Prediction of salt effect on vapour-liquid equilibria of alcohol plus alcohol and alcohol plus water binary mixtures

Prediction of isobaric vapour-liquid equilibria (VLE) of solvent (1) + solvent (2) + salt (3) ternary systems is carried out with a semi-empirical model proposed by Hala. The value of the exponent beta in Hala's equation is treated as a fixed common value defined by the kind of salt (CaCl2, NaI, and NH4I). The beta values are determined by isothermal VLE data of fifteen ternary systems containing salt. Other constants in the Hala equation are also determined from the data of VLE and vapour pressure of three binary mixtures, constructing a ternary system. Isobaric VLE of five ternary systems are predicted within the average deviation of +/-4.2% in vapour phase composition and +/-1.0% in temperature. The linear relationship between the ratio of the short-range interaction constant of the Wilson parameter [1n (Lambda(23)/Lambda(13))] and the relative volatility ratio [In (alpha(s)/alpha)] of a binary mixture containing salt are observed; the relationship is independent of the kind of salt.