t 2 49 3 



1 once imagined that, by mere ftagnatioh, ai? 

 "might become unfit for refpiration, or at leaft for 

 the burning of candles; but if this be the cafe, 

 and the change be produced gradually, it muft 

 require a long time for the purpofe. For on the 

 22d of September 1772, I examined a quantity of 

 common air, which had ; been kept in a phial, 

 without agitation, from May 1771, and found i£ 

 to be in no refpect worfe than frefh air, even by 

 the tefl of the nitrous air. 



The cryflallization of nitre makes no fenfible 

 alteration in the air in which the procefs is made. 

 For this purpofe I diffolved as much nitre as a 

 quantity of hot water would contain, and let it 

 cool under a receiver, {landing in water. 



November 6, 1772, a quantity of inflammable 

 air, which, by long keeping, had come to ex- 

 tinguifh flame, I obferved to fmell very much like 

 common air in which a mixture of iron filings 

 and brimftone had flood. It was riot* however, 

 quite fo ftrong, but it was equally noxious. 



Bifmuth and nickel are diffolved in the marine 

 acid with the application of a confide'rable degree 

 of heat; but little or no air is got from either of 

 them; but, what I thought a little remarkable, 

 both of them fmelled very much like Harrowgate 

 water. This fmell I have met with feveral times 

 in the courfe of my experiments, and in procefies 

 very different from one another. 



As I generally made ufe of mice in the ex- 

 periments which relate to refpiration, and fome 

 perfons may chufe to repeat them after me, and 

 purfue them farther than I have done ; it may be 



Vol. LXIL Kk . of 



