521 



the bases and their salts being easily obtained in crystals, which are 

 often capable of measurement. 



It was under peculiar circumstances that my attention was drawn 

 again to the study of the aromatic diamines. I am indebted to 

 Dr. Alphons Oppenheim for the communication of a specimen of a 

 crystallized base, which had been obtained as a secondary product in 

 the Aniline Works of M. Ch. Collin of Paris. The first combustions 

 proved to me that this substance was one of the diatomic compounds 

 which I had repeatedly endeavoured to produce. The crystals were 

 found to contain 



C 7 H 10 N 2 



V IN,, 



H 2 j 



which is the formula of toluylene-diamine, the primary diamine of 

 the toluyl-series. The intimate relation of this compound with the 

 ethylene-bases, which I have lately studied, induced me to pursue the 

 subject further. M. Ch. Collin has had the kindness to furnish me 

 with a most liberal supply of this interesting substance, accompanied 

 by a very lucid and elaborate statement of the circumstances under 

 which it is produced, drawn up by Dr. Coblentz, the chemical director 

 of the factory. I have thus been enabled to verify the formula above 

 given by the analysis of several salts. 



There could be no doubt about the reaction which, in the manu- 

 facturing processes of M. Collin, had given rise to the formation of this 

 substance. It obviously owed its origin to dinitrotoluol accidentally 

 produced from the toluol invariably present in commercial benzol. 

 Experiments have not failed to verify this view. Dinitrotoluol, pre- 

 pared by the usual process from toluol, when distilled with a mixture 

 of iron and acetic acid the method of reduction now generally 

 adopted in the manufacture of aniline has furnished the crystalline 

 alkaloid of M. Collin with all its properties. The identity was proved 

 moreover by analysis. 



The rest is rapidly told. The examination was at once extended 

 to the dinitro- compounds of the homologues of toluol, and more 

 especially to dinitrobenzol. The behaviour of these substances under 

 the influence of acetate of iron, as might have been expected, is per- 

 fectly analogous to that of dinitrotoluol. It is my intention to lay 

 before the Society a detailed account of the diatomic bases which 



