Activity coefficients of strong electrolytes in multicomponent aqueous solutions

• Published in: AIChE journal 1972-03, Vol.18 (2), p.294-298
• Main Authors: Meissner, H. P., Kusik, C. L.
• Format: Article
• Language: English
• ISSN: 0001-1541; 1547-5905
• DOI: 10.1002/aic.690180208

The quantity T12 here called the reduced activity coefficient is related to Γ12 the mean activity coefficient of a strong electrolyte 12 as follows: \documentclass{article}\pagestyle{empty}\begin{document}$$\Gamma _{12} = \gamma 12^{{1 \mathord{\left/ {\vphantom {1 {z_1 z_2 }}} \right. \kern-\nulldelimiterspace} {z_1 z_2 }}}$$\end{document} where z1 and z2 are the charge number on the ions. The value of Γ12 for electrolyte 12 in an aqueous solution containing the three ions 1, 2, and 3, such as Na+ Cl− and Ba++, is to be calculated as follows: \documentclass{article}\pagestyle{empty}\begin{document}$${\rm log}\Gamma _{12} = {\rm log}\Gamma ^ \circ _{12} + {\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}\left({{\rm X}_{\rm 3} } \right){\rm log}\left({{{\Gamma ^ \circ _{32} } \mathord{\left/ {\vphantom {{\Gamma ^ \circ _{32} } {\Gamma ^ \circ _{12} }}} \right. \kern-\nulldelimiterspace} {\Gamma ^ \circ _{12} }}} \right)$$\end{document} Here Γ°32 and Γ°12 are for the indicated electrolytes, namely NaCl and BaCl2 in this example, at the total ionic strength of the mixture. The term X3 represents the fraction m3z32/(m1z12 + m3z32) in which m represents the molality of the indicated ion. Fair success is usually attained with this equation in predicting γ, even at high electrolyte concentrations. Similar equations are proposed for aqueous solutions containing four or more ions.