Heats of mixing and phase behavior of several fluorocarbon + hydrocarbon and carbon-dioxide + hydrocarbon systems in their critical regions

Excess enthalpies of mixing, H{dollar}sbsp{lcub}rm m{rcub}{lcub}rm E{rcub}{dollar}, were measured over a large range of temperatures and pressures in the critical region for three binary systems consisting of a fluorocarbon + a hydrocarbon and five systems consisting of CO{dollar}sb2{dollar} + a hydrocarbon. The unusual characteristics of the H{dollar}sbsp{lcub}rm m{rcub}{lcub}rm E{rcub}{dollar}(x) curves in the critical region were discussed with relation to the physical interactions occurring in the mixtures, including the existence of coexisting liquid and vapor phases. A method for determining the liquid and vapor equilibrium phase compositions, where two phases exist, was presented. Results compared very well with the literature, where literature values were available. A procedure for determining the critical locus from the phase compositions using a critical exponent was outlined. Results for three of the CO{dollar}sb2{dollar} + hydrocarbon systems were obtained and they compared favorably with the literature values.; Two equations of state were used to model both the H{dollar}sbsp{lcub}rm m{rcub}{lcub}rm E{rcub}{dollar} and VLE values. Cross calculation of VLE using parameters determined from H{dollar}sbsp{lcub}rm m{rcub}{lcub}rm E{rcub}{dollar} correlations and vice versa was examined and found to yield poor results. The behavior of an adjustable interaction parameter was examined with respect to temperature dependence and equation of state dependence.