Helgeson-Kirkham-Flowers correlation

Some fairly well-validated estimation techniqnes exist for the standard-state properties of electrolytes in water. The one in widest nse is the Helgeson-Kirkham-Flowers (HKF) correlation, as implemented in software known as SUPCRT92. Versions of the software may be fonnd with a Web search, and a site [77] provides access to the most cnrrent set of parameters. 

More recently, Brossia et al. [35] introduced an approach based on new correlations for activity coefficients in concentrated solutions. This proach [101] is based on the Helgeson-Kirkham-Flowers equation for standard-state properties with a nonideal solution model based on the activity coefficient expression developed by Bromley and Pitzer. Using specific software, Brossia et al. were able to predict the dominant ionic species and the salt precipitation in Ni, Fe, Cr, and 308 stainless steels crevice solutions. Fair agreement was observed with the in situ analyses of these crevice solutions by Raman spectroscopy. 

Some other kinds of models have shown parameters that seem to follow useful correlation relationships. Among these are the virial coefficient model of Bums (2), the interaction coefficient model of Helgeson, Kirkham, and Flowers (4), and the hydration theory model of Stokes and Robinson (1). The problem shared by all three of these models is that they employ individual ion size parameters in the Debye-Hiickel submodel. This led to restricted applicability to solutions of pure aqueous electrolytes, or thermodynamic inconsistencies in applications to electrolyte mixtures. Wolery and Jackson (in prep.) discuss empirical modification of the Debye-Huckel model to allow ion-size mixing without introducing thermodynamic inconsistencies. It appears worthwhile to examine what might be gained by modifying these other models. This paper looks at the hydration tlieory approach. 

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See also in sourсe #XX -- [ ]

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