Naphthionic acid is an organic compound with the formula C10H6(SO3H)(NH2).

It is a white solid, although commercial samples can appear gray.

Solid Red A), during which the amino group of the acid (in the form of a salt) is diazotated and then coupled with, in the case mentioned, β-naphthol.

It is prepared by treating 1-aminonaphthalene with sulfuric acid.

This article about an aromatic compound is a stub.