Description of electrolytes at high temperatures within the binding mean spherical approximation (BiMSA).

In this work, the binding mean spherical approximation (BiMSA) theory is used to describe osmotic and activities coefficients for electrolytes solutions up to high temperatures. Four salts are analysed: NaCl, LiCl, $ {\rm MgCl}_2 $ MgCl 2 and $ {\rm CaCl}_2 $ CaCl 2 , in the temperature range of 25 $ ^{\circ } $ ∘ C to 300 $ ^{\circ } $ ∘ C and molalities from 0.05 to 6 molal. A good representation of experimental data is obtained for all salts and temperatures considered by introducing temperature-dependent cation size and permittivity in a suitable way. The proportion of ion pairs (that are formed at sufficiently high temperature in these solutions) for each salt is predicted from the theory, showing a pronounced increase for temperatures above 100 $ ^{\circ } $ ∘ C. A good agreement is found between the values of optimised and experimental association constants given in the literature. [ABSTRACT FROM AUTHOR]