AERO 
fame goodnefs with common air. Hence he draws the fol¬ 
lowing conclufions:— i: That five-fixths of the air we 
breathe are mephitic, or incapable of fupporting the ref- 
pirationof animals, or the inflammation or combuftion of 
bodies. 2. That the furplus, or only one-fifth of the vo¬ 
lume of atmofpherical air, is refpirable. 3. That, in the 
calcination of mercury, this metallic fubftance abforbs 
the falubrious part, leaving only the mephitic portion of 
the air. 4. That by re-uniting thefe two portions which 
had been feparated, we can recompound air fimilar to that 
of the atmofphere. 
To determine the effects of refpiration upon air, a live 
fparrow was placed under a glafs receiver, filled with 
common air and inverted in mercury, containing thirty- 
one cubic inches. In a quarter of an hour it became agi¬ 
tated, and in fifty-five minutes died convulfed. Notwith¬ 
standing the heat of the animal, which neceffarily, atfirft, 
rarefied the air in the receiver, there was a fenlible dimi¬ 
nution of its bulk; which, at the end of fifteen minutes, 
amounted to one-fortieth: but, inftead of increafing af¬ 
terwards, the diminution became fomething lefs in about 
half an hour; and, when the animal was dead, and the 
air in the receiver had recovered the temperature of the 
room where the experiment was made, the diminution 
did not appear to exceed one-fixtieth part. This air, 
which had been refpired by the fparrow, though in many 
refpetls fimilar to that in which the mercury had been 
calcined, differed from it in this refpect, that it precipi¬ 
tated lime-water, and, by introducing cauftic fixed alkali 
to it, was reduced one-fixth in bulk by the abforption of 
fixed air; after which it appeared exactly the fame with 
that produced by the calcination of mercury or other me¬ 
tals; and atmofpherical air was recompofed by mixing 
tins with pure dephlogifticated air in the proportions al¬ 
ready mentioned. 
It appears from the experiments of Scheele and many 
other chemiffs, that the doftrine of phlogifton has been 
carried too far by our Britifh philofophers, and that the 
air confifts of two kinds of fluids; one friendly in the 
higheft degree to animal life; the other altogether unfit 
for it. Thefe two appear incapable of being converted di- 
reflly into one another by any procefs, natural or artificial: 
for, though both are deftruffible, yet they are always con¬ 
verted into other fubffances; from which, indeed, either 
the one or the other may be extracted at pleafure. 
The ftrongeft arguments in favour of the tranfmutation 
of phlogifticated air into that of a purer kind, were drawn 
from the purification of noxious air by vegetation, and by 
agitation in water. In the former cafe, however, as has 
been obferved, this feeming purification is no other than 
an exchange of the o.ne air for the other; the vegetables 
abforbing the phlogifticated, and emitting the dephlogifti¬ 
cated air in its ftead. With refpedf to the agitation in wa¬ 
ter, matters, remained more dubious till the difeovery 
made by Dr. Prieftley, of the emiffion of pure air from 
the latter, and of the pofiibilit-y of-air within a-jar being 
influenced by the atmofphere through a body of water 
twelve inches in depth. Thefe remarkable faffs were il- 
luftrated by the following experiments:—x. About three 
ounce-nreafures of air, phlogifticated by nitrous air, were 
agitated for a quarter of an hour in a veil'd containing 
twenty ounces of water, which had been boiled for feve.- 
jal hours, and which was ftill very warm. By this pro¬ 
cefs it became diminiftied one-fixth, and confiderably im¬ 
proved in quality. The next day the remainder was agi¬ 
tated lor another quarter of an hour, and the water which 
was boiled at the lame time, when it was alfo diminiftied 
in quantity and improved in quality. 2. An equal quan¬ 
tity of air, phlogifticated by means of iron-filings and 
brimftone, being agitated for twenty minutes, was dimi- 
nifhed by one-fieventh, and improved fo far that a candle 
would burn in it. 3. After expelling all the air he could 
from a quantity of water by boiling, he put to it, in fe- 
parate vials,, air that had be.en phlogifticated with iron-fi¬ 
lings and brimftome, as well as that which the heat had 
Vol. I. No. 10. 
L O G V. r 49 
expelled, leaving them with their mouths in water, and 
agitating them occafionally. On examining the-vials in 
about two months, he found both the air that was con¬ 
fined by water, and that which had been expelled by heat, 
completely phlogifticated. 4. That water does imbibe the 
purer part of the atmofphere, in preference to that which 
is impure, is evident, he fays, from an examination of it: 
for, if the water be clear, and free from any thing that is 
putrefeent, the air expelled from it by heat is generally 
of the ftandard of one ; whereas that of the atmofphere, 
when the nitrous air is the pureft, is about 1-2. 
Phlogifticated air is equally inviiible with common air, 
and fomething more elaftic. It is fatal to animal life, and 
friendly to that of vegetables. It feems to exift originally, 
in very large quantity, in our atmofphere, from whence 
it may be feparateft by combuftion, by refpiration, by pu¬ 
trefaction, and by every fpecies of plilogiftic procefs. 
Any other fpecies of air may be converted into this by 
means of fire, dephlogifticated air alone excepted. Phlo¬ 
gifticated air is now' generally believed to be a combina¬ 
tion of the nitrous acid with phlogifton ; and tluit, in its 
gradual progrefs towards this, which is its ultimate ftage, 
it firft affix mes the character of phlogifticated nitrous acid ; 
then of nitrons air, in which it readily parts with its phlo¬ 
gifton to the atmofphere, or father to the dephlogifticated 
part of it; and, laftly, it becomes phlogifticated air, in 
which the union betwixt the principles is fo ltrong, that it 
cannot be broken by Ample expofure to dephlogifticated 
air without heat; though the experiments of Mr. Caven- 
difti {hew, that this may be done by means of the eleCtric 
fpark, which produces the molt violent heat we can ima¬ 
gine. 
It had been frequently obferved, that common atmof¬ 
pherical air was always diminiftied by taking the eleCtric 
fpark in it; and this diminution was fuppofed to be occa- 
fioned by the phlogiftication of the air, and feparation of 
its fixed part; in confequence of which it was urged, that 
lime-water is precipitated by taking the eleCtric fpark 
over it in a fmall quantity of air. Mr. Cavendilh, how¬ 
ever, who has carefully examined this fubjeCt, denies that 
any fixed air is produced in this manner: and, by a fet of 
very curious experiments, publifhed in the 75th volume 
of the Philofophical TranfaCtions, has clearly (hewn that 
nitrous acid, and not fixed air, is the produCt of this ope¬ 
ration. 
As in fome former experiments Mr. Cavendilh had 
found, that, by deflagrating nitre with charcoal, the whole 
of the acid was converted into phlogifticated air, he con¬ 
cluded that this kind of air is nothing elfe than nitrous 
acid united to phlogifton; according to which, it ought to 
be converted into nitrous acid by being deprived of its 
phlogifton. But (lays he) as dephlogifticated air is on¬ 
ly water deprived of phlogifton, it is plain, that adding 
dephlogifticated air to a body is equivalent to depriving it 
of phlogifton, and adding water to it; and therefore phlo¬ 
gifticated air ought alfo to be reduced to nitrous acid by 
being made to unite or form a chemical combination with 
dephlogifticated air; only the acid tints formed will be 
more dilute than if the phlogifticated air were (imply de¬ 
prived of phlogifton. 
“ This being premifed, we may fafely conclude, that, in 
the prefent experiments, the phlogifticated air was ena¬ 
bled, by means of the electrical fpark, to unite to, or form 
a chemical combination with, the dephlogifticated air, and 
was thereby reduced to nitrous acid, which united to the 
foap-leys, and formed a folution of nitre ; for, in thefe 
experiments, the two airs actually difappeared, and nitrons 
acid was formed in their room: and, as it has been fhewn, 
from other circumftances, that phlogifticated air mu ft form 
nitrous acid when combined with dephlogifticated air, the 
above-mentioned opinion feems to be fufficiently eftablifh- 
ed. And a further confirmation is, that no diminution of 
air is perceived when the eleftric fpark is palled either 
through pure dephlogifticated or through perteftly 
phlogifticated air; which indicates a neceffity for the com- 
Q^_q bination 
