Acidity , the Decompofltion cf IV ater, and Phlogijlon, 3 1 7 
iron had imbibed what was properly water , and not any one 
conftituent part of water only ? 
That water enters into the conftitution of every kind of air 
I fuppofed, becaufe it certainly does into that of inflammable 4 
fixed, and dephlogifticated air, and becaufe none of them can be 
produced except by procefles in which water either certainly is, 
or may be well fuppofed to be, prefent. That nitrous air alfo 
contains water, I have lately found from the iron that is heated 
in it becoming a proper finery cinder. 
At the publication of my lad: Volume of Experiments, I 
had found, that iron heated in nitrous air acquired weight, 
and that what remained of the air was phlogidicated air. 
Having fince that time repeated this experiment, and after- 
wards heated the iron, which was by this means increafed in 
weight, in inflammable air, the iron lofl: its additional weight, 
and water was copioufly produced, as in the fame procefs with 
finery cinder, or, as I fometimes call it, fcale of iron. 
As nitrous air may be deprived of its water, and become 
phlogifticated air by heating iron in it, I find that it undergoes 
the fame change by being repeatedly tranfmitted through hot 
porous earthen tubes, through which I fome time ago difco- 
vered that vapour will pafs one way, while the air contiguous 
to the heated tube will pafs the other. 
I firft tried this procefs with turnings of iron in the tube, 
by which means the iron was readily converted into finery cin- 
der ; but afterwards I found that the fame change was produced 
in the nitrous air by the hot tube only. The two bladders 
which I made ufe of in this experiment (and by the alternate 
preflure of which I made the air contained in them pafs 
through the hot tube) became red , juft as any bladder does 
that is filled with nitrous air, and then expofed to the influ- 
U u 2 ence 
