Utilization of solutions after the electroreduction of a sodium salt of 4-nitrosodiphenylamine

An approximately 20-% alkali solution remains after the electroreduction of an alkali solution of a sodium salt of 4-nitrosodiphenylamine (II), in the course of which the formed 4-aminodiphenylamine (I) is continuously extracted into a water-immiscible solvent. The remaining solution, which contains about 10 mM I and up to 1 mM II, may be used for preparing the catholyte for another experiment. To this end, the solution must be anodically treated using a stainless-steel electrode, and the charge spent in the treatment must equal that spent during the electroreduction. After the treatment, the solution settles; the content of II remains virtually unchanged, that of I drops about tenfold, and that of alkali is 50% of the calculated (1 F per mole of alkali). A multiple use of the same alkali solution makes no impact on the yields of I.