A generalized method for thermodynamic consistency test to binary - isothermal or isobaric - vapor-liquid equilibrium data, based on the isothermal method of Van Ness is proposed. The essential step of the method is to solve the coexistence equation (deduced from the Gibbs-Duhem equation) considering the non--ideality of the vapor phase and possibly the heat of mixing data for the specific system. To calculate the t(x) or P(x) function at equidistant points a cubic spline-polynomial is used rejecting Van Ness' equadratic conditions at the two edges. An algorithm using non-equidistant step sizes - thus without curve fitting - was developed and was applied to systems with complete and limited miscibility as well. The test criteria to be applied to residuals are established on a strict mathematical statistical basis.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry