PRIMULINE  , a dye-stuff containing the thiazole

ring system conjointly with a benzene ring . The primulines are to be considered as derivatives of dehydrothiotoluidine (aminobenzenyltoluylmercaptan), which is obtained when para-tolui- S\ CH „/\/ •CBH4.NH,(p) \/\N/ Primuline . dine is heated with sulphur for eighteen hours at 18o–xgo C. and then for a further six hours at 200–2200 C . (P . Jacobson, Ber., 1889, 22, p . 333; L . Gattermann, ibid. p . 1084) . Dehydrothiotoluidine is not itself a dye-stuff, but if the heating be carried out at a higher temperature in the presence of more sulphur, then a base is formed, which gives primuline yellow on sulphonation (A . G . Green, Journ . Soc .

Chem . Ind., 1888, r, p . 194) . Primuline-yellow is a mixture of

sodium salts and probably contains in the molecule at least three thiazole rings in combination . It is a substantive cotton dye of rather fugitive shade, but can be diazotized on the fibre and then developed with other components, so yielding a series of ingrain colours . Thioflavine T is obtained by the methylation of dehydrothiotoluidine with methyl alcohol in the presence of hydrochloric acid [German Patent 51738 (1888)] . Thioflavine S results from the methylation of dehydrothiotoluidine sulphonic acid . This sulphonic acid on oxidation with bleaching powder or with lead peroxide, in alkaline solution yields chloramine yellow, which dyes cotton a beautiful yellow .