The present invention relates to a method for treating a substance mixture comprising an aromatic amine, wherein the aromatic amine is aniline or 2,4-diaminotoluene, preferably aniline. The substance mixture comprises an aromatic amine and compounds having a higher boiling point than the aromatic amine. The method for treating the substance mixture requires I) separating the first substance mixture by means of distillation in a first distillation unit (110, 1130), to at least partially remove some of the aromatic amine in the process, and to obtain a first bottom product which is removed from the first distillation unit (110, 1130). After removal from the first distillation unit (110, 1130), the bottom product is diluted with a condensed top product from a distillation unit that is different from the first distillation unit and/or with a composition that comprises methanol.