JOSEPH PRIESTLEY. g9 



air with a remarkably vigorous flame, very much like that enlarged flame with 

 which a candle burns in nitrous air, exposed to iron or lime of sulphur ; but, as I 

 had got nothing like this remarkable appearance from any kind of air besides 

 this particular modification of nitrous air, and I knew no nitrous acid was used 

 in the preparation of mereurius caleinatus, I was utterly at a loss how to account 

 for it. 



" In this case also, though I did not give sufficient attention to the circum- 

 stance at that time, the flame of the candle, besides being larger, burned with 

 more splendor and heat than in that species of nitrous air ; and a piece of red- 

 hot wood sparkled in it, exactly like paper dipped in a solution of nitre, and it 

 consumed very fast an experiment which I had never thought of trying with 

 nitrous air." l 



Priestley obtained the same sort of air from red lead, but, as he 

 says himself, he remained in ignorance of the properties of this new 

 kind of air for seven months, or until March, 1775, 2 when he found that 

 the new air behaved with " nitrous gas " in the same way as the 

 dephlogisticated part of common air does ; 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." 3 As this new air thus appeared 

 to be completely free from phlogiston, Priestley called it " dephlogis- 

 ticated 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 re- 

 mained 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." 4 



Priestley's view, in fact, is that atmospheric air is a kind of saltpe- 

 tre, 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 affinity with the spirit of nitre than that kind of earth with 

 which it is united in the atmosphere." 6 



It would have been hard for the most ingenious person to have 

 wandered farther from the truth than Priestley does in this hypothe- 

 sis of his and though Lavoisier undoubtedly treated Priestley very 

 ill, and pretended to have discovered dephlogisticated air, or oxygen, 

 as he called it, independently, we can almost forgive him when we re- 



1 " Experiments and Observations on Different Kinds of Air," vol. ii., pp. 34, 35. 



2 Ibid., p. 40. 3 Ibid., p. 48. 4 Ibid., p. 55. 

 5 Ibid., p. 60. The italics are Priestley's own. 



