Acidity , the Compojltion of Water , and Phlogi/lon, 157 
oxygenous principle may be given to that thing which, when it 
is incorporated with water, makes dephlogifticated air. 
As there is fomething in dephlogifticated air that feems to 
be the principle of univerfal acidity , fo I am hill inclined to 
think, as I obferved in my laft Volume of Experiments, that 
phlogifton is the principle of alkalinity , if fuch a term may be 
ufed ; efpecially as alkaline air may be converted into inflam- 
mable air. 
I11 the courfe of experiments recited in this Paper, I difco- 
vered more completely than before the fource of my former 
miftake, in fuppofing that fixed air was a neccflary part of the 
produce of red lead, and alfo of manganefe. Both thefe fub- 
lfances, I And, give of themfelves only dephlogifticated air, 
and that of the pureft kind ; and all the fixed air they yielded 
in my former experiments mud have come from the gun- 
barrel I then made ufe of, which would yield inflammable air, 
which, with dephlogifticated air, forms fixed air. For though 
the dephlogifticated air from red lead was fo pure that, mixed 
with two meafures of nitrous air, the three meafures were 
reduced to five hundredth parts of a meafure, and the fub- 
ftance gave no fixed air at all when it was heated in an earthen 
tube or retort ; yet by mixing iron filings with it, or with mail' 
ganefe, as I had formerly done with red precipitate, I got more 
or lefs fixed air at pleafure, and fometimes no dephlogifticatecL 
air at all. 
