The Bromley equation was developed in 1973 by Leroy A. Bromley[1] with the objective of calculating activity coefficients for aqueous electrolyte solutions whose concentrations are above the range of validity of the Debye–Hückel equation.
This equation, together with Specific ion interaction theory (SIT) and Pitzer equations[2] is important for the understanding of the behaviour of ions dissolved in natural waters such as rivers, lakes and sea-water.
[3][4][5] Guggenheim had proposed an extension of the Debye-Hückel equation which is the basis of SIT theory.
He noted that the equation gave satisfactory agreement with experimental data up to ionic strength of 6 molal, though with decreasing precision when extrapolating to very high ionic strength.
As with other equations, it is not satisfactory when there is ion association as, for example, with divalent metal sulfates.
[7] In a comparison of Bromley, SIT and Pitzer models, little difference was found in the quality of fit.
Whilst the Bromley and SIT approaches are based on pair-wise interactions between oppositely charged ions, the Pitzer approach also allows for interactions between three ions.
These equations are important for the understanding of the behaviour of ions in natural waters such as rivers, lakes and sea-water.
For some complex electrolytes, Ge et al.[12] obtained the new set of Bromley parameters using up-to-date measured or critically reviewed osmotic coefficient or activity coefficient data.