OF THE ATMOSPHERIC ELEMENTS. 325 



The atmosphere, and these chemically active com- 

 pounds, contain the same elements,, but their mode of 

 combining is different; and what is, in the one case,, 

 poisonous to the highest degree, is, in the other, ren- 

 dered salubrious, and essential to all organized beings. 



Nitrogen gas may be regarded in the light of a diluent 

 to the oxygen. In its pure state it is only characterised 

 by its negative properties. It will not burn, or act as 

 a supporter of combustion. Animals speedily perish if 

 confined in it ; but they die rather through the absence 

 of oxygen than from any poisonous property of this gas. 

 Yet, in combination, we find nitrogen exhibiting powers 

 of a most energetic character. In addition to the ful- 

 minating compounds and the explosive substances 

 already named, which are among the most remarkable 

 instances of unstable affinity with which we are ac- 

 quainted, we have also the well-known pungent body, 

 ammonia. From the analogous nature of this volatile 

 compound, and the fixed alkalies soda and potash, it 

 was inferred that it must, like them, be an oxide of a 

 metallic base. Davy exposed ammonia to the action of 

 potassium, and to the influence of the voltaic arc pro- 

 duced from 2,000 double plates, without at all changing 

 its character. From its slight tendency to combination, 

 and from its being found abundantly in the rgans of 

 animals feeding on substances that do not contain it, it 

 is, however, probably a compound body. A phenomenon 

 of an obscure and mysterious character is presented, 

 the formation of the <( amrnoniacal amalgam," as it 

 called. 



Mercury, being mixed with an ammoniacal salt, is 

 exposed to powerful galvanic action ; and a compound, 

 maintaining its metallic appearance, but of considerable 

 lightness and very porous, presents itself.* This prepa- 



* Electro-chemical Researches on the Decompositions of the Earths, 

 with observations on the Metals obtained from the Alkaline Earths, 

 and on the Amalgam procured from Ammonia : by Sir Humphry 

 Davy; Philosophical Transactions, 1808, and collected works, 

 vol. v. p. 10-,>. 



