An analysis of the thermodynamics of transfer of polar non-electrolytes from water to aqueous concentrated salt solutions

Abstract

A calorimeter has been constructed and used to determine the limiting enthalpies of solution (ΔH_S) of a series of alkyl acetates (methyl, ethyl, propyl, butyl and t-butyl) in water and aqueous solutions of some of the following salts: LiCl, NaCl, KCl, CsCl, KF, KBr, NaNO₃ and NaClO₄. These measurements are combined with previous activity coefficient determinations to obtain the thermodynamics of transfer for the esters. In the case of transfer to NaCl solutions, scaled-particle theory calculations are used to determine the thermodynamics of cavity transfer, which, when combined with the experimental total-transfer quantities, give rise to a set of quantities that we have called the interaction transfer quantities. These quantities indicate that the predominant factors in the transfer of neutral molecules containing both polar and non-polar segments from water to NaCl solutions are the transfer of the cavity and of the interactions of the polar group. The interactions of the alkyl side chains are shown to be similar to those of alkane molecules.