114 [Proc. B. N. F. C, 



were termed, from the battles fought about the time of its dis- 

 covery. These were, I think, the only aniline colours in exis- 

 tence when our Club was formed. Since then we have had the 

 discovery of Hoifman's violet, the aniline green, and Nichol- 

 son's golden yellow hue, Phosphine, the latter obtained from a 

 residuum or bye-product in the manufacture of magenta. 

 Again, when carbolic acid, obtained by the distillation of tar, is 

 treated with nitric acid, picric acid is obtained, which in solu- 

 tion imparts a bright, pure yellow dye. Strange to say, this 

 yellow colouring matter, when treated with cyanide of potas- 

 sium, gives a rich purple dye, identical with the famous Tyrian 

 purple. With every varying change of fashion, new shades of 

 colour are introduced from coal tar products, and at such 

 cheap rates as the natural and original sources cannot possibly 

 compete with. 



One of the peculiarities of some of these colouring matters is 

 their extreme diffusibility. It is stated that one ten-millionth 

 of a grain of magenta will give its colour to a drop of water. 

 Not only do we find these substances used for dyeing and 

 printing textile fabrics, but they enter into the composition of 

 our printing and writing inks, and give the colour for rubber 

 stamp pigments, while the diffusibility of the purples and reds 

 enables us to multiply copies of writing by the various cento- 

 graph and hectograph processes. The most interesting feature, 

 however, from a natural history point of view, in connection 

 with these coal tar products, has been the synthetic production 

 of Alizarine, which is identical with the colouring matter 

 obtained from the madder root. In the earlier days of 

 chemistry, it was considered that while the chemist, having 

 determined upon the constituents of an inorganic body, could 

 in many instances form it in his laboratory, the formation of 

 organic substances was quite beyond his power, and that they 

 could only be produced in the living bodies of animals or 

 plants, requiring a vital force for their construction. So far 

 back as 1828, Wohler succeeded in producing Urea syntheti- 

 cally, and some seventeen years after, Kolbe accomplished the 



