2 UNIFIED MODELS OF ASSOCIATED SOLUTIONS AND THEIR REPRESENTATION OF EXCESS ENTHALPY AND VAPOR-LIQUID-EQUILIBRIA OF ALCOHOL HYDROCARBON SYSTEMS

A simple modification of the Flory-Huggins theory is proposed in order to generate new models of associated solutions. These models are base d on postulates analogous to those used in the Kretschmer-Wiebe model. Two unified models of associated solutions (UMAS and NUMAS) arise fro m convenient definitions of a correction factor introduced in the Flor y-Huggins theory. Both of these models reproduce the Kretschmer-Wiebe and Mecke-Kempter models as special cases and may give rise to many ot her models. Equations are developed for activities and excess enthalpi es for the two unified models. The ability of UMAS and NUMAS to repres ent vapor-liquid equilibria and excess enthalpies of a number of binar y alcohol-hydrocarbon systems is evaluated through the use of the maxi mum likelihood parameter estimation procedure. Both of these models ap pear to provide a better representation of VLE and h(E) data than any of three local composition models. The analysis of h(E) data provides some definite trends about the behavior of the model parameters with r espect to temperature and size of the alcohol molecule.