Mr. er § Remarks. ge 
air, fe Gos 24.00 me a mixture of dephlogifticated and inflam-. 
mable air, but. chiefly the latter. The fame quantity of iron. 
filings, taken from the fame parcel, was-then diffolved in di- 
luted oil of vitriol, fo as to leave only the plumbago and other: 
impurities. Thefe mixed with 500 grains of the fame red 
precipitate, and treated as before, yielded gz200 grain mea- 
fures of fixed air, and:4200 of dephlogifticated air, of an in-. 
different quality, but without any fenfible mixture of-inflam--- 
mable air. It appears, therefore, that lefs fixed air was pro- 
duced when the red precipitate was mixed with the iron filings. 
in fubftance, than when mixed only with the plumbago’ and: 
other impurities; which fhews, that its production was not: 
owing to the iron itfelf, which feems to. contain. no fixed air, , 
but to.the plumbago, which contains a great deal. The rea-- 
fon, in all probability, why lefs fixed air was produced in the. 
firftt cafe than the latter is, that in the former more of the- 
plumbago efcaped: being decompounded by the red precipitate . 
than in the other. It muft be obferved, however, that the 
filings ufed in this. experiment were mixed: with about ,’,th of. 
their weight of -brafs, which. was not difcovered till they were: 
diffolved:in the acid, and which makes the experiment lefs de-- 
cifive. than it would otherwife be. ‘The quantity of fixed’air- 
obtained is alfo much greater than, according to Mr. Brere-- 
MAN’s.experiment,. could. be yielded by the plumbago ufually - 
contained in 1000 grains of iron; fo that though the experi- 
ment feems to fhew that the fixed air was only produced by~ 
the decompofition of the impurities in the filings, yet it. cer-- 
tainly ought to be repeated in a-more accurate manner. 
Before I conclude this paper, it may be proper to {um up> 
the {tate of the argument on this fubje€&t. There are five me-- 
thods of phlogiftication confidered by me in my paper on air3- 
namely, 
