanol–$n$-heptane system with compositions $x~(0.2{,}~0.38{,}~0.5{,}$ and $0.8$ mole fractions of $n$-heptane$)$ at phase transformations $($liquid–vapor$) \rightleftarrows$ liquid and $($liquid–vapor$) \rightleftarrows$ vapor, found from figurative kinks (bending points) of isochores in the $(p{,}~T)$ phase diagram, and the values of its critical parameters, estimated based on the analysis of the curvature of the phase diagram isochores and isotherms in the critical region, are presented. The dependence of the pressure of saturated mixture vapor $p_s = f(\rho_s{,}~T_s)_x$ along the phase-coexistence curve is described by the thermal equation of state in the virial form: expansion of the compressibility factor $Z_s = p_s/(RT_s\rho_{ms})$ into series in powers of reduced density and reduced temperature. The average relative error of deviations of the calculated pressure values from experimental ones is $1\%$. The temperature dependence of the density of the system along the equilibrium curve for liquid–vapor phases is described by two power-law functions: in the entire range of parameters and in the symmetric part of the curve $(0 < \tau < 0.01)$ at the critical exponent $\beta_0 = 0.370 \pm 0.002$. The average relative error is $0.8\%$ and $0.6\%$, respectively.