72 Royal Society : — 



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 ethyle. After two hours' digestion at 

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

 evaporation yields a crystalline iodide, 



C 1C H 22 N 2 I 2 =C 12 H J2 (C 2 H 5 ) 2 N 2 1 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 16 H 20 N 2 =C )2 H 10 (C 2 H 5 ) 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 I0 H 22 N 2 Cl 2 2PtCl 2 . 



* When diethylbenzidine is treated again with iodide of ethyle, 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- 

 benzidine ^ ^ ^_ ^ -^ ^ ff ^ 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 so H 80 N a Cl 2 ,2PtCl 2 . 



The further action of iodide of ethyle 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 methyle, on the other hand, acts with greate nergy. An 

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

 pound. 



The iodide 



C 22 H 34 N 2 I a =C u H 8 (C 2 II 3 ) 4 (CH 3 ) 2 N a I a 



is very difficultly soluble in absolute alcohol, but dissolves with 

 facility in boiling water, from which it is deposited on coolin™-, in 

 long beautiful needles. The solution of this iodide is no longer pre- 

 cipitated by ammonia, but yields with oxide of silver a powerfully 

 alkaline solution, exhibiting all the characters of the completely sub- 

 stituted ammonium- and diammonium-bases discovered bv Professor 

 Hofmann. The solution of this dimethyl-tetrethylated base, which 

 contains 



vs 22 n 36 iv 2 kj.,— g > U 2 , 



