Vapour–liquid equilibrium measurements and correlation for the pentafluoroethane (R125) + n-butane (R600) system

Mixtures formed by hydrocarbons (HC) and hydrofluorocarbons (HFC) are considered promising possible substitutes for the chlorinated refrigerants and for HFC with high global warming potential (GWP). Following our studies on this kind of systems, vapour–liquid equilibria (VLE) experimental data for the R125 + R600 system were measured at temperatures 278.15 and 298.15 K by means of a static analytical method, with preliminary recirculation of the mixture to get a faster equilibrium. The composition of both phases in equilibrium was measured by a gas-chromatographic method. In the experimental temperature range, the system shows a strong positive deviation from the Raoultʹs law, even if it does not present an azeotropic composition. The VLE data were correlated by different equations of state involving various mixing rules, enabling a comparable analysis of their correlating ability of strongly non-ideal systems.