ATMOSPHERICAL AIR. 5 



only to become blue, and were not melted, they gained 

 very little, if any, weight, and diminilhed the air only in 

 about the lame proportion with the black bones. 



Having by means of a burning lens heated 200 grains 

 of the poliilied needles in 24 ounce meafures of air (in 

 confequence of which they became of a dark colour) they 

 neither gained nor loft any weight, and the air was re- 

 duced to 19.5 ounce meafures, almoft completely phlo- 

 gifticated. 1 heated the lame quantity of thefe needles in 

 1 6.75 ounce meafures of air, when it was reduced to 

 13.5 ounce meafures, completely phlogifticated without 

 any mixture of fixed or inflammable air in it ; fo that the 

 diminution was in the proportion of 19.4 parts in one 

 hundncd. In another experiment 24.75 ounce meafures 

 of air were reduced to 20.25 ounce meafures nearly 

 phlogiilicated. It is evident, therefore, from thefe ex- 

 periments, that more phlogifticated air is found after 

 this procefs, than after that with the iron filings and 

 fulji'jur. 



BecjHirc by heating the needles over a quantity of water 

 the) Plight attradl moifture, which cannot be expelled 

 troll them withouL fome difficulty, I heated 200 grains 

 01 the fame needles in the open air, till they had aflumed 

 exactly the fame appearance with thofe that had diminifh- 

 ed the air in the preceding experiments, and found that 

 they had neither gained nor loft any fenfible weight. 

 The fame was the refult of whitening a quantity of black 

 bones in the open air. But to make this experiment with 

 accuracy, the bones fhould be calcined with the greateft 

 degree of heat, and made white with the leaft. 



In one experiment with A'^ery thin pieces of malleable 

 iron (viz. iron turnings) 38.5 ounce meafures of air 

 were reduced to 31,5 meafures, wholly phlogifticated, 

 which is in the proportion of the lofs of 19.5 parts in 

 100. I could not perceive that the iron had gained or 



loft 



