Abstract: The invention is concerned with a method of purifying caprolactam as obtained by Beckmann transposition or by nitrosation of cyclohexyl compounds, characterized in that it comprises the following steps:(a) the caprolactam oil is treated with ammonia to obtain a pH in the 8 to 10 range;(b) the caprolactam in water-ammonia solution yielded by (a) is extracted with toluene;(c.sub.1) any caprolactam still in the toluene solution yielded by (b) is treated with NaOH;(C.sub.2) the aqueous phase left over from the extraction with toluene (b) is removed.

Abstract: The invention is concerned with a method of purifying benzoic acid, as obtained by catalytic oxidation of toluene and purification by rectification with the secondary streams being cycled back into the oxidation reactor, characterized in that the secondary streams flowing out of the stripping column undergo the following sequential steps: (a) at least one distillation and at least one crystallization in an organic solvent; (b) scrubbing of the crystals obtained from (a) with the same solvent as in (a); (c) cycling of the mother liquors from crystallization in (a) plus the scrubbing liquors as in (b) back into the dissolver; (d) further scrubbing of the crystals from (b) with the same solvent as in (a) and cycling back of the scrubbing liquors, the crystals scrubbed as in (d) being optionally (d1) further scrubbed with water.