CHAPTER X 



NITRE, NITRIC ACID, AND NITROGEN 



A. NITROGEN 



Speculations as to the nature of nitrous air and of 

 azote. In the preceding chapters the nature and properties 

 of some of the common gases have been described. Thus 

 Black's " fixed air" has been shown to be a product of combus- 

 tion, a compound substance containing carbon and oxygen. 

 Cavendish's "inflammable air," on the other hand, is a 

 simple substance, which unites with oxygen to form water. 

 The nature of Priestley's "nitrous air" still remains, 

 however, to be discussed. 



The fact that nitrous air combines with oxygen to form 

 brown nitrous fumes, and with oxygen and water to form nitric 

 acid suggested that the gas might be the "elementary 

 principle " from which nitric acid was derived, just as 

 carbonic, sulphuric, and phosphoric acids were derived from 

 carbon, sulphur, and phosphorus respectively. On the other 

 hand, the fact that nitrous air could be " diminished " by iron 

 filings and sulphur certainly suggested that it contained 

 oxygen; the product, it is true, did not behave like a 

 deoxidised nitrous air, since it supported combustion almost 

 as well as oxygen itself; but it undoubtedly contained 

 oxygen, which could scarcely be derived from any source 

 but the nitrous air. 



