GREY POWDER. 1-Amino-8-hydroxynaphthalene-4-sulfonic acid [83-64-7]. (4-amino-5-hydroxynaphthalene-1-sulfonic acid), S acid, C10H9NO4S, Mr 239.2, is only sparingly soluble in hot water. Reaction with bisulfite gives 4,5-dihydroxynaphthalene-1-sulfonic acid. Diazo compounds couple under acid conditions a to the amino group and under alkaline conditions a to the hydroxy group; bisazo derivatives can be obtained.
The S acid and its acetyl derivative are used as azo coupling components in e.g., C.I. Mordant Green 14, C.I. Mordant Blue 7, and C.I. Direct Green 39.
