| abstract |
The present invention relates to a special procedure for carrying out the nitration of naphthalene-1,3,6-trisulfonic acid to 8 nitronaphthalene-1,3,6-trisulfonic acid, which is characterized in that at least 80% of the fully reacted nitrating mixture is initially charged Nitriding material dissolved in sulfuric acid and simultaneously adding nitric acid in such a way that during the nitration the sulfuric acid concentration is maintained in the range 86 to 94%, the reaction mixture is mixed well and the reaction temperature is kept in the range 30 to 60 ° C. |