I 



Coal-tar Products. 217 



lOJ or 11 gallons. It is a black, more or less viscid fluid, of 

 spe'cific gravity between 11 and 12. Before proceeding to de- 

 scribe the treatment which it undergoes at the tar distillers, I 

 should like to give you a short chronological history of it and its 

 principal derivatives, which will, I think, afford a very striking 

 proof of the rapid strides which have been made in chemical 

 research during the past fifty or sixty years. 



No doubt, from the first, coal-tar has been used in small 

 quantities as a cheap sort of paint, and towards the end of the 

 last century Lebon, in France, pointed out the use of certain 

 products obtained in the distillation of coal for the preservation 

 of timber. In Germany also, after being boiled down and 

 deprived of its volatile constituents, tar was used for_ making 

 roofing felt. A further step was made towards making it a 

 marketable commodity when the naphthas or light oils produced 

 in the boiling of tar were used in dissolving the india-rubber 

 which was being brought into use by Mackintosh in the manu- 

 facture of waterproof garments. 



In 1820, Garden found in the tar oils a substance known as 

 Naphthalene, which though thus one of the earliest products to 

 be discovered, was one of the latest to be utilised. 



In 1825, Prof. Faraday discovered Benzol, in oils produced 

 by compressing oil-gas ; and in 1832, Dumas and Laurent dis- 

 covered Anthracene, or " Paro Naphthaline" as it was called ; 

 and the same year saw the production by Eeichenbach of 

 Ceeosote from wood-tar. Two years later Runge brought to 

 light Carbolic Acm, or Phenol ; and about the same time he 

 proved the existence of Aniline (or Kyanol as he called it) in 

 coal-tar. — I should say that Aniline (called Crystalline by the 

 discoverer) was obtained in 1826, by Unverdorben, while dis- 

 tilling indigo. — The same chemist (Runge) was the producer of 

 the first colour reaction, and in rather a strange way. He was 

 engaged distilling some tar, and wishing to see whether the oils 

 he had obtained contained ammonia, he dipped a strip of wood 

 into some hydrochloric acid and held it above the stiU ; the 

 white fumes indicative of the presence of ammonia showed 

 themselves, but he was surprised to see also, that the part of the 

 wood which had been dipped in the HCl was dyed a deep 

 crimson. He at once saw that he had found out some new sub- 

 stance, and he gave it the name of " pyrroL" He and others 

 made many attempts to isolate it, but it was reserved for the 

 present Prof. Greville Williams to achieve success. Pyrrol, bow- 

 ever, still remains nothing but a chemical curiosity. Soon after 

 this, viz., in 1837, Pelletier and Walter, by the production 

 of Toluene, made a discovery almost equal in value to that 

 of Benzene. In 1838, a great impetus to the employment of 

 coal-tar was given by the invention by Bethell of a method for 



