406 COMPOUNDS OF HYDROGEN. 



upon the respiratory organs, as to make the inspiration of it, 

 even in a highly diluted state, a most painful and even dange- 

 rous experiment (Traite, I. 340). 



SECTION III. 



HYDROGEN AND NITROGEN. 

 AMIDOGEN. 



Eg. 202 or 16.9 ; N H 2 or Ad; not isolable. 



Hydrogen and nitrogen do not combine directly, but three 

 compounds of these elements are generally admitted to exist, 

 only one of which, however, ammonia, can be obtained in a 

 separate state. It is even highly probable that amidogen is the 

 only direct combination of these elements, and that the other 

 two are compounds of amidogen with hydrogen. These com- 

 pounds are 



Amidogen . . N H 2 NH 2 



Ammonia . . NH 2 + H . . . N H 3 

 Ammonium. . NH 2 + 2H. . . NH 4 



Judging from the nature of the combinations in which ami- 

 dogen is found, it appears to be a compound of the salt-radical 

 class, in which it occupies a low place, superior to oxygen, but 

 considerably inferior to chlorine, or perhaps even sulphur. The 

 white precipitate of pharmacy, formed on adding ammonia to a 

 solution of chloride of mercury, is a body in which amidogen was 

 proved to exist by the analysis of Dr. Kane, which has been re- 

 peated and confirmed by Ullgren. The term amide being applied 

 to combinations of amidogen, and the symbol Ad assigned to it, 

 white precipitate is a compound of chloride of mercury with 

 amide of mercury, and is expressed by HgCl + HgAd. Dr. 

 Kane has also shown that the black compound obtained on 

 washing calomel or subchloride of mercury with ammonia, is a 

 corresponding combination of subchloride with subamide of 

 mercury, Hg 2 Cl + Hg 2 Ad ; and he has ascertained the existence 

 of amidogen in a variety of other mercurial compounds. But 

 it is to be observed of the metallic combinations of amidogen, 

 that those which have been certainly established are confined to 

 that metal, and also that amides of mercury have never been 



