Effect of a salt on the kinetics of solute transfer at a free liquid/liquid interface

The effect of a salt on the kinetics of transfer of acetic acid at a free l iquid/liquid boundary has been studied using the rotating membrane cell tec hnique. LiCl, NaCl or KCl, at concentrations between 0 and 8 mol L-1, have been added to the aqueous phase. The organic phase was composed of a pure l iquid: isopropylmyristate (isopropyltetradecanate). This type of system is interesting because it leads to a "simple" interfacial transfer process, co nsisting only of a change of solvation. The kinetic rate of transfer has be en measured as a function of the salt concentration. The activity coefficie nt of the acetic acid in the aqueous phase containing salt has been determi ned experimentally by solvent partitioning. In contradiction with an often- made assumption, it has been found that this quantity is not sufficient for describing the effect of a salt on the kinetics of transfer of acetic acid . Specific effects occurring at the interface are expected to play an impor tant role.