PHASE-EQUILIBRIA AND CRITICAL PHENOMENA IN FLUID BINARY-MIXTURES OF 2,6,10,15,19,23-HEXAMETHYLTETRACOSANE WITH METHANE AND ETHANE UP TO 200 MPA

In order to study the size effect on the pressure dependence of immiscibility phenomena in fluid systems the phase equilibria in binary mixtures of 2,6,10,15,19,23-hexamethyltetracosane (C30H62, squalane) with methane and with ethane were measured in optical cells in the temperature range 130 to 550 K and at pressures up to 200 MPa. Methane + squalane exhibits upper critical solution temperatures and pressures and its critical p(T) curve resembles critical gas-gas equilibrium behaviour of the second kind. Ethane + squalane has a complicated phase diagram showing upper critical solution pressures and lower as well as upper critical solution temperatures. The results are discussed from a phase-theoretical and a thermodynamic point of view. © 1979.