Journal of Solution Chemistry, Vol. 24, No. 3, 1995 Preferential Solvation In Three Component Systems: Evaluation of Kirkwood-Buff Parameters Debashis Banerjee, 1 Ashis Kumar Laha/ Prasanta Chatterjee, 1 and Sanjib Bagchi 1. Received September 30, 1992; Revised March 3, 1994 The extent of local excess or deficiency of a component solvent near the solute ~Sl in a mixed binary solvent has been calculated using the Hail for- malism for the Kirkwood-Buff equation. The possibility of calculation of the two solute-solvent Kirkwood-Buff parameters Gsi using the ~sl values is discussed. A model calculation using literature data for preferential sol- vation in mixed binary solvents is presented. The solute-solvent and solvent-solvent interactions and the relative s&e of the solvents are also shown to be relevant factors in determining the Gsl values. KEY WORDS: Preferential soIvation; Kirkwood-Buff parameters; solute-solvent interactions. 1. INTRODUCTION The problem of solvation of a solute in a mixed binary solvent is a matter of current interest both from the experimental and theoretical point of view. (~5) The solvent composition that the solute sees in its im- mediate vicinity may in general be different from the bulk composition of the mixed solvent. This phenomenon, commonly known as preferen- tial solvation (PS) of the solute, has been found to have great practical importance. (6) Experimentally the extent of PS may be determined by following a suitable solvent sensitive physico-chemical property of the solute as a function of the composition of the mixed solvent. (2'~-14)At the molecular level the distribution of the solvents around the solute is described by a radial distribution function. It has been found that Department of Chemistry, Umvermty of Burdwan, tlurdwan 713 104, India. 301 0095-9782/95/0300-0301507.50/0 9 1995Plenum PublishingCorporation