131-27-1

2-Aminonaphthalene-4,8-disulfonic acid [131-27-1]. (3-aminonaphthalene-1,5-disulfonic acid), Cassella acid, C acid, C10H9NO6S2, Mr 303.32, and its salts are readily soluble in water. Reduction with sodium amalgam desulfonates 2-Aminonaphthalene-4,8-disulfonic acid to give 2-aminonaphthalene-8-sulfonic acid, whereas boiling with dilute sulfuric acid results in desulfonation and hydrolysis to give 2- hydroxynaphthalene-4-sulfonic acid. Alkali fusion (KOH, 215℃) produces 2-amino-4-hydroxynaphthalene-8-sulfonic acid.

2-Amino-4,8-naphthalenedisulfonic Acid is used in green preparation method of direct blended blue D 3GL.

Cassella acid is an important diazo component for yellow direct and reactive dyes.

The iron(II) salt of 3-nitronaphthalene-1,5-disulfonic acid (nitro-Armstrong acid) is reduced with iron in dilute acid. A claimed improvement involves isolation of nitro-Armstrong acid from the nitration products of naphthalene-1,5-disulfonic acid as the crystalline magnesium salt prior to catalytic reduction to C acid.