V.] JOSEPH PRIESTLEY. Ill 



that the new air behaved with "nitrous gas" in the 

 same way as the dephlogisticated part of common air 

 does ; l but that, instead of being diminished to four- 

 fifths, it almost completely vanished, and, therefore, 

 showed itself to be "between five and six times as 

 good as the best common air I have ever met with." 2 

 As this new air thus appeared to be completely free 

 from phlogiston, Priestley called it " dephlogisticated 



air/' 



What was the nature of this air ? Priestley found 

 that the same kind of air was to be obtained by 

 moistening with the spirit of nitre (which he terms 

 nitrous acid) any kind of earth that is free from 

 phlogiston, and applying heat ; and consequently he 

 says : " There remained no doubt on my mind but 

 that the atmospherical air, or the thing that we 

 breathe, consists of the nitrous acid and earth, with 

 so much phlogiston as is necessary to its elasticity, 

 and likewise so much more as is required to bring it 

 from its state of perfect purity to the mean condition 

 in which we find it." 3 



Priestley's view, in fact, is that atmospheric air is 

 a kind of saltpetre, in which the potash is replaced 

 by some unknown earth. And in speculating on the 

 manner in which saltpetre is formed, he enunciates 

 the hypothesis, " that nitre is formed by a real 

 decomposition of the air itself, the bases that are 

 presented to it having, in such circumstances, a nearer 



1 " Experiments and Observations on Different Kinds of Air," voL 

 ii. p. 40. 2 Ibid. p. 48. 3 Ibid. p. 55. 



