This gas is much heavier than atmospheric 
air. It gives the same signs of acidity as the mu- 
riatic acid itself; and this indeed ought to be 
the case, as it is the same substance, it reddens 
blue vegetable colours, but it destroys neither 
them nor any of the other colours, as the oxy- 
genated muriatic gas does. 
It combines with all the alkaline bases, and 
forms with them muriatic salts. If it is mixed 
with ammoniacal gas, it combines with it, and 
forms muriate of ammonia. 
It suffocates animals immersed in it, and 
extinguishes a lighted taper ; but it iirst en- 
larges its flame, and makes it appear of a green 
or bluish colour at the edges. 
Oxygenated muriatic acid gas. 
The dephlogisticated muriatic acid of Scheele, 
under a gaseous form, is the muriatic acid gas 
surcharged with oxygen. 
This gas is obtained by exposing the mu- 
riatic acid to heat and evaporation, whilst it is 
acting on a substance which contains oxygen ; 
such, for example, as the native oxyd of man- 
ganese: if you therefore put black oxyd of 
manganese and muriatic acid into a glass re- 
tort, and expose them to heat, a strong fer- 
mentation will be excited, during which the 
muriatic acid will be converted iirto gas, but 
surcharged with oxygen, which is taken from 
the oxyd of the manganese, because it has a 
greater affinity for that substance. 
It may In* prepared in the water apparatus, 
though it is absorbable by water, if care is 
taken to fill the bells, or air-jars, completely 
with the gas, and to leave no water in them. 
Oxygenated muriatic gas is not invisible, 
like the other gases ; it is of a greenish yel- 
low colour, which renders it very percep- 
tible. 
This gas destroys vegetable colours entire- 
ly. Ah flowers, and the green leaves of 
plants, are rendered white by it, and alkali is 
not capable of restoring their colours. 
This effect can only be ascribed to the ab- 
sorption of oxygen. This gas, which contains 
oxygen in excess, gives up a part, which ve- 
getable substances absorb with avidity, and 
by this absorption lose their colour. The ox- 
ygenated muriatic acid gas then becomes con- 
verted into common muriatic acid gas. 
This property lias given rise to a new 
method of bleaching, which has proved 
successful. The application of the oxyge- 
nated muriatic acid, either in the gaseous 
or the liquid state, has assisted the process 
of whitening thread, cotton, linen, wax, &c. 
in a surprising degree, and it is now very 
generally employed for this purpose. 
To shew its effects in bleaching, suspend 
some-unbleached calico, or linen, moistened 
with water, in a jar filled with the gas; the 
natural colour of the cloth will soon begin to 
fade, and at last totally disappear. If different 
coloured patterns Of printed calico are im- 
mersed for a few minutes in the gas, their co- 
lours will soon be destroyed, except those 
which are yellow. 
Though oxygenated muriatic acid gas is ex- 
ceedingly noxious to life, it does not extin- 
guish combustion. If a burning taper, fixed 
to a wire, is immersed in it, the taper burns 
of a red colour, 'and more vividly than in at- 
mospheric air ; a greater quantity of smoke is 
emitted at the. same time. 
Fill a tall receiver, furnished with a ground 
stopper, with oxygenated muriatic acid gas 
over water, and let fall into it copper, in thin 
AIR BALLOON. 
leaves, called Dutch gold. The leaf, before | 
it reaches the bottom of the receiver, will 
burn with a pale green light. 
Gold leaf may be burnt in the same man- 
ner. Copper wire, when heated to redness, 
also takes fire when introduced into the gas in 
that state. 
Fluoric acid gas. The radical of fluo- 
ric acid gas is unknown. It may be obtained 
by decomposing fluate of lime (Derbyshire 
spar), by means of sulphuric acid. For this 
purpose, put one part -of powdered fluate of 
lime into a leaden retort, and pour over it two 
or three parts of sulphuric acid. A violent 
action ensues, and fluoric acid gas is extri- 
cated, which must be collected over mercury, 
either in a leaden or tin vessel, or in a glass 
receiver covered within with a coat of var- 
nish or wax. When no more gas is produced, 
the action of the acid must be assisted by a 
gentle heat. 
The most remarkable property of this gas 
is its power of dissolving silex : it therefore 
dissolves glass crystals, and various precious 
stones. It is heavier than common air. It 
does not maintain combustion, nor can ani- 
mals breathe it. It is absorbed by water, and 
forms with it liquid fluoric acid. It has a pe- 
netrating odour. It corrodes animal and ve- 
getable substances. Light has no effect upon 
it. It emits white fumes, when in contact 
with moist atmospheric air. It reddens blue 
vegetable colours. With ammonia, it forms 
a concrete body. It has no action upon pla- 
tina, gold, silver, mercury, tin, lead, antimo- 
ny, cobalt, nickel, or bismuth ; but it corrodes 
iron, arsenic, and manganese. 
The property of dissolving silex has caused 
it to be applied to etching on glass, which is 
done either by means of the fluorid acid gas, 
or liquid fluoric acid. 
AIR BALLOON, a general name given 
to bags or other light substances filled with an 
aerial fluid. The art of Hying, or of imi- 
tating the feathered tribe, lias long been the 
object of earnest desire amongst men. Cars, 
artificial birds, wings, and other mechanisms 
for flying, generally absurd, and always in- 
sufficient, have frequently been exhibited to 
the undisfinguishing eye of the vulgar; but 
the strictest enquiry into the accounts of au- 
thentic history, finds no mention of any suc- 
cessdsaving ever attended the attempts of this 
nature, previous to the year 1782. The re- 
cent discoveries made on the nature and pro- 
perties of aerial fluids, by the industry of 
Black, Priestley, Cavendish, and others, sug- ; 
gested, some time before the above-mention- 
ed year, the practicability of forming machines 
sufficient to elevate considerable weights into 
the regions of the atmosphere. Mr. Cavendish 
was the first who ascertained the specific gra- 
vity of hydrogen gas (then called inflammable 
air) and found it to be a vast deal lighter 
than common air. His experiments on 
this subject are published in the Philosophical 
Transactions for the year 1766. In conse- 
quence of this discovery, it was natural to 
conclude, that if a large bladder, or other en- 
velope, was filled with hydrogen gas, and 
that if the weight of file envelope added to 
that of the contained gas, was less than the 
weight of an equal bulk of common air, the 
apparatus would mount up into the atmo- 
sphere for the same reason, and in the same 
manner, as a cork would rise from the bot- 
tom towards the surface of the sea, suppos- 
ed 
j ing riie cork was left at liberty in the for- 
mer place. 
Dr. Black of Edinburgh thought of filling 
the allantois of a calf with hydrogen gas, for 
the purpose of shewing at his lectures that 
such a body would ascend into the atmo- 
sphere ; but he never put tiie project to the 
test of actual experience. 
Early in the year 1782 Mr. Cavallo made 
the first attempts to elevate a bag full of hy- 
drogen gas into the surrounding air, and an 
account of his experiments was read at a 
meeting of the Royal Society on the 20th of 
June, 1782. 
The weight of hydrogen gas, the mean 
weight of atmospherical air, and the weight 
of the substance of which the vessel or bag 
is to be formed, being ascertained, it is easy 
from those particulars to determine by calcu- 
lation the dimensions of a vessel, which, 
when filled with hydrogen gas, might be 
lighter than an equal bulk of common air. 
Upon this principle Mr. Cavallo tried blad- 
ders, the thinnest and largest that could be 
procured. Some of them were cleaned with 
great care, removing from them all the super- 
fluous’ membranes, and other matter that 
could possibly be scraped off ; but notwith- 
standing all those precautions, he found the 
largest and lightest of those prepared blad- 
ders to be somewhat too heavy for the pur- 
pose. Some' swimming-bladders of fishes 
were also found too heavy lor the experi- 
ment ; nor could he even succeed to make 
any durable light balls by blowing hydrogen 
gas into a thick solution of gums, thick var- 
nishes, and oil paint. In short, soap-balls, 
inflated with hydrogen gas, were the only 
things of this sort which lie could elevate in 
air ; and these perhaps were the lirst air 
balloons that were ever constructed. 
Not long after this, news was received from 
France of the success which had attended air 
experiment of a similar nature made at Avig- 
non, by Stephen Montgolfier ; but the bag 
was not filled with hydrogen gas. It was 
filled with air rarefied by heat, which of 
course was lighter than an equal bulk of com- 
mon air of the usual temperature. 
It is said that the two brothers, Stephen 
and John Montgolfier, began to think on the 
experiment of the aerostatic machine as early 
as the middle or latter end of the year 1782. 
The natural ascension of smoke, and of tine 
clouds in the atmosphere, suggested the first 
idea ; and to imitate those bodies, or to en- 
; close a cloud in a bag, so that the latter 
might be elevated by the buoyancy of the 
former, was the lirst project of those cele- 
brated gentlemen. 
Stephen Montgolfier, the eldest of the two 
brothers, made the first aerostatic experiment 
at Avignon, towards the middle of Novem- 
ber, 1782. The machine consisted of a bag 
of fine silk, in the shape of a parallelopipe- 
don, open on one side, the capacity of which 
was equal to about 40 cubic feet. Burning 
paper, applied to its aperture, served to rare- 
fy the air, or to form the cloud; and, when 
sufficiently expanded, the machine ascended 
rapidly to the cei ing of the room. Thus the 
original discovery was made, which was af- 
terwards confirmed, improved, and diversified, 
by different persons in different parts of the 
world. 
As soon as the news of Mr. Montgolfier’s 
successful experiment reached Paris, the 
