1-Aminonaphthalene-3,7-disulfonic acid [6362-05-6]. (4-aminonaphthalene-2,6- disulfonic acid), Freund’s acid(1,3,7), C10H9NO6S2, Mr 303.3, is readily soluble in water, but its salts are less soluble than those of the 1,3,6-isomer. The amino group is hydrolyzed by water at 180℃ to give 1-hydroxynaphthalene-3,7-disulfonic acid. Caustic fusion results in formation of 1-amino-7-hydroxynaphthalene-3- sulfonic acid, and amination gives 1,3-diaminonaphthalene-7-sulfonic acid.
The 1,3,7-acid is produced together with the 1,3,6-isomer.
