CRITICAL LINES FOR TYPE-III AQUEOUS MIXTURES BY GENERALIZED CORRESPONDING-STATES MODELS

An algorithm has been developed for calculating the gas-gas critical l ine of type-III binary fluid mixtures for extended corresponding-state s (ECS) models. The algorithm searches for an extremum in pressure on the spinodal curve of an isothermal pressure-composition phase diagram of a binary mixture. The method has been applied to solutions of carb on dioxide and of nitrogen in water, starting at the water critical po int. Two variants of ECS have been tested for their ability to represe nt reliable PVTx data in the nitrogen-water mixture. It is demonstrate d that in the latter system both ECS variants produce an artifact in t he gas-gas critical line in the range of 0-0.2 mole fraction of nitrog en.