The molecule is an arenesulfonic acid that is 3-[(4-amino-3-methylphenyl)(4-aminophenyl)methylidene]-6-iminocyclohexa-1,4-diene-1-sulfonic acid in which the hydrogens ortho to the amino functions are replaced by phenyl groups. The disodium salt is the biological stain 'acid fuchsin'. It is an arenesulfonic acid, an imine and a primary arylamine. It is a conjugate acid of an acid fuchsin(2-).
3-[bis(4-amino-3-sulfophenyl)methylidene]-6-imino-5-methylcyclohexa-1,4-diene-1-sulfonic acid