Dr. Hofmann on the Diatomic Ammonias. 



73 



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

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

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

 a remarkable tendency to yield the last product of substitution. 

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

 tetramethylammonium is alone obtained, together with a very large 

 proportion of iodide of ammonium. The action of iodide of methyle 

 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 hexm ethylated 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. 



ojfc.i 



Ethylamine H VN =4 volumes. 

 H 



c 4 h; 



Diethylamine C 4 H 

 H 

 C 4 H 



Triethylamine C 4 H 



cX 



-N=4 volumes. 



►N = 4 volumes. 



Ethylene-diamine 



In a similar manner we find that glycol, the diatomic alcohol of 

 ethylene, the discovery of which we owe to the remarkable labours of 

 M. Wurtz, gives rise to three diatomic bases, corresponding to 2 

 molecules of ammonia, and representing likewise 4 volumes of vapour. 



(C t H 4 )»- 



H 2 



H 2 



(<W 



Diethylene-diamine (C 4 H 4 )" 



H 2 



(c h y r 



Triethylene-diamine (€* H 4 )" 

 (C 4 HJ"_ 

 The two first terms of this series are the bases which M. Cloez 



-N 2 =4 volumes. 



•N 2 =4 volumes. 



»N Q =4 volumes. 



