THERMODYNAMIC CONSISTENCY, TESTS BASED ON THE GIBBS-DUHEM EQUATION APPLIED TO ISOTHERMAL, BINARY VAPOR-LIQUID-EQUILIBRIUM DATA - DATA EVALUATION AND MODEL TESTING

Four thermodynamic consistency tests are discussed along with sufficie nt background information so that approximations to these otherwise ri gorous tests are fully appreciated. The tests are applied to three bin ary systems, one at low pressures, one at moderate pressures and the l ast at high pressures. The results provide information on the data and the models used to fit them. These results are highly sensitive to th e selection of the models, a conclusion worth noting for those selecti ng physical property models in process simulators and performing PTx e xperiments. For example, the choice of an inappropriate equation of st ate for the representation of vapor-phase properties will introduce th ermodynamic inconsistencies that cannot be removed by simply increasin g the number of adjustable parameters in the activity coefficient expr essions.