Mr. Cavennisn’s Experiments on A,r. 15g 
mercury will be revived; but, if the foilution of fublimate cor- 
rofive be precipitated by lime-water, it feems no air will be pro- 
duced. Here then we fee, rft, that the calx of mercury unites 
with fixed air; and, 2dly, that this fixed air is, during the 
revivification of the mercury, converted into dephlogitticated 
air. Again; let one ounce of red precipitate, which, according 
to Mr. CAVENDISH, contains no nitrous acid, be diftilled with 
two ounces of filings of iron; this quantity of precipitate, 
which, if diftilled by itfelf, would yield 60 ounce meafures of 
dephlogifticated air, will, when diftilled with this proportion 
of filings of iron, yield 40 ounce meafures of fixed air, as Dr. 
Prrestiey has fhewn in his laft paper: whichever way this 
_is explained, fome or other of my opinions are confirmed; for 
either the mercurial calx is already combined with fixed air 
(which I believe to be the cafe), and this air paffes undecom- 
pofed, becaufe the mercury extracts phlogiften from the iron 3 
or it contains dephlogifticated air, which is converted into fixed 
_ air by its union with the phlogifton of the iron. 
If precipitate per fe be digefted in marine acid, the mercury 
will be revived (3 Bere. 415.). Now this calx does not de- 
» phlogifticate the marine acid; for this acid, when dephlogitti- 
cated, diflolves mercury; how then does it revive it, if not by 
expelling the fixed air contained in it, which in the moment of 
its expulfion is decompofed, leaving its pilogEron to the mercu- 
zy, which is thereby revived? 
Again: if litharge be heated in a gun-barrel, it will afford more 
fixed and lefs dephlogifticated air than if heated in glafs or 
earthen veffels. Does not this happen, becaufe the calx of 
lead, receiving fome phlogifton from the metal, does not de- 
_ phiogifticate fo great a proportion of the fixed air as it other- 
wife would? 
Fur- — 
