The coulometric generation of manganese(II) from a manganese electrode: : The Titration of EDTA

The anodic behavior of a manganese electrode is discussed. Manganese(II) can be generated with greater than 95% current efficiency over a limited current density range in neutral aqueous and methanolic chloride media. The current efficiency for the generation of manganese(II) as a function of current density, supporting electrolyte, solvent, pH, and generation time is given. Electrogenerated manganese(II) is useful in the coulometric titration of 4.460 × 10^-6–2.214 × 10^-5 mol of EDTA in 1.0 M sodium chloride buffered at pH 5.5. The end-point can be detected amperometrically by monitoring the anodic current from the oxidation of manganese(II) at platinum. The titration error is about 1% in replicate determinations. Permanganate can be generated in aqueous sodium hydroxide media but the current efficiencies are less than 20% and irreproducible.