rji4 ' Dr, Priestley’s Experiments 
This is not quite fo much in proportion as in the preceding 
experiment, but abundantly more than the weight of the 
plumbago. 
In 8 oz. m. of inflammable air I revived minium (which I 
found to have exadlly the fame effedt in this procefs as red pre- 
cipitate, or precipitate per fe ), till it was reduced to 1.2 oz. 
; m. ; and of this 0.028 oz. m. was fixed air, which would ex- 
ceed the weight of the plumbago more than three times. In 
reviving lead from maflicot (which I prepared by expelling the 
pure air from minium) I had no fixed air in the refiduum. 
In 7 oz. m. of inflammable air from tin by fpirit of fait, 
I revived red precipitate till it was reduced to 1.1 oz. m. ; and 
In this the fixed air was fomething more than in proportion to 
that in the laft experiment. 
In my laft volume of Experiments, p. 30. I mentioned fome 
inftances of the revival of red precipitate in inflammable air, 
without finding any fixed air, though in one 1 perceived a 
flight appearance of it. To this I can only fay, that I now 
always find it, and have, in the preceding cafes, meafured the 
quantity of it ; fo that, though I did not find any before, I 
muft prefume that I did not ufe the fame precautions that I 
did at this time : and it is poffible, that I might not attend to 
the effe£t of admitting a large quantity of water to a fmall 
quantity of fixed air, which would prefently abforb the 
greateft part of it. I alfo think I recollect, that I then con- 
tinued the procefs as far as I poffibly could, and confequently 
left very little air in the vefiel ; whereas I now purpofely left 
a good deal, that the admifilon of water might have lefs 
effe£t on the fixed air diffufed through it. 
This alio may be faid in favour of the greater accuracy of 
*my prefent experiments* that they intlrely remove a very great 
difficulty* 
