233 



On repeating the same experiments with diethylene-diamine, per- 

 fectly analogous phenomena were observed, but the reaction yielded 

 only one volatile base, which was immediately converted into a fixed 

 base. Analysed in a similar manner, and represented as salts, these 

 bases exhibit the following composition : 



Salt of diethylene-diammonium [(C 4 HJ" 2 H 4 N a ]" I a . 



Salt of diethylated diethylene-diammonium [(C 4 H 4 )" 2 (C 4 H 5 ) 2 H 2 N 2 ]" I 2 . 

 Salt of tetrethylated diethylene-diammonium [(C 4 H 4 )" 2 (C 4 H 5 ) 4 N 2 ]" I 2 . 



The same result is accomplished, but in a shorter and more elegant 

 manner, by substituting iodide of methyl for its ethylated homologue. 

 Already, at an earlier period, I have shown that iodide of methyl has 

 a remarkable tendency to yield the last product of substitution. 

 Thus, on treating iodide of methyl with ammonia, the iodide of 

 tetramethylammonium is alone obtained, together with a very large 

 proportion of iodide of ammonium. The action of iodide of methyl 

 with the ethylenated bases is perfectly analogous. The last product 

 of substitution is formed at once in notable quantity, and may be 

 purified by a simple crystallization. I have obtained in this manner, 

 without being embarrassed by the intermediate compounds, the iodide 

 of hexmethylated ethylene-diammonium and of tetramethylated 

 diethylene-diammonium . 



These results require no further explanation. 



In the present state of science we rely upon a certain number of 

 considerations which guide us in the construction of a chemical 

 formula. These are, the study of the origin of a body ; analysis ; 

 observation of the physical properties, and especially of the boiling- 

 point ; the determination of the vapour-density ; and lastly, the exa- 

 mination of its metamorphoses. I have endeavoured to look at the 

 question under discussion from these several points of view ; experi- 

 ment has given invariably the same reply. 



It follows from this controversy that the diatomic alcohols imitate 

 the monatomic alcohols in their deportment with ammonia. Ethyl 

 alcohol produces, as is well known, three ethylated ammonias, the 

 molecules of which occupy 4 volumes of vapour. 



Ethylamine H I N=4 volumes. 



