Application of Kirkwood-Buff theory of liquid mixtures to binary aqueous solutions of alcohols

Abstract

The various integrals over the pair correlation functions, G_AA, G_ww and G_AW (A=alcohol, W= water) have been calculated for aqueous solutions of methanol, ethanol, 1-propanol and tertbutanol at 25°C by utilizing the thermodynamic properties like the isothermal compressibility, partial molar volumes and vapour pressure and by the application of an inverse procedure for KirkwoodBuff theory of solutions as suggested by Ben-Nairn. It is observed that as a function of concentration, G_AA, G_AW and G_ww have extremas in the studied concentration range. The results are compared with similar systems reported earlier and are interpreted on the basis of solvent structural effects and hydrophobic interaction amongst the solute molecules. The behaviour of GAA in dilute concentration indicates that the strength of hydrophobic interaction decreases initially in all the studied water-alcohol systems. The mean square concentration fluctuation parameter N < (<img src='/image/spc_char/delta.gif' border=0>x)² > as a function of concentration has been estimated using G_ij values. These results are in agreement with the available scattering data, suggesting further that the main effect of alcohol is to interfere destructively with low density domains in water in dilute concentration of alcohols in water.