T h e perturbed anisotropic chain theory (PACT) d e v e l o p e d b y Vimalc h a n d a n d Donohue h a s b e e n generalized t o t r e a t pure fluids t h a t assoc i a t e through hydrogen bonding, as well as mixtures of one a s s o c i a t i n g component a n d several diluents. Using an a p p r o a c h similar t o t h a t of Heidernann a n d Prausnitz, a closed-form equation of s t a t e h a s b e e n derived. It is applicable t o simple as well as complex molecules at both gas a n d liquidlike d e n s i t i e s and t a k e s into account dipole and/or quadrupole moments. Molecular p a r a m e t e r s were obtained by fitting t h e equation t o experimental liquid density a n d vapor p r e s s u r e d a t a .

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The associated perturbed-anisotropic-chain theory (APACT) has been applied to treat multicomponent mixtures, in which components exhibit Lewis acid-base interactions. Mixtures of amphoteric molecules (such as alcohols), acidic molecules (such as chloroform), and basic molecules (such as ketones) as well as nonassociating components (diluents) are treated. The acid-base version of the perturbedanisotropic-chain theory (ABPACT) is a closed form equation of state that takes into account explicitly dispersion interactions, polar interactions, and hydrogen bonding interactions between components that self-associate or solvate. The equation fits binary VLE mixtures quite accurately. Calculated results also are compared with those obtained from the Peng-Robinson equation of state, UNIFAC and the original APACT. In all cases where there are mixtures of associating components, the ABPACT gives a better fit of experimental data than these other equations.

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