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parting the air feveral times through cold water, 

 the original quantity was diminished about y. In 

 the remainder a candle would not burn, and a 

 moufe would have died prefently. The fmeil of 

 this air was exceedingly pungent, but different from 

 that of the putrid effluvium. A moufe lived per- 

 fectly well in this air, thus affected with the ace- 

 tous fermentation ; after it had flood feveral days 

 mixed with four times the quantity of fixed air. 



All the kinds. of factitious air on which I have 

 yet made the experiment are highly noxious to 

 animals, except that which is extracted from fait- 

 petre, or alum ; but in this even acandle burned jufl 

 as in common air. In one quantity which I got from 

 fait-petre a candle not only burned, but the flame 

 was increafed, and fomething was heard like a 

 biffing, fimilar to the decrepitation of nitre in an 

 open fire. This experiment was made when the 

 air was frefh made, and while it probably con- 

 tained fome particles of nitre, which would have 

 been depofited afterwards. The air was extracted 

 from thefe fubftances by putting them into a gun 

 barrel, which was much corroded and foon fpoiled by 

 the experiment. What effect this circumftance 

 may have had upon the air I have not confidered. 



November 6, 1772, I had the curioiity to exa- 

 mine the ftate of a quantity of this air, which had 

 been extracted from fait- petre above a year, and 

 which at firft was perfectly wholefome ; when, to. 

 my very great furprize, I found that it was be- 

 come, in the higher! degree, noxious. It made 

 no effervescence with nitrous air, and a moufe died, 

 the moment it was put into it. I had not, how- 

 ever, warned it in rain, water quite ten minutes 



(and. 



