1911 Encyclopædia Britannica/Primuline

PRIMULINE, a dye-stuff containing the thiazole ring system conjointly with a benzene ring.

CH3		S	C·C6H4·NH2(p)
		N
Primuline.

The primulines are to be considered as derivatives of dehydrothiotoluidine (aminobenzenyltoluylmercaptan), which is obtained when para-toluidine is heated with sulphur for eighteen hours at 180–190° C. and then for a further six hours at 200–220° C. (P. Jacobson, Ber., 1889, 22, p. 333; L. Gatterrnann, ibid. p. 1084). Dehydrothiotoluidine is not itself a dye-stud, 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, 1, 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)]. Thioiflavine 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.