2 20 Continuation of the Experiments and Ohfervations 
found different from common air (lightly injured. Accordingly, 
we find that this conjedfure, firff advanced by Dr. triestley 
in the infancy of his refearches, is now abandoned by him. 
Vol. V. p. 31. And he now juffly thinks, that common air 
does not contain above of its bulk of fixed air. 
As to the diminution of bulk, it is certain, that the whole of 
it does not proceed from the feparation of fixed air ; for though 
no part of the fixed air (hould be abforbed, yet fince part of the 
common air is converted into fixed air, there muff be a diminu- 
tion of bulk, fince fixed air is fpecifically heavier than common 
air, and the bulks are inverfely as the fpecific gravities ; but the 
diminution of mafs muff wholly, and that of bulk muff alfo 
for the greater part arife from the abforption of fixed air by 
water, or the fubffance from which the phlogiffon proceeds. I 
have fucceflively added fix meafures of nitrous air to two of 
dephlogifficated air from precipitate per fe, and after each addi- 
tion transferred the mixture into frefh lime-water, and after 
each I found the lime precipitated until the whole was reduced 
to one-tenth nearly, fo that nine-tenths of this dephlogifficated 
air was evidently converted into fixed air j and Imce fixed air 
did not pre-exiff in the dephlogifficated air, it was evidently 
produced by the union of the phlogiffon of the nitrous air with 
the truly dephlogifficated part of the dephlogifficated air. 
Here we fee how fixed air is generated in moff other phlo- 
giffic proceffes, performed in common air. The phlogiffon is 
attra&ed by the dephlogifficated part of common air, unites to 
it, expels part of its fire, and fo forms fixed air ; yet a part of 
this pure air generally efcapes the aflion of phlogiffon, being 
prote&ed from it by the quantity of phlogifficated air which is 
always found in common air, and which forms about two- 
thirds of it, in the fame manner as gold is prote&ed by 
fiilver, 
