230 



In repeating the experiment of this able chemist, I have arrived, 

 as might have been expected, at exactly the same number. But this 

 number refers to the hydrated base, and it is easily seen that the 

 hydrated molecule, when in the state of vapour, must occupy 8 

 volumes. In calculating the theoretical density corresponding to 

 the diatomic formula when referred to 8 volumes, we arrive at the 

 number 1*35, which coincides in fact with the number obtained by 

 experiment. 



It is obvious that under the influence of heat the hydrated base 

 splits into anhydrous base (4 volumes) and water (4 volumes), 



and that, instead of taking the vapour-density of the intact hydrated 

 molecule, M. Cloez has determined the density of a mixture of an- 

 hydrous base and water, which on cooling combined again, repro- 

 ducing the hydrated compound. And here I must recall the observa- 

 tions of several chemists, especially those of M. Bineau, of M. 

 Kekule, and of M. H. Saint-Claire Deville, each of whom has had 

 the opportunity of explaining the anomalous vapour-densities in the 

 transitory decomposition of the compounds submitted to experiment ; 

 and I would quote particularly a note by Professor Kopp*, in which 

 this distinguished physicist has treated the question of anomalous 

 vapour- densities in a general manner. 



In the case before us, there is a very simple experiment, calculated 

 to remove all hypothesis from the above explanation, the determina- 

 tion of the vapour-density of the anhydrous base. 



The experiment made with a substance the purity of which had 

 previously been proved by analysis, led to the number 2*00, which 

 indeed absolutely coincides with the theoretical density of the 

 diatomic formula C 4 H 8 N a referred to 4 volumes. This theoretical 

 density is 2'07, whilst the formula of M. Cloez, likewise referred to 

 4 volumes, requires the theoretical density of TOO. 



The molecule of ethylene-diamine (formenamine) then, like those 

 of all other well-examined organic compounds, corresponds to 4- 

 volumes of vapour ; and the vapour-density of the base, far from 

 militating against the molecular value which I assign to this body, 

 furnishes on the contrary an additional and incontestable argument 

 in its favour. 



* Ann. de Chem. et de Pharm. cv. 390. 



