[ i6x ] 



any alteration would be made in the conftitution of 

 fixed air, by this mixture of iron filings and brim- 

 ftone. I therefore put a mixture of this kind into a 

 quantity of as pure fixed air as I could make, and 

 confined the whole in quickfilver, left the water 

 mould abforbe it before the effects of the mixture 

 could take place. The confequence was, that the 

 fixed air was diminished, and the quickfilver rofe in the 

 vefTel, till about the fifth part was occupied by it j and, 

 as near as I could judge, the procefs went on, in all 

 refpeds, as if the air in the infide had been common 

 air. 



What is moft remarkable, in the refult of this ex- 

 periment, is, that the fixed air, into which this mix- 

 ture had been put, and which had been in part di- 

 minished by it, was in part alfo rendered infoluble 

 in water by this means. I made this experiment 

 four times, with the greateft care, and obferved, 

 that in two of them about one fixth, and in the 

 other two about one fourteenth, of the original 

 quantity, was fuch as could not be abforbed by wa- 

 ter, but continued permanently elaftic. Left I mould 

 have made any miftake with refpect to the purity of 

 the fixed air, the laft time that I made the experi- 

 ment, I fet part of the fixed air, which I made ufe 

 of, in a feparate vefTel, and found it to be exceed- 

 ingly pure, fo as to be almoft wholly abforbed by 

 water ; whereas the other part, to which I had put 

 the mixture, was far from being fo. 



In one of thefe cafes, in which fixed air was made 

 immifcible with water, it appeared to be not very 

 noxious to animals 5 but in another cafe, a rnoufe 

 died in it pretty foon. 



Vol. LXII. Y As 



