Limiting activity coefficient measurements in binary mixtures of dichloromethane and 1-alkanols (C1–C4)

Limiting activity coefficients γ∞ in binary mixtures of dichloromethane with four lower 1-alkanols (C1–C4) were experimentally determined employing alternatively the techniques of inert gas stripping, comparative ebulliometry, Rayleigh distillation, and differential distillation. For each case, the suitable technique was chosen on the basis of the limiting relative volatility of the solute and/or volatility of the solvent. The measurements yielding data of good accuracy (relative standard uncertainty of γ∞ from 0.01 to 0.03) were carried out at several temperatures in the range from (283–333) K. The variation of limiting activity coefficients with temperature was fitted by a suitable two- or three-parameter equation and compared with available literature information on both limiting activity coefficients and calorimetric partial molar excess enthalpies at infinite dilution. The performance of the leading prediction method Modified UNIFAC was further examined using these new data. Concentration dependences of activity coefficients calculated from their infinite dilution values using van Laar equation were found to agree well with those inferred from reliable VLE data from the literature. The occurrence of an azeotropic point was tested for the systems under study and the temperature dependence of the azeotropic composition was estimated for mixtures of dichloromethane with methanol and ethanol.