1863.] 647 



that Mr. Church has separated from coal-tar naphtha a hydrocarbon 

 isomeric with benzol, parabenzol, which boils at 97'5. This sub- 

 stance is readily converted into a nitro- compound, and ultimately 

 into the corresponding base. Is it the base thus formed which gives 

 rise to the formation of aniline-red ? 



Or is it not more probable that commercial aniline contains 

 another base analogous or homologous with aniline which is involved 

 in the generation of the red ? 



These are questions equally interesting for theory and practice, 

 and the solution of which will probably throw considerable light upon 

 the still enigmatical genesis of rosaniline. 



VIII. " Contributions towards the History of the Colouring 

 Matters derived from Coal-tar." By A. W. HOFMANN, 

 LL.D., F.R.S. Received June 9, 1863. 



In a previous Note I have shown that the red colouring matter can- 

 not be obtained from normal aniline by the action of the agents 

 usually employed for the preparation of this colour on a large scale. 

 This observation naturally induced me to seek for the constituent in 

 the commercial aniline which gives rise to the formation of aniline-red. 



I have already remarked that the commercial product which is 

 best suited for the manufacture of the red colour, boils at a tempera- 

 ture appreciably higher than the boiling-point of normal aniline. 

 The idea presented itself of submitting this substance to a fractional 

 distillation, or else of effecting a methodical separation of the hydro- 

 carbons which constitute the starting-point for the manufacture of 

 the bases ; but, as is well known, these processes are difficult and 

 tedious, and there is little chance of success unless the operation 

 be performed on a very large scale. 



In the hope of accelerating the inquiry, I examined the action of 

 mercuric and stannic chlorides upon the homologues of aniline, of 

 which I fortunately possessed some pure specimens. The contiguous 

 term toluidine was the first to fix my attention. The presence of this 

 base in commercial aniline could not be doubted, since the benzol 

 employed in the manufacture of this substance almost invariably boils 

 at temperatures between 80 and 100, or even higher. Indeed 

 Mr. Nicholson having convinced himself that pure aniline is not 



2 z 2 



