Prediction of stability limits and critical conditions of binary liquid mixtures containing nitro-methane using the NRTL model

The stability limit (spinodal) curves and critical points for binary liquid solutions of nitro-methane with 21 different compounds are determined by employing the rigorous stability and criticality thermodynamic criteria using the NRTL model. The NRTL binary interaction parameters used are those resulting from the regression of the available experimental binodal data in the literature. All systems considered in this work show upper critical solution temperatures (UCST) with a very clear convergence of both the spinodal and the binodal curves at the mixture critical point. The predicted mixture critical temperatures, together with the available binodal data were tested for compliance with the universal criticality theory, which implies that as a certain “field variable” (e.g., T − Tc) approaches the critical value the behaviour of “order parameters” (such as ρL − ρG) follow a simple power law with universal exponents. The predicted critical exponents for two order parameters of relevance to the liquid–liquid systems, that is the difference in mole fraction of species 1 in the two coexisting phases x ′ 1 − x ″ 1 and the susceptibility (χ), which is related to the chemical potential of species 1 were found consistent with those reported in the literature from other order parameters like magnetization and density difference.