32 On the doctrine 



I have recited one cafe of phlogifticated air being 

 formed by expofmg rufted iron to inflammable air, which 

 muft have been formed by the oxygen in the ruft and 

 the phlogifton in the air. There is, however, much 

 uncertainty in this refult, depending on circumflances 

 which I have not been able to afcertain. But one clear 

 cafe of the kind is fufficient proof of the hypothefis, 

 and I have met with feveral. 



On the I <;th of Auguft 1799 I examined a quantity 

 of inflammable air which had been confined by mercury 

 with dry iron rufted in nitrous acid from the 1 8th of 

 ]Vlarch i 798, and found nothing inflammable in it, 

 though there was no apparent change in the colour of 

 the iron. This was alfo the cafe of another quantity of 

 the fame kind of air which had been confined in the fame 

 manner from the 14th of July. At the fame time, how- 

 ever, another quantity of inflammable air that had been 

 confined the fame time, and in the fame manner, with 

 iron rufted in vitriolic acid was not much changed, 

 thoueh the iron was become black. 



o 



Since pure nitrous air wholly vanifhes when it unites 

 w'ith pure dephlogifticated air, the phlogifticated air that 

 is found after heating iron in it muft have been formed 

 from fome oxygen contained in the nitrous air and phlo- 

 gifton from the iron. After heating turnings of caft iron 

 in 5^ ounce meafures of nitrous air from mercury it was 

 reduced to 3-^ ounce meafures, and by wafhing in water 

 to 2^, one ounce meafure having been fixed air. But 

 when I heated malleable iron in 60 ounce meafures of 

 the fame nitrous air it was reduced to 24 ounce meafures, 

 all phlogifticated. When I continued this procefs beyond 

 the point of greateft diminution, the air produced was 

 inflammable. 



Since water contains but a fmall quantity of air in pro- 

 portion to its bulk, and .generally confiderably purer than 



tftat 



