Critical point measurements on nearly polydisperse fluids

The critical temperatures, pressures and volumes of several mixtures containing CO 2 , C 2 H 6 , C 3 H 8 , and C 4 H 10 have been measured using a heavy walled, variable volume, cylindrical glass vessel. In each mixturre the relative proportions of the three hydrocarbon solutes to one another were changed; total solute mole fraction never exceeded 0.1. A detailed study of the mixture CO 2 + C 3 H 8 shows that the critical temperature exhibits a minimum at a C 3 H 8 mole fraction of 0.0265. Our mixture data are analyzed using a polydisperse model of dilute solutions.