AERO 
iron in the open air by means of a burning lens,, and he 
prefently found that it faturated itfelt with pure air from 
the atmofphere. “ I always found (fays he) that it had 
gained weight in the proportion of 7A to twenty-four. 
The fame was the effect when I melted Heel. But I have 
reafon to think, that with a greater degree of heat than I 
could apply, the iron might have imbibed more than even 
one-third of its original weight.” On attempting to re¬ 
vive the calx of iron in inflammable air, a very unexpected 
appearance took place. Having put a piece of iron fatu¬ 
rated with pure air into a veflel tilled with inflammable 
air confined by water, the inflammable air difappeared and 
the metal was revived; but on weighing it, 2% grains out 
of 11J had been loft, belides the 7 j ounce-ineafures of in¬ 
flammable air which had vanifhed. Confidering all thefe 
circumftances,. the doctor had now no doubt that the two 
kinds of air had united, and formed either fixed air or 
water; and, with a view to determine this point, he re¬ 
peated the experiment in a veflel where the inflammable 
air was confined by mercury, both the veflel and mercury 
having been previoufly made as dry as poflible. In thefe 
eircumflances he had no fooner begun to heat the iron, 
than the air was perceived to diminifti, and at the fame 
time the inlide of the veflel to become cloudy, with parti¬ 
cles of dew that covered alnroft the whole of it. Thefe 
particles by degrees gathered into drops, and ran dowm. 
On collecting this water by means of a piece of filtering 
paper, he found it as nearly as poflible of the fame w eight 
with that which had been loft by the iron ; and alfo that 
the quantity of inflammable air which had difappeared 
was about double that of the dephlogifticated air let loofe 
in the operation. Thus, at one time, a piece of this flag 
abforbed 5$ ounce-meafures of inflammable air, while it 
loft the weight of about three ounce-meafures of dephlo¬ 
gifticated air, and the water collected weighed two grains. 
Another time a piece of flag loll 1 -5 grains, and the water 
produced v as 1-7 grains. J11 a third cafe, where 6J ounce- 
meafures of inflammable air were reduced to 0-92 of a 
meafure, the iron had loft the weight 3-3 ounce-meafures 
of dephlogifticated air, or nearly two grains. 
The doctor, having fucceeded lb well with iron,, next 
tried the calx of copper, and found water produced in the 
inflammable air in the fame manner. On tiling precipi¬ 
tate per /<;, he found no more w ater than might be fuppof- 
ed to have been contained as an extraneous fubftance ei¬ 
ther in the inflammable air, or in the red precipitate. 
With iron, however, the cafe was vaftly different. As 
he had formerly fatisfied himfelf that inflammable air al¬ 
ways contains a portion of water, and alfo that when it 
has been fome time confined by water it imbibes more, he 
repeated the experiment with inflammable air received in 
a veflel of dry mercury; but in this cafe the water was 
produced, to appearance, as copioully as before. “ In¬ 
deed (fays he) the quantity of water produced, fo greatly 
e.vceeding the weight of all the inflammable air, is fuffi- 
cient to prove that it mu ft have had fome other fource 
than any condiment part of that air, or the whole of it, 
together with the water contained in it, without taking in¬ 
to confideraticn the correfponding lofs of weight in the 
iron. 
“ I mull: here obferve, that the iron flag which 1 had 
treated in this manner, and which had thereby loft the 
weight which it had acquired in dephlogiflicated air, be¬ 
came perfect iron as at firft, aud was then capable of being 
melted by the burning lens again ; fo that the fame piece 
of iron would ferve for thefe'experiments as long as the 
operator fliould choofe. It was evident, therefore, that, 
if the iron had loft its phlogifton in the preceding fufion, 
it had acquired it again from the inflammable air which it 
had abforbed ; and I do not fee how the experiment can be 
accounted for in any other way.” Thefe experiments cer¬ 
tainly throw'fome light on the compoiition of.dephlogilfi- 
cated air; and others made by Mr. Cavendifh, Dr. Prielt- 
ley, and the French chemifts, upon water, have a limilar 
tendency. From all of them it is concluded by the. molt 
LOGY. 147 
celebrated philofophers and chemifts, that dephlogiftica¬ 
ted air is one of the conftituent and elementary parts of wa¬ 
ter, inflammable air being the other. 
From the experiments made to afeertain this important 
faft, an account of which may be found in the Philofophi- 
cal Tranfaftions, Mr. Cavendifh draw's the following 
conclufions. He fays—“ There feem two ways by which 
the production of the nitrous acid may be explained: firft, 
by fuppoling that dephlogifticated air contains a little ni¬ 
trous acid, which enters into it as one of its component 
parts ; and that this acid, when the inflammable air is in 
fufficient proportion, unites to the phlogifton, and is turned 
into phlogifticated air, but does not when the inflamma¬ 
ble air is in too fmall proportion ; and, fecondly, by fup- 
pofing that there is no nitrous acid mixed with or entering 
into the compoiition of dephlogifticated air; but that, 
when the air is in fufficient proportion, part of the dephlo¬ 
gifticated air with which it is debated is, by the ftrong af¬ 
finity of phlogifton to dephlogifticated air, deprived of its 
phlogifton, and turned into nitrous acid ; whereas, when 
the dephlogifticated air is not more than fufficient to con- 
fume the inflammable air, none then remains to deprive 
the phlogifticated air of its phlogifton, and turn it into 
acid. If the latter explanation be true, I think we mult 
allow that dephlogifticated air is in reality nothing but dc- 
phlogijlicated water , or water deprived of its phlogifton 
or, in other words, that water conlifts of dephlogifticated 
■air united to phlogifton. On the other hand, if the for¬ 
mer explanation be true, we muft fuppofe that dephlogif¬ 
ticated air confifts of water united to a little nitrous acid, 
and deprived of its phlogifton; but (till the nitrous acid in 
it muft only make a very fmall,part of the whole, as it is 
found that the phlogifticated air into which.it is converted 
is-very fmall in comparifon of the dephlogifticated air. I 
think the fecond of thefe explanations feems'much the more 
likely; as it w'as found that the acid in the condenfed li¬ 
quor was of the nitrous kind, not only when the dephlo¬ 
gifticated air was prepared from nitrous acid, but when 
procured from plants or turbith mineral. Another ftrong 
argument in favour of tills opinion is, that dephlogifticated 
air yields no nitrous acid when phlogifticated by liver of 
fulphur; for if this air contains nitrous acid, and yields - 
it when phlogifticated by explofion with inflammable air, 
it is very extraordinary that it fliould not do fo by other 
means. But what forms a ftronger, and, I think, almoft 
decifive, argument in favour of this explanation, is, that, 
when the dephlogifticated air is very pure, the condenfed 
liquor is made much more ftrongly acid' by mixing the air 
to be exploded with a little phlogifticated air.” 
'Fhe whole of Dr. Prieftley’s opinions on the component 
parts of this kind of air, are dimmed up thus—“The only 
kind of air that is now thought to be properly elementary y 
and to eonfift of a Ample fubftance, is dephlogifticated air;: 
with the addition at leaft of the principle of heat, concern¬ 
ing which we know very little; and, as it is not probable 
that this adds any thing to the weight of bodies, it can 
hardly be called an element in their compoiition. Dephlo¬ 
gifticated air appears to be one of the elements of water,. 
of fixed air, of all the acids, and many other ftibftances, 
which, till lately, have been thought to be Ample.” 
The experiments of the French philofophers were of 
the fame nature with thofe of .Mr. Cavendifh, but con- 
dlifted on a larger feale. The inference drawn from them 
was the fame with that already mentioned, viz. that de¬ 
phlogifticated andinflammable aii in all cafes are the two 
conftituent parts of w ater. This opinion is aliaadopteda 
by Mr. Kirwan in his Treatife on PhlogiJlonj. 
Notwithftanding thefe pofitive conclufions, however, by 
fome of the 1110ft refpeftable men in this country, the evi¬ 
dences adduced have been unfatisfaftory to fome French 
chemifts, who maintain, that Meflrs. Cavendifh, Prieft- 
ley, and Kirwan, are totally mil taken with regard to the 
production of water from dephlogifticated and inflamma¬ 
ble air; and contend that the water obtaiired had previ- 
oully exiftedin the air, and was not originally produced in, 
