156 AERO 
.by the eleitric fpark. Very pretty artificial fires are alfo 
made, with glafs tubes bent in various direftions, and 
pierced with a great number of fmall apertures. The in¬ 
flammable gas is prefled forward into thefe tubes, from a 
bladder, and the inflammable air, ifluing out of all the 
fmall apertures, is fei on fire by a lighted taper. None 
of thefe contrivances, however, has proved of anyufe; 
and the fchemeof Mr. Voita, for fubftituting its explofive 
force inllead of gunpower, is found infufficient. 
Sulphurated Inflammable Air. 
This was difcovered by Dr. Prieflley at the time he was 
engaged in tranfmitting (team through red-hot tubes con¬ 
taining fome folid material. Having treated manganefe 
in this manner, by flopping one end of the heated tube with 
a cork before the fleam was applied, he received forty 
ounce-meafures of air, of which one-fixth was fixed air, 
and the red of theftandard of x -7, lambently inflammable. 
Having then opened the other end of the tube in order to 
admit the fleam, air was produced more copioufly than be¬ 
fore. Of fifty ounces of this air, one-feventh was fixed, 
and the reft, of the ftandard of 1 - 8, explolively inflamma¬ 
ble. The lalt portions were very turbid; and the fmell, 
efpecially that of the laft portion, was very fulphureous, 
tinging the water of a very dark colour, by depofiting in it 
a quantity of blackifh water. However, the air itfelf be¬ 
came prefently tranfparent; but on looking at the jar in 
about ten minutes after, it was quite black and opaque ; fo 
that nothing could be feen in the inlide of it. Filling af¬ 
terwards another jar with the fame kind of air, in order to 
obferve the progrefs of this uncommon phenomenon, he 
found, that when the water was well fubfided, black (pecks 
began to appear in different places, and, extending them- 
lelves in all directions, at length joined each other, till the 
whole jar was become perfectly black, and the glafs opaque. 
When this was done, he transferred the air into another 
jar; and it foon produced a fimilar effeCt upon this, though 
it never became fo black as the jar in which it had been 
firft received. It alfo frequently happened, that only the 
lower part of the jar would become black, as if the matter 
with which it was loaded had kept fubfiding, though in- 
vifibly, in the rnafs of air, and occupied only the lower re¬ 
gions, leaving the upper part entirely free from it. On 
expofing to the open air the vefl'els thus turned black, the 
colour prefently difappeared, and a yellow or brown in- 
cruftation was left upon it.—Other fpecimens of manga¬ 
nefe produced no air of this kind ; but iron that had been 
melted in vitriolic acid air yielded it readily. Diflblving 
this with a confiderable quantity of freflt metal in diluted 
vitriolic acid, he found that the water in which the air 
was received became very black, anddepofited more fedi- 
ment than in the experiment with manganefe. On burn¬ 
ing a quantity of it, this kind of air appeared to contain 
fome vitriolic acid ; but, on decompofing it with dephlo- 
gifticated air, the diminution was exaftly the fame as when 
common inflammable and dephlogifticated air were ufed ; 
only there was a fmall quantity of fixed air produced, 
which is never the cafe with common inflammable air 
from vitriolic acid and iron. 
Of Alkaline Air. 
This was firft procured by Dr. Prieflley, who obtained 
it by mixing one part of pounded fal-ammoniac with three 
parts of flaked lime. When pure, it is inftantly fatal to 
animal life, and extinguifties flame ; though, when mixed 
with atmofpheric air, it is (lightly inflammable. A can¬ 
dle dipped into this air is extingui(hed ; but, juft before 
the flame goes out, it is enlarged by another flame of a pale 
yellow, and fometimes a weak flame fpreads for a confi¬ 
derable way, or even through the whole body of the al¬ 
kaline air. Electric fparks taken in it appear of a red 
colour, augment its bulk, and by degrees turn the whole 
into inflammable air. It is readily abforbed by water, 
and diftblves ice almoft as faft asan hot fire. On confining 
fome water impregnated with alkaline air in a glafs tube, 
LOGY. 
and expofing it to a ftrong heat for fome days, a white 
pellicle or incruftation formed on its furface. Bits of li¬ 
nen, charcoal, and fponge, admitted into alkaline air, di- 
minifhed it, and acquired a very pungent fmell; efpecially 
the fponge, a bit of which about the fize of an hazle-nut 
abforbed an ounce-meafure. It is remarkable that cop¬ 
per, which is fo eafily corroded by the common volatile 
alkalies, is not attested by alkaline air. Its fpecific gravi¬ 
ty Mr. Kirwan determines to be to that of common air as 
600 to 1000 ; though this differs confiderably according to 
the moifture it contains. 
Inprofecuting hiscxperimentsonalkaline air, Dr. Priefl¬ 
ley concluded that it contains phlogifton, both from its 
being convertible into inflammable air by eleftric explo- 
fions, and likewife from its reviving the calces of metals. 
In attempting to afcertain the proportion of lead revived 
in alkaline air, he found fix grains of lead in three ounce-- 
meafures, fixteenand a half in three and a half meafures, 
thirteen in two and a half, and twelve in three and three 
quarters ; but the experiment on which he laid the great- 
eft ftrefs, was that in which twenty-fix grains and a half of 
lead were revived in feven and a half ounce-meafures of 
alkaline air. In this proportion, 100 ounce-meafures of 
alkaline air would revive 3 52 grains of lead; but an equal 
quantity of inflammable air from iron w ould have revived 
480 grains of metal. This deficiency appeared fomewhat 
furprifing, fince alkaline air is refolved into more than 
twice its bulk of the inflammable kind ; though pofiibly 
inflammable air from iron may contain more phlogifton 
than that into which alkaline air is refolvable.—On heating 
red precipitate in alkaline air, the .mercury was revived 
as in other cafes, and a confiderable quantity of water 
produced, though none appeared on reviving it with com¬ 
mon inflammable air. 
In examining the phenomena which attend the conver- 
lion of alkaline air into the inflammable kind, the dodtor 
was induced to believe that it was occafioned by heat alone, 
without the concurrence of light. The effects of the for¬ 
mer were firft perceived on heating fome ochre of iron in 
alkaline air; when, though the matter turned black, as 
in an incipient reduction of the metal, he found a confi¬ 
derable increafe of quantity, infteadof decreafe, in the air, 
as he had expected ; and, on examining the quality of it, 
he found that it contained no fixed air, but was entirely 
inflammable. In all his experiments, however, with a 
burning-glafs, as a ftrong light was concerned, he heated a 
quantity of alkaline air in a green glafs retort, receiving in 
a glafs tube, filled with water, all the air that could be ex¬ 
pelled from it by heat. At firft it was all abforbed by the 
water, being merely alkaline air expelled by the rarefac¬ 
tion ; but, when the bulb of the retort became red-hot, he 
found that the bubbles driven out were not wholly abforb¬ 
ed, and at laft none of them were fo. Thefe were alto¬ 
gether inflammable; fo that no doubt remained of the 
change being produced by heat alone, without any inter¬ 
vention of light. 
It was farther obferved, that, whenever the alkaline air 
was changed into inflammable by means of bits of retorts 
or crucibles containing clay, they always became black 
during the procefs. He therefore fuppofed, that fotne- 
thing might be depofited from the air upon the clay. 
“ Indeed (fays he), if this was not the cafe, I do not fee 
why the clay ftiould become black; though, perhaps, 
part of the fame phlogifton which forms the inflammable 
air may be attracted by the red-hot clay, without there 
being any proper decompolition of the air. That this is 
the cafe feems probable from an experiment in which I 
ufed porcelain inftead of common earthen ware ; which 
did not become black in the procefs, though inflammable 
air was produced.” 
In fome of Dr. Prieftley’s experiments, he had obferv¬ 
ed that iron which had long rufted in nitrous air gave out 
a ftrong fmell of volatile alkali. This extraordinary phe¬ 
nomenon, however, was only perceived where the nitrous 
air and iron had been in contadt for a very long time ; but 
he 
