POTENTIAL OF COUPLE MN(3)-MN(2) IN AQUEOUS 3-M-HCLO4

The redox equilibria between Mn2+ and manganese species in a higher oxidation state Mnqp+, with p/l +2, have been studied at 25 °C by electrooxidizing acid manganese(II) perchlorate solutions at a gold gauze anode. In the freshly oxidized solutions the potential acquired by gold electrodes against a hydrogen half-cell as well as the number of moles of Fe2+ oxidized by one liter of solution were measured. The total managanese concentration ranged from 0·01 to 0·1 M, and the solutions were prepared to contain 3 M ClO4- by adding HClO4. The potential measurements, combined with the analytical data, can be explained by assuming the formation of Mn3+ species only. In the ionic medium 3 M CHlO4 the standard potential has been determined. Mn3++e-⇆Mn2+,e2,31541·5±0·3mV. © 1969.