GAS. 
Indeed, not only different persons, but the 
same individual, will be variously affected 
by it, perhaps, at different times. Similar 
effects have been produced on those who 
have tried it abroad. 
In debility arising from residence in a 
hot climate, and intense application to 
business, this gas has proved a complete 
remedy. It has given voluntary power 
over palsied parts while inhaled, and the 
subsequent application of other remedies 
has effected a cure. Dr. Pfaff has suggest- 
ed its use in melancholia : but in some 
cases of this disease it has done no good, 
and in one harm. 
Gas, nitrogen or azotic. Under the article 
Atmosphere it has been observed, that 
about three fourths of our atmosphere con- 
sist of gas, unfit to maintain combustion, 
or support life. It is called nitrogen or 
azotic gas, and is a little lighter than at- 
mospheric air. It is incapable of support- 
ing life, or combustion, yet a small portion 
is absorbed in respiration. It is not in- 
flammable, though it unites with oxygen 
in different proportions, forming nitrous 
oxide, when the oxygen is only .37, nitric 
oxide when it is .56, and nitric acid when 
.705. It is one of the most general ele- 
ments of animal substances. With hydro- 
gen it forms ammonia; and Fourcroy sug- 
gested, that it might possibly be the aika- 
ligenating principle, though he confesses 
there are no facts in support of this con- 
jecture ; the name of alkaligen, therefore, 
which has been proposed for it, is certainly 
inadmissible. It dissolves small portions 
of phosphorus, sulphur, and carbon. 
Gas, oxygen. This gas was obtained by 
Dr. Priestley in 1774, from red oxide 
of mercury, exposed to a burning lens, 
who observed its distinguishing properties 
of rendering combustion more vivid and 
eminently supporting life. Scheele ob- 
tained it in different modes in 1775; 
and in the same year Lavoisier, who had 
begun, as he says, to suspect the absorp- 
tion of atmospheric air, or of a portion of 
it, in the calcination of metals, expelled it 
from the red oxide of mercury heated in a 
retort. Priestley called it dephlogisticated 
air ; Scheele, from its peculiar property, 
tire air, a name before given it by Mayow, 
or empyreal air. 
Oxygen gas, forms about a fourth of our 
atmosphere, and its base is very abundant 
in nature. Water contains .85 of it, and 
it exists in most vegetable and animal pro- 
ducts, acids, salts, and oxides. 
This gas may be obtained from nitrate of 
potash, exposed to a red heat in a coated 
glass or earthem retort, or in a gun barrel, 
from a pound of which, about 1200 cubic 
inches may be obtained ; but this is liable, 
particularly toward the end of the process, 
to a mixture of nitrogen. It may also be 
expelled from the red oxide of mercury, 
or that of lead ; and still better from the 
black oxide of manganese, heated red hot 
in a gun barrel, or exposed to a gentler 
heat in a retort with half its weight, or 
somewhat more, of strong sulphuric acid. 
To obtain it of the greatest purity, how- 
ever, the hyperoxymuriate of potash is 
preferable to any other substance, reject- 
ing the portions that first come over as 
being debased with the atmospheric air in 
the retort. Growing vegetables, exposed 
to the solar light, give out oxygen gas, so 
do leaves laid on water in similar situations, 
the green matter that forms in water, and 
some other substances. 
Oxygen gas has neither smell nor taste. 
It is a little heavier than atmospheric air ; 
under great pressure water may be made 
to take up about half its bulk. It is essen- 
tial to the support of life ; an animal will 
live in it a considerable time longer than 
in atmospheric air; but its respiration be- 
comes hurried and laborious before the 
whole is consumed, and it dies ; though a 
fresh animal of the same kind can still sus- 
tain life for a certain time in the residuary 
air. 
Combustion is powerfully supported by 
oxygen gas: any inflammable substance, 
previously kindled, and introduced into it, 
burns rapidly and vividly. If an iron or 
copper wire be introduced into a bottle of 
oxygen gas, with a bit of lighted touch- 
w'ood, or charcoal at the end, it will burn 
with a bright light, and throw out a num- 
ber of sparks. The bottom of the bottle 
should be covered with sand, that these 
sparks may not crack it. Mr. Accum says, 
a thick piece of iron or steel, as a file, if 
made very sharp at the point where it is 
first kindled, will burn in this gas. If the 
wire, coiled up in a spiral like a corkscrew, 
as it usually is in this experiment, be moved 
with a jerk the instant a melted globule is 
about to fall, so as to throw it against the 
side of the glass, it will melt its way 
through in an instant, or if the jerk be less 
violent, lodge itself in the substance of the 
glass. If it be performed in a bell-glass, 
set in a plate filled with water, the globules 
will frequently fuse the vitreous glazing of 
