587 



Benzidine, when expressed by the formula 



C 12 H 12 N 2 , 



presents itself as a well-defined diacid diamine. The molecular con- 

 struction of the diatomic base remained to be decided. 



I have endeavoured to solve this problem by the process of 

 ethylation, as yet the simplest and the best guide in determining 

 questions of this kind. Benzidine in the presence of alcohol is 

 rapidly attacked by iodide of ethyl. After two hours' digestion at 

 100 C. in sealed tubes, the reaction is complete. The solution on 

 evaporation yields a crystalline iodide, 



C 16 H 22 N 2 I 2 =C 12 H, 2 (C 2 H 8 ) 2 N 2 I 2 , 



from which ammonia separates a solid crystalline base very similar 

 to benzidine. This compound, which fuses at 65 C., and resolidi- 

 fies at 60 C., is diethylbenzidine : 



C ie H 20 N 2 =C, 3 H 10 (C a H s ) 2 N 2> 



which forms well-crystallizable salts with the acids, and yields with 

 dichloride of platinum a difficultly soluble crystalline platinum- salt 

 containing C 16 H 22 N 2 C1 2 2PtCl 2 . 



When diethylbenzidine is treated again with iodide of ethyl, the 

 phenomena previously observed repeat themselves. The iodide 



C 20 H 30 N 2 I 2 =C 12 H 10 (C 2 H 5 ) 4 N 2 I 2 



is formed, which when decomposed by ammonia yields tetrethyl- 

 lenMine C 20 H 28 N 2 =C 12 H 8 (C 2 H 5 ) 4 N, 



Tetrethylbenzidine resembles the diethylated and the non-ethylated 

 base. It fuses at 85 C., resolidifying at 80 C., produces with the 

 acids crystalline compounds, and furnishes with dichloride of plati- 

 num a platinum-salt of the formula 



C 20 H 30 N 2 Cl 2 ,2PtCl 2 . 



The further action of iodide of ethyl upon tetrethylbenzidine is 

 extremely slow. After 12 hours' digestion at 100 C. only a very 

 minute quantity of the base had been transformed into an iodide. 

 Iodide of methyl, on the other hand, acts with great energy. An 

 hour's digestion is sufficient to produce the final diammonium-com- 

 pound. 



The iodide 



C 22 H 34 N 2 1 2 =C 12 H 8 (C 2 H 5 ) 4 (CH 3 ) 2 N 2 1 2 



is very difficultly soluble in absolute alcohol, but dissolves with 

 facility in boiling water, from which it is deposited on cooling, in 



