Supporting Electrolyte Influences upon Half-Wave Potentials in Acetic Acid-Acetic Anhydride

Abstract

Th,e half-wave potentials for the reduction of metallic ions at the dropping mercury electrode in nonaqueous solvents are highly sensitive to changes in the solvent and the electrolytic environment. The variables influencing the half-wave potentials that have been summarized by Coetzee, et al. (4) are: (a) the association by electroactive iorns and those of the suppo'rting electrolyte into, ion pairs and higher aggregatets; (b) the activity coefiicients for all electrolytic species in the solution; (c) complex ion formation involving electroactive ions with ligands other than the solvent; and (d) the free energy of solvation for electroactive ions. Of these, the first three influences have thle greatest dependence upon the supporting electrolyte and its activity in solution. Very few investigations have been made on th,e polarography of metallic ions in glacial or anhydrous acetic acid (1, 2, 8, 15). However, it is the purpose of this no,te to assess the role of the supporting telectrolyte in acetic acid media from the recently reported data obtained by Headridge and Pletcher (8) for acetic acid containing 1:20 (v/v) acetic anhydride.