ChEBI: Primuline (acid form) is a member of the class of benzothiazoles that is 2,6'-bi-1,3-benzothiazole substituted at positions 2' 6 and 7 by 4-aminophenyl, methyl and sulfo groups respectively. The monosodium salt is the biological dye 'primuline'. It has a role as a fluorochrome and a histological dye. It is a member of benzothiazoles, a ring assembly, a substituted aniline and an arenesulfonic acid. It is a conjugate acid of a 2'-(4-aminophenyl)-6-methyl[2,6'-bi-1,3-benzothiazole]-7-sulfonate.