Primuline

Primuline is a dye containing the benzothiazole ring system. Primuline itself is also known as Direct yellow 7, Carnotine, or C.I. 49010.

The primulines are considered derivatives of dehydrothiotoluidine (aminobenzenyltoluylmercaptan), which is obtained when para-toluidine is heated with sulfur for eighteen hours at 180-190 °C and then for a further six hours at 200-220 °C Dehydrothiotoluidine is not itself a dye-stuff, but if the heating is carried out at a higher temperature in the presence of more sulfur, then a base is formed, which gives primuline yellow upon sulfonation.