AERO 
not kindle pyrophorus, though the nitrous air from which 
it is produced inftantly fets it on fire. 
Of Vitriolic, Nitrous, Marine, and other, Acid Airs. 
Of Vitriolic Acid Air. This is always a combination of 
vitriolic acid with phlogifton, and cqnfequently may be 
produced from any .mixture of that acid in its highly con¬ 
centrated-ftate with phlogiftic matter. Hence all the me¬ 
tal? yield it, gold and platina excepted, on boiling them 
with ftrong vitriolic acid, which itfelf will produce it 
when rendered black by any phlogiftic matter. To expel 
this kind of air the flame of a candle is fufflcient. It is 
the heavieft of all except fluor acid air, being tc common 
air as 2265 to 1000. Dr. Prieftley afferts, that a quantity 
of vitriolic acid thus impregnated with phlogifton will 
yield many times more air than an equal quantity of the 
ftrongeft fpirit of fait. When the vitriolic acid air is 
produced in great plenty, the top of the vial in which it 
is generated is commonly filled with white vapours. The 
air has alfo the fame, appearance as it is tranfmitted through 
the glafs tube ; and it is fometimes difCoyerable in the re¬ 
cipient. It is rnoft equably produced by tiling ftrong vi¬ 
triolic acid and charcoal; but the production of this kind 
of air is moftly attended with that of inflammable, and 
fometimes fixed or phlogifticated, air. With ether about 
one-half of the firfl produce is inflammable; but the 
quantity leflens as the procefs goes on. Copper, lilver, and 
lead, when heated in vitriolic acid, yield the pureft vitrio¬ 
lic acid air; but lead yields only a fmall quantity, and 
requires a great heat. It is procured in the greateft abun¬ 
dance from the fumes of burning fulphur, and is then 
called the volatile vitriolic or Julphureous acid. 
Of Nitrous Acid Air. This is the pure nitrous acid by 
itfelf, without any addition of phlogifton. It is procured 
by heating the ftrong fpirit of nitre in a vial, and receiv¬ 
ing the vapour in glafs veflels filled with quickfilver. It 
is difficult, or rather impollible, to preferve it for a length 
of time, by means of any fluid. Water abforbs it im¬ 
mediately, and quickfilver is corroded, and produces ni¬ 
trous air. 
The mod remarkable property of this vapour is, that 
its colour may be more or lefs heightened by the mere 
circumftance of heat; the intenfity of colour diminilhing 
as it becomes cool. “ It feems probable (fays Dr. Prieft¬ 
ley), that if this vapour was not confined, but had room 
to expand itfelf, it would become colourlefs with heat. 
This at leaft is the cafe when it is combined with water. 
The phenomena 1 refer to are very common in the pro¬ 
cefs for making dephlogifticated air, in which I firft ob- 
ferved them. But the fame things are obfervabie in the 
procefs for producing any other kind of air in which much 
fpirit of nitre is made ufe of; and likewife conftantly 
in the common procefs for making fpirit of nitre itfelf. 
It is, that, u'hen the heat is moderate, the vapour within 
the glafs tube or retort is red ; but that, as the heat in¬ 
creases, it becomes tranfparent.” The dodtor having ob- 
ferved that red lead impregnated with nitrous vapour loft 
its red colour and became white, “ I put (fays he) a fmall 
quantity of this white minium into a glafs tube doled at 
one end; then, holding it to the fire, make it emit the red 
vapour till the whole tube is filled with it; and, having 
the other end of the drawn out ready for clofing, as foon 
as the vapour begins to ifflie out of that end I apply my 
blow-pipe and feal it. By this means I conclude that the 
tube is filled with a pure red vapour, without any mix¬ 
ture of nitrous air, and perhaps common air alfo.” 
Oj- Marine Acid Air. The marine acid, by heat, may be 
refolved into a permanently-elaftic and tranfparent inviii- 
bie vapour, which, not acting on quickfilver, is more ea- 
fdy preferved than nitrous acid air. It is eafily and cheap¬ 
ly obtained by filling a vial, fitted with a glafs tube and 
Hopper, with common fait, and then pouring a fmall 
quantity of vitriolic acid upon it; which, by the affiftance 
of heat, will difengage the acid principle, or the marine 
acid air, from the fait. A vial thus prepared will iuilice, 
LOGY. 159 
for common experiments, many weeks; efpecially if fre/h 
vitriolic acid be occalionally put to it. It only requires a 
little more heat at the laft than at the firft. After all the air 
is expelled, it is fo weak as barely to corrode iron. The 
gas itfelf is to common air as five to three; a cubic inch 
weighing 0-654 grains. It is very fatal to animal life, but 
lefs fo than pure nitrous air. On dipping a candle into it, 
the flame is extinguifned ; but the moment before it goes 
out, and when it is afterwards lighted again, it burns 
with a green or light-blue flame, like that of common 
fait thrown into a fire. Its diminution by the eledtric 
fpark is barely perceptible. Ice is diffolved by it as faff: 
as by a red-hot iron. It is partly abforbed by almoft eve¬ 
ry lubftance containing phlogifton, and the remaining part 
becomes inflammable. Oil of olives abforbs it very flow, 
ly, and oil of turpentine very faft; by which they both 
become almoft black, and the remainder of the air is in¬ 
flammable. Eflential oil of mint abforbs marine air pret¬ 
ty faft, becoming brown, .confident, and fo her. />. is to fink 
in water; and its fmell is in great meafure altered. Ether 
abforbs it very faft, the mixture becoming firft turbid, 
then yellow, and at laft brown. The air over the ether 
is ftrongly inflammable, A fmall bit of phofphorus 
fmoked and gave light in this acid air; and the elaftic fluid 
w-as but little diminilfied in twelve hours. About four- 
fifths of the gas were ablorbed by water, arid the reft was 
inflammable. This change was alfo eff ected by a number 
of other lubftances ; forne of which, however, required a 
confiderable time to produce their effedt. 
Of Fluor Acid Air. Mr. Scheele firft obtained this kind 
of air by diftilling the fpar called fluor with vitriolic acid. 
Dr. Prieftley, who made feveral experiments upon the 
fubjedt, was of opinion that this new acid was only the 
vitriolic difguifed by its connection with the fluor. He 
even fuppofed that he had produced it by pouring vitrio¬ 
lic acid on other phofphoric fpars: both thefe opinions, 
however, he has now retradted, and believes the fluor 
acid to be one of a peculiar kind. Its rnoft remarkable 
property is the great attradlion it has for filiceous earth, 
fo that it even corrodes and makes holes in the retorts' in 
which it is diftilied. Some curious etchings on glafs have 
been performed by it. 
Of the Vegetable and another Acid Air. By the help of 
heat alone," the concentrated vegetable acid emits a per¬ 
manently-elaftic and aerial fluid. This has the properties 
of the acid of vinegar; but, like it, is weaker than the 
mineral acid airs, though fimilar in its general charadters. 
Water imbibes it as readily as any of the other acid airs; 
olive-oil abforbs it in confiderable quantity, lofing at the 
fame time its yellowilh colour. Common air is phiogifti- 
cated by it, as by the liquid vegetable acid.. As the ve¬ 
getable acid, however, from which this air had bpen ob¬ 
tained, was diftilied with oil of vitriol, it may rather be 
vitriolic than vegetable acid air. 
A new kind of acid air was obtained by Dr. Prieftley 
from diftilling to drynefs a folution of gold in marine acid 
impregnated with nitrous acid vapour, which makes the 
bell kind of aqua regia. The produce was an acid air 
partaking both of the nature of the nitrous and marine 
acids; but more.of the latter, as it extinguilhed a candle, 
w’hich exhibited a rnoft beautiful deep blue flame, and on 
being dipped into the fame jar went out more than twenty 
times fucceflively, making a very pleafing experiment. 
The quantity of this acid air is very great; and the refi- 
duum fometimes dephlogifticated, fometimes phlogiftica- 
ted, and at other times nitrous, air. 
To the article Chemistry we refer for other particu¬ 
lars relative to the different kinds of air here fpoken of. 
Of Hepatic Air. 
This fpecies of air was firft obtained by Mr. Bergman, 
from an ore of zinc called Pfcudogalena nigra Danncmoren - 
fis. It was produced, .but in fmall quantity, from vitrio¬ 
lic acid poured on this mineral. Spirit of fait yielded it 
in much larger quantity; but nitrous acid produced only 
nitrous 
