The oxidation of benzidine, o,o′-tolidine and o,o′-dianisidine by manganese dioxide

The oxidation of benzidine, o,o′-tolidine, and o,o′-dianisidine by manganese dioxide was studied in an acidic medium. It has been shown that the studied substances are quantitatively oxidized by the reagent to the corresponding quinonediimines and that this reaction can be utilized for the indirect titrimetric determination of benzidine and o,o′-tolidine, based either on ferrometric titration of unconsumed manganese dioxide or on ascorbinometric titration of the quinonediimine formed.