90 Anniversary Meeting. [Nov. 30, 



monamines of the alcohol radicals — that is, a system of bases in which one 

 third of the hydrogen of the ammonia was replaced by the hydrocarbon, 

 the existence of which (it may be noticed) had been predicted by Liebig 

 as a consequence of his views as to the composition of the organic bases. 

 The experiments of Hofmann were in the same direction as those of 

 Wurtz, but of far more general application. By the action of the iodides 

 of the alcohol radicals upon ammonia, Hofmann replaced successively the 

 three atoms of hydrogen which its molecule contains by these hydro- 

 carbons — a method fraught with important results, both theoretical and 

 practical, with which all chemists are familiar. 



Among other consequences, this method placed the theory of types on 

 a solid experimental foundation, which served as the basis of its future 

 development. A critical test was given, by which the constitution of 

 any given " ammonia " could be ascertained, the number of derivatives 

 of the " ammonia " when subjected to the action of iodide of ethyl cor- 

 responding to the number of atoms of hydrogen which it still retained 

 unreplaced by hydrocarbon. Hofmann applied this test to aniline, and 

 demonstrated, by the successive formation of ethyl-aniline and diethyl- 

 aniline, that this base belonged to the primary monamine class, containing 

 two atoms of hydrogen unreplaced by hydrocarbon. To trace out, how- 

 ever slightly, the consequences of this method would be a serious task 

 indeed. It is sufficient to say that the views at present held by 

 chemists as to the molecular constitution of water, according to which 

 water is regarded, like ammonia, as a typical molecule, but containing 

 two atoms of hydrogen (instead of, as in the other case, three) replace- 

 able by the alcohol radicals, are based upon experimental evidence for 

 which the very same instrument of research, the iodide of ethyl, and 

 methods in all respects analogous to those by which Hofmann thus 

 established the constitution of aniline were employed. 



According to these views triethylaniline represented ammonia in which 

 all possible substitutions of this order had been effected. However, Hof- 

 mann applied his test to this substance, and obtained a most remarkable 

 result. A molecule of iodide of ethyl combines with a molecule of this 

 substance, giving rise to the iodide of a molecular group, behaving like 

 potassium or sodium, " a true organic metal in all its bearings." The 

 ground of this assertion is, that this iodide of tetrethylammonium, when 

 treated with freshly precipitated oxide of silver, is decomposed with the 

 formation of an oxide of the " organic metal " possessing the main features 

 of potash. This train of investigation has not as yet been adequately 

 pursued ; but the fundamental importance of this experiment, in reference 

 to our knowledge of the elemental bodies, cannot be doubted. 



The first memoir on the Phosphorus bases, in which the existence of a 

 class of phosphorus bases analogous to the compound ammonias was 

 experimentally established, was published in conjunction with M. Cahours. 

 In three subsequent memoirs these compounds were further investigated 



