Dr. Hofmann on the Diatomic Ammonias. 69 



have pointed out, does not admit the simple equation which I have 

 given for the formation of this body ; he denies that it is simply 

 formed by the union of the two compounds reacting upon each 

 other. According to his opinion it is produced in a secondary re- 

 action, occasioned by the intervention of heat. My experiments do 

 not confirm this opinion. A mixture of dibromide of ethylene and 

 alcoholic ammonia allowed to stand for some time at the ordinary 

 temperature, deposited a quantity of crystals, from which I was en- 

 abled to extract, without distillation, simply by successive crystal- 

 lizations, absolutely pure salt of ethylene-diamine, as proved by the 

 analysis of the bromide, the chloride, and the platinum-salt. 



In discussing the numbers which I have obtained in analysing the 

 hydrate and the hydroehlorate of the first base, M. Cloez quotes the 

 results on which he founds his own formula. A glance at these 

 figures will show unmistakeably that they agree much better with 

 my formula than with the one which he defends. The following 

 are the analytical details of our analyses, together with the theo- 

 retical values required by each formula : — 



Every experimentalist has incontestably the first right of inter- 

 preting his analytical results ; knowing, as he does, his methods, he 

 will do it generally much better than any other person. In the case 

 before us, however, I believe very few chemists would have inter- 

 preted the results of analysis as M. Cloez has done. As far as I 

 am concerned, I would always prefer to admit having lost 0-2 per 

 cent, of hydrogen, to calculating a formula requiring 2*25 per cent, 

 of hydrogen less than had been obtained by experiment. I would 

 prefer this especially in analysing a substance like ethylene-diamine, 

 attracting carbonic acid with the utmost avidity — a trace of which 

 would very appreciably lower the experimental hydrogen — and con- 

 taining so high a percentage of hydrogen, that the presence even 

 of a small quantity of water would produce a somewhat similar 

 effect. 



The results which M. Cloez has obtained in the analysis of the 

 hydroehlorate are not less in favour of my views. He finds 1*28 per 

 cent, of hydrogen more than required by his formula, whilst ad- 

 mitting my theory, he would not have lost more than 0*13 per 

 cent. 



I have since examined several other salts of ethylene-diamine, and 

 the results fully confirm the conclusions drawn from my former 

 analyses. It would be useless to quote these additional experiments, 

 but I will mention the characteristic numbers furnished by the ana- 

 lysis of the anhydrous base, since the diminution of the equivalent 

 exhibits in a more striking manner the differences between the 

 theoretical values of the two formulae. Ethylene- diamine retains the 

 water with the greatest energy, and it is in fact only by protracted 



