Phase Transitions of n-Hexane–Water Binary Mixtures (0.5 Mole Fraction)

By the method of constant volume piezometer among the isochores new values of p,T and p,ρ,T - relations of n-hexane– water binary mixture (0.5 mole fraction) in three phase (llg) and two phase (ll and lg, l-liquid, g – gas) regions, over the wide temperature range from 373.15 to 673.15 K, pressures between 0.2 and 56 MPa and densities between 55 kg/m 3 and 554 kg/m 3 are obtained. Using isochoric P-T break point technique the values of the phase transition parameters (llg ⇄ll, llg⇄lg and ll⇄lg) on p,T – plane were determined and phase coexistence curves in different thermodynamic sections ( p,ρ,T ) X were built. 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 s =p s V ms /RTs=p s /RT s ρ ms into a power series of density ω=ρ s /ρ c and temperature τ= T s /T c . Z s = p s / R T s ρ m s = 1 + ∑ i = 1 m ∑ j = 0 n a i j ω i / τ j , Z s = p s / R T s ρ m s = 1 + ∑ i = 1 m ∑ j = 0 n a i j ω i / τ j , where ρ m -molar density (mol/m 3 ), R=8.314-gas constant (J/mol⋅K). The average relative deviation of calculated values of pressure from experimental ones is not more than 0.1%.