| abstract |
A process for the preparation of 4,4'-dinitrostilbene disulfonic acid-2,2 'and / or its salt of the formula shown in the drawing, in which M represents a hydrogen atom or an alkali metal cation, by air oxidation of p-nitrotoluenesulfonic acid-2 in an alkaline medium, optionally in in the presence of a catalyst, characterized in that during the course of the process, the redox potential of the reaction mixture, mixed or mixed with the reference electrode, is kept at a level of not less than minus 300 mV, preferably minus 150 mV. |