THE COAL-TAR INDUSTRY IN ENGLAND AND GERMANY. 255 



colours. The closer investigation of the thiazol group, to which primuline 

 belongs, further led to the discovery of many other cotton colours 

 belonging to this family, amongst the most important of which are the 

 brilliant greenish-yellow called ' Turmerine ' or ' Clayton Yellow,' the 

 light-fast ' Chlorophenine ' or ' Chloramine Yellow,' the pure greenish 

 basic yellow ' ThioHavine,' and the fast cotton pink ' Erica.' 



Passing over the stilbene azo colours and the basic azo ammonium or 

 ' Janus ' colours there remains a class of azo compounds to which I must 

 shortly refer, namely, the mordant azo colours, which with the growing 

 demand for faster shades have recently come into much prominence. In 

 these compounds the presence of an ortho hydroxyl or carboxyl group 

 gives to the colour the property (following Liebermann and v. Kosta- 

 necki's rule) of combining with metallic mordants, especially chromium 

 oxide, and producing therewith insoluble and fast lakes on the wool or 

 cotton fibre. 



We now come to the consideration of three analogously constituted 

 groups of colouring matters, namely, the azines, oxazines, and thiazines. 

 The laborious scientific investigations of Fischer and Hepp, Bernthsen, 

 Kehrmann, and others on the constitution of these groups of compounds, 

 the tirst members of which (Methylene Blue, Saffranine, and Meldola's 

 Blue) were discovered in a very early stage of the industry when little 

 or nothing was known of their structure, combined with the theoretical 

 views on the quinonoid structure of such colouring matters promulgated 

 by Armstrong and adopted by Nietzki, led to the discovery of many 

 valuable new members of these classes. Amongst the latter may be 

 specially mentioned the Rosindulines, Indoine Blue, Induline Scarlet, 

 Rhodulines, &c. 



Passing to the pyrone and acridine groups in which much investiga- 

 tion has also been conducted, the most notable advances have been the 

 discovery of the ' Rhodamines,' a class of pure basic reds, and of the basic 

 yellows and oranges allied to Phosphine, namely Acridine Yellow, Benzo- 

 flavine, and Acridine Orange. 



It is in the alizarine group next to the azo group that the greatest 

 progress must be recorded. The demand for fast colours for calico 

 printing and for dyeing chrome-mordanted wool to withstand severe 

 ' milling ' operations has led to a long series of investigations and patents 

 for producing new derivatives of anthraquinone. These new products, 

 known in commerce as ' Alizarine Bordeaux,' ' Alizarine Cyanines,' 

 ' Anthracene Blues,' ' Alizarine Viridine,' ' Alizarine Saphirol,' &c., are 

 polyoxy- or amidooxy-anthraquinones, for the preparation of which 

 either alizarine or nitroanthraquinones are the i;sual starting points. 



Passing over some smaller groups, we now come to a very peculiar 

 class of dyestuffs containing sulphur, which, although discovered by 

 Croissant and Brettoniere in 1873, remained confined to a single repre- 

 sentative — ' Cachou de Laval ' — until Raymond Vidal in 1893 obtained a 

 very fast black colouring matter, which dyed unmordanted cotton, by 

 heating paraamidophenol with sulphur and sodium sulphide. The 

 possibility of replacing Aniline Black in cotton dyeing by a direct 

 colouring matter, and possibly also of obtaining other shades which, though 

 dyed in a single bath, would resist subsequent ' cross dyeing ' of the 

 wool in "mixed fabrics, lent an immense impulse to the study of this class 

 oiE colouring matters ; and although their molecular structure still remains 

 wrapped in obscurity, many new repre'sentiative's have followed ea'ch 



