- Synonyms: 1-(p-Phenylazophenylazo)-2-naphthol, Sudan red BK - C22H16N4O - M = 352,40 g/mol - CAS [85-86-9] - EINECS-No.: 201-638-4 - Tariff number: 3204 19 00 90 - Applications: microscopy, bacterium staining. SPECIFICATIONS suitability for microscopy: passes test