POTENTIOMETRIC STUDIES ON ELECTRON-TRANSFER REACTIONS OF ANODICALLY GENERATED MANGANESE(III) SULFATE IN AQUEOUS H2SO4-HOAC AND MANGANESE(III) ACETATE IN AQUEOUS ACETIC-ACID - OXIDATION OF SEMICARBAZIDE AND SEMICARBAZONES

Manganese(III) sulphate in aqueous sulphuric acid and manganese(III) a cetate in aqueous acetic acid have been prepared by electrolytic metho ds with high current efficiency. The nature of the manganese(III) form ed is elucidated spectrophotometrically. Condition for potentiometric determination of semicarbazide and its derivatives under different rea ction conditions have been investigated. Hydrazinium sulphate or hydro quinone is employed as back-titrant. The number of electrons in these oxidations differed, depending on the nature of the molecule and tile reaction condition. The free radical nature of the reaction intermedia te is demonstrated. Manganese(III) sulphate and manganese(III) acetate oxidation of semicarbazide and its derivatives in aqueous H2SO4 or aq ueous HOAc yielded different results, probably because of the changes in the coordination environment of manganese(III).