Normalization of Potentials in Propylene Carbonate, Ethylene Carbonate, <i>N</i>,<i>N</i>′-Dimethylformamide, and Dimethyl Sulfoxide to the Water Scale Studied by Polarographic Method

Abstract

Abstract The polarographic behavior of alkali metal ions were studied in propylene carbonate (PC), ethylene carbonate (EC), water, N,N′-dimethylformamide(DMF), and dimethyl sulfoxide(DMSO). The polarographic half-wave potentials measured in these solvents against an aqueous saturated calomel electrode(SCE) were normalized to the potential of SCE in aqueous system by making corrections of potential required for transfer of rubidium ion from water to these solvents. The free energies of transfer of rubidium ion from water to other solvents were calculated by the application of the modified Born equation. The potential series on the normalized potential scale were given in the order DMSO&amp;lt;DMF&amp;lt;water&amp;lt;PC&amp;lt;EC, indicating that the metal ion-solvent interaction increases with increasing the electron donor property of the solvent. The solvent shifts in potential calculated by the application of the modified Born equation disagreed with the experimental results. In order to fit well the calculated solvent shifts in potential with the experimental results, following values of liquid junction potential must be assumed for these solvents; +0.090 V for DMSO, +0.085 V for DMF, +0.004 V for PC, and −0.064 V for EC against the aqueous phase.