454 Professor Sir Henry E. Roscoe [April 16, 



by fractional distillation. On the ITth of February, 1856, Mansfield 

 was occupied with the distillation of this hydrocarbon, which he 

 foresaw would find further aj^plications, for the Paris Exhibition, in 

 a still. The liquid in the retort boiled over and took fire, burning 

 Mansfield so severely that he died in a few days. 



The next step in the production of colours from benzene and 

 toluene is the manufactui'e of nitrobenzene, CgHsNOa and nitrotoluene, 

 C7H7NO2. The former compound, discovered in 1834 by Mitscherlich, 

 was first introduced as a technical product by Collas under the name 

 of artificial oil of bitter almonds, and Mansfield in 1847 patented a 

 process for its manufacture. It is now used for perfuming soap, but 

 mainly for the manufacture of aniline (CgHgNlIa) for aniline blue 

 and aniline black and for magenta. It is made on a very large scale 

 by allowing a mixture of well-cooled fuming nitric acid and strong 

 sulphuric acid to run into benzene contained in cast-iron vessels pro- 

 vided with stirrers. 



To prepare aniline from nitrobenzene, this compound is acted 

 upon with a mixture of iron turnings and hydrochloric acid in a 

 cast-iron vessel. Commercial aniline is a mixture of this compound 

 with toluidine obtained from toluene contained in commercial benzene. 

 Some idea of the magnitude of this industry may be gained from the 

 fact that in one aniline works near Manchester no less than 500 tons 

 of this material are manufactured annually. From the year 1857, 

 after Perkin's celebrated discovery * of the aniline colours, up to the 

 present day, the history of the chemistry of the tar products has been 

 that of a continued series of victories, each one more remarkable than 

 the last. 



Coal-tar Colours. — To even enumerate the difierent chemical com- 

 pounds which have been prepared during the last thirty years from 

 coal-tar would be a serious task, whilst to explain their constitution and 

 to exhibit the endless variety of their coloured derivatives which are 

 now manufactured would occupy far more time than is placed at my 

 disposal. Of the industrial importance of these discoveries, the 

 speaker reminded his audience of the wonderful potency of chemical 

 research, as shown by the fact that the greasy material which in 1869 

 was burnt in the furnaces or sold as a cheap waggon grease at the rate 

 of a few shillings a ton, received two years afterwards, when pressed 

 into cakes, a price of no less than one shilling per pound, and this 

 revolution was caused by Grabe and Liebermann's synthesis of 

 alizarin, the colouring matter of madder,| which is now manufactured 



* See Lectures by Professor Hofmann, F.E.S., 'On Mauve and Magenta,' 

 April 11, 1862, and W. H. Perkin, F.R.S., 'On the Newest Colouring Matters,' 

 May 14, 1869, Proc. Roy. Inst. ; also President's Address (Dr. Perkin, F.R.S.), 

 ' Journal of Society of Chemical Industry,' Vol. IV., July 1884, on Coal Tar 

 Colours. 



t ' On the Artificial Production of Alizarine, the Colouring Matter of 

 Madder,' by Prof. H. E. Roscoe, Proc. Roy. Inst., April 1, 1870 ; also Dr. Peildn, 

 F.R.S., ' On the History of Alizarine,' Journal Society of Arts, May 30, 1879. 



