86-66-8

The total reaction mixture is nitrated, and the resulting 8-nitro derivative is reduced to give 1-aminonaphthalene-3,6,8-trisulfonic acid (Koch acid), the key intermediate in the production of the important H acid. The crude trisodium salt may be precipitated from the quenched mixture after dilution to 75 % acid strength to give a product (Azoguard) used as a diazo stabilizer.

ChEBI: Naphthalene-1,3,6-trisulfonic acid is a naphthalenesulfonic acid.

Naphthalene is initially sulfonated with sulfuric acid monohydrate under programmed temperature control between 80 and 145℃. Then, 65 % oleum is added gradually at 40℃ and heating is continued for 2.5 h at 145℃. Trisulfonation is complete after the further addition of 65 % oleum and heating for 3 h at 150℃. This complex procedure maximizes the formation of Naphtalene-1,3,6-trisulfonic Acid with a conversion of up to 75 %.