Thermodynamics of n-alkane + dimethylsiloxane mixtures. Part 1.—Gas–liquid critical temperatures and pressures

Abstract

Gas–liquid critical temperatures Tcm have been determined for four mixtures: (i) n-hexane + hexamethyldisiloxane, (ii) n-octane + hexamethyldisiloxane, (iii) n-octane + octamethyltrisiloxane, and (iv) n-octane + 2,2,4,4-tetramethylpentane. Using a statistical model based upon the van der Waals one-fluid approximation, values of Tcm for each mixture are related to a parameter ζ which is proportional to the energy of interaction between the unlike molecular species. Gas–liquid critical pressures pcm are reported for mixtures (i), (ii) and (iii), and the results are discussed in terms of possible deviations from the Lorentz combining rule of collision diameters.