o 16 Dr. Priestley’s Experiments and Obfervations on 
thing with the fubftance from which it was procured, only 
volatilized, and united to water, it will follow, that any fub- 
ftance imbibing inflammable air muff become compounded with 
that other fubftance from which the inflammable air was pro- 
duced ; and therefore, all the inferences recited in the former 
Paper, which tend to eftablifh the doctrine of phlogifton, 
muft be admitted. 
It will be afked, what becomes of the dephlogifticated air 
which is certainly expelled from red precipitate when it is 
heated in inflammable air, and converted into running mer- 
cury, if the inflammable air enters into the calx, in order ta 
its becoming a metal ? I anfwer, that it unites with a part of 
the inflammable air, and forms nitrous acid ; for the water 
that is collected in this procefs is flrongiy acid, as appears by 
its turning the juice of turnfole red; but the quantity is fo 
fmall, that it will hardly be poffible to afcertain what acid it 
is. Analogy, however, decides clearly in favour of the 
nitrous. 
It may be fuppofed, that in this experiment with red preci- 
pitate, the acid was that which had not been fufficiently ex- 
pelled from that fubftance in the procefs by which it is made- 
But the refult was the very fame when I ufed precipitate per fe ; 
and on this occafion I ufed a portion of that which I procured 
from M. Cadet in Paris, of which mention is made in the 
lecond Volume of my Experiments, p. 36. 
On the other hand, that which is expelled from finery cin- 
der, when it is heated in contact with inflammable air (and 
thereby becomes tronj is pure water , without any acid. This 
1 found to be the cafe even when the inflammable air had been 
got from iron by oil of vitriol. Does not this prove that the 
iron 
