46 Chemistjy. [Lecture 25. 



of common air nearly as 94-2-6 to 1000. Com- 

 pared with hydrogen its specific gravity is as 13 

 tol. 



It is immediately destructive of life if breathed 

 without a mixture of oxygen gas; though it 

 may be doubted whether the animal does not 

 rather die from the want of oxygen gas than 

 from any noxious quality in the nitrogen ; since, 

 when mixed with the former, every moment's 

 experience convinces us that nitrogen gas is not 

 only harmless, but even salutary. Its use in the 

 atmosphere appears indeed to be to dilute the 

 oxygen, and prevent its too violent effects on 

 the animal frame. 



Nitrogen unites with oxygen, besides its com- 

 bination forming atmospheric air, in four dif- 

 ferent proportions, constituting nitrous oxide, 

 nitric oxide, nitrous acid, and nitric acid. 



Nitrogen gas extinguishes flame for the same 

 reason that it extinguishes life, namely, from 

 wanting that principle which supports both 

 oxygen. From this circumstance we may see 

 the absurdity of the common practice when a 

 room or a house is set on fire, which is, to open 

 all the doors and windows, by which a constant 

 supply of fresh air is produced, so as to enable 

 the fire to burn with greater violence. 



In the gaseous form there are two combina- 

 tions of nitrogen with oxygen, which it is pro- 

 per to notice from their singular properties. 

 The one is that to which one of the first chemists 



