6 



Dr. Hofmann on Aniline-yellow. 



[Nov. 19, 



I have ascertained that toluidine furnishes, both with kinone and chlo- 

 ranile, analogous compounds. The higher percentage of carbon observed 

 by M. Hesse may possibly find a satisfactory explanation in the con- 

 tamination with toluidine of the aniline which has served for his experi- 

 ments. Commercial aniline invariably contains more or less toluidine. 



V. " Eesearches on Colouring Matters derived from Coal-tar. — 

 I. On Aniline-yellow." By A. W. Hofmann, LL.D., F.R.S. 

 Eeceived June 29, 1863. 



In a short paper submitted to the Royal Society in the commencement 

 of last year, 1 have described a few experiments on the remarkable new 

 colouring matters derived from aniline, which of late have attracted such 

 general attention. This paper had more particularly reference to aniline- 

 crimson, the industrial production of which, in the hands of Mr. E. 

 Nicholson, has reached so high a degree of perfection that the analysis 

 of this compound and of its numerous salts presented no serious diffi- 

 culty. But the problem was not solved by establishing the formula of 

 rosaniline and its salts : by far the more important obstacles remained to 

 be conquered ; the molecular constitution of rosaniline, on which at that 

 time I had not even been able to offer an hypothesis, and the genesis of 

 this well-defined triamine from aniline, had still to be traced. Since that 

 time considerable progress has been made towards the solution of this 

 problem. Some of the latest observations which I have had the honour 

 of submitting to the Boyal Society will doubtless help to untie this knot. 

 Nevertheless many doubtful points still remain to be cleared up, and I 

 .found it desirable for the better elucidation of the subject to investigate 

 simultaneously several of the other artificial organic colouring matters, in 

 order to trace if possible analogies of composition and constitution in 

 these substances, which, it was reasonable to hope, would throw some light 

 upon the principal subject of the inquiry. 



The present moment appeared to be particularly appropriate for an 

 investigation of this kind. The International Exhibition has brought 

 together a collection of these new bodies, such as no other occasion 

 could possibly have assembled in one place and at one time, display- 

 ing in a remarkable manner the rapidity with which the industry 

 of our time assimilates and, in many cases, anticipates the results of pure 

 science. 



I have commenced the study of a few of the new colouring matters 

 which several of the distinguished exhibitors of these compounds have 

 placed at my disposal — a study which has been greatly facilitated by the 

 zeal and experimental skill of a young chemist. Dr. A. Geyger, who has 

 assisted me in these experiments. Owing to the number of these sub- 

 stances, and in some cases the difficulties of the reactions to be disen- 

 tangled, some time must elapse before their investigation can be finished. 



