Dr. Hofmann on Aniline, Azobenzole, and Benzidine. 453 



and has been extensively tried with the most perfect success in the 

 laboratory of the Royal College of Chemistry. The facility of the 

 process, its rapidity, and the large amount of product it yields in 

 most cases, cannot fail materially to assist the study of the volatile 

 organic bases. 



During these experiments several observations were made, which 

 I beg leave to bring under the notice of the Society. 



When employing about double the amount of iron which is recom- 

 mended by M. Bechamp (2'5 instead of 1-2 of iron to 1 part of 

 nitrobenzole), Mr. Alfred Noble found that the latter portion of the 

 distillate solidified partly in the receiver and partly in the condenser. 

 Washed with hydrochloric acid from adhering aniline, and once or 

 twice recrystallized from boiling alcohol, the solid matter was ob- 

 tained in fine crystals of a yellowish-red colour, and fusing below 

 the boiling-point of water. These crystals possessed all the proper- 

 ties of azobenzole, which was moreover identified by combustion. 



0-260 gramme of substance gave 0*755 grm. of carbonic acid 

 and 0"134 grm. of water. 



The well-established formula of azobenzole, C,2 H^ N, requires the 

 following values : — 



Theory. 

 , A 



Equivalents. Per-centage. Experiment. 



Carbon 12 79-12 79-12 



Hydrogen .... 5 5*49 5-76 



Nitrogen 1 15-39 



10000 



The azobenzole obtained in this manner is so readily purified that 

 this process is greatly preferable to the action of alcoholic potassa 

 upon nitrobenzole, since the latter process simultaneously produces 

 several substances which can be separated only with difficulty from 

 the azobenzole. 



A portion of the azobenzole obtained in the above process was 

 converted by means of sulphuretted hydrogen into benzidine. Of 

 the beautifully crystallized compound, a platinum salt was made 

 which was analysed by Mr. Noble. 



0-268 grm. of the salt left 0-088 grm. =32-88 per cent, of 

 platinum. The formula Cij H,; N, HCl ; Pt Cl,^ requires 33-09 per 

 cent, of platinum. 



Benzidine exhibits a very interesting deportment with nitrous 

 acid; gently warmed in the gas of this acid, obtained by treatment 

 of starch with nitric acid, it gives rise to a powerful reaction. The 

 substance assumes an orange-red colour, and exhibits, after treatment 

 with water, when recrystallized from alcohol, all the properties of 

 azobenzole. 



The reproduction of this body from benzidine was moreover fixed 

 in the following numbers : — 



0-'J15 grm. of substance gave 0'623 grm. of carbonic acid, and 

 0-112 grm. of water. 



