Phase transitions and critical properties of 1-propanol–n-hexane system

Abstract

By using experimental data on p, T, x and p, T, ρ, x - relations of 1-propanol- n-hexane mixtures (0.2, 0.5, 0.8 and 0.9 mol. fraction of n-hexane x) and the method of isochore fracture p = f (T)ρ,x at two-phase (liquid-gas), one-phase (liquid, gas), near-critical and supercritical region liquid ↔ gas (ps, ρs, Ts) phase transition parameters are determined. And parameters of critical points (pc, ρs, Tc) are determined by the grapho-analytical method combining with scaling behavior. The dependence of pressure from temperature, density and composition along the phase coexistence curve is described by three parameter polynomial represented by expansion of the compressibility factor Z = p/RTρ into a power series of density ω = ρ/ρk and temperature , and .The average relative deviation of calculated values of pressure from experimental ones is 1%. The dependence of temperature from density along the liquid ↔ gas phase coexistence curve is described by equations: far from critical points ρ = ρk (1 ± B0τβ0 + B1τβ1 ± B2τβ2 + …), and in the symmetrical part of equilibrium curve (ρf – ρg)/2ρk = B0τβ0 + B2τβ2 + B4τβ4 + …, where τ = (T – Tk )/Tk and ω = (ρ – ρk)/ρk. Average relative error is 1.47%.