Kv. Narayanan et Ms. Ananth, A MODIFIED SELF-CONSISTENT LOCAL COMPOSITION MODEL FOR THE THERMODYNAMIC PROPERTIES OF SINGLE AND MIXED ELECTROLYTES, Fluid phase equilibria, 114(1-2), 1996, pp. 89-121
In the recently developed self-consistent-local composition (SCLC) the
ory (Ananth and Ramachandran, 1990) the osmotic and activity coefficie
nts in single electrolyte solutions are expressed as sums of several i
ndependent contributions. In the present work, the approximate proport
ionality between certain pairs of these contributions is identified an
d the model is reformulated with fewer and more orthoganal parameters.
The numerical difficulties experienced with the original model in the
evaluation of parameters and in the extension of the calculations to
mixed electrolyte systems are thus eliminated. The simplified model is
shown to correlate the activity and osmotic coefficient data of large
number of single and those of mixed electrolyte systems with good acc
uracy. The osmotic and activity coefficient of single electrolyte solu
tions are expressed in terms of two binary adjustable parameters and m
ixed electrolyte systems containing two salts and one solvent are expr
essed in terms of only one adjustable parameter in addition to the bin
ary parameters determined from the component single electrolyte system
s. The theory contains no additional adjustable parameters in the case
of multielectrolyte (more than two salts) systems. The model is found
to represent satisfactorily the behavior of electrolyte solutions at
different temperatures with a single set of temperature-independent pa
rameters.