General Principles. 45 



this mixture of the gasses, they will be condensed, 

 and form pure nitric acid. 



Nitrogen has not been made apparent to our 

 senses otherwise than in a state of combination. 

 The simplest form is that of a gas, or combined 

 with caloric. In this state it forms about 77 

 parts in the 100 of our atmosphere, and is that 

 part of the common air which will neither sup- 

 port flame nor animal life. On this last account 

 it was formerly known by the name of azote * 

 or azotic gas, because it was destructive of ani- 

 mal life. As it constitutes a part of the atmo- 

 spheric air, and is incombustible, it is easily 

 procured by abstracting that part of the air 

 which is destroyed by combustion, viz. the oxy- 

 gen gas. Thus, if a portion of iron filings and 

 sulphur, moistened with water, is put into a 

 vessel with common air, the oxygen will be ab- 

 sorbed, and will go to oxidize the metal and the 

 sulphur, and the nitrogen gas will remain. The 

 same effect will be produced by phosphorus 

 alone, inclosed in a similar vessel with common 

 air. The phosphorus will undergo a slow com- 

 bustion, will be oxidized, or converted into 

 phosphoric acid, and the nitrogen gas will re- 

 main behind. 



Nitrogen gas is considerably lighter than 

 common air, and consequently much lighter 

 than oxygen gas. Its specific gravity is to that 



* From the Greek privative (aor al, Latin), and zoe, 

 life. 



