GAS. 
fourth of that from stagnant pools, and still 
less of the others. 
Gas, phosphuretted hydrogen. This may 
be procured by boiling in a retort a little 
phosphorus, with a solution of pure potash. 
The phosphorus should be first melted « 
under water in the retort, which is to be 
emptied when the phosphorous has con- 
gealed, and then filled with the alkaline 
solution. Of this a sufficient portion is to 
be displaced by hydrogen gas. Or one 
part of phosphorus, cut into very small 
pieces, and two of finely granulated zinc, 
may be put into ten parts of water, and six 
parts of concentrated sulphuric acid added ; 
the gas is disengaged in small bubbles, 
which cover the whole surface of the fluid, 
and take fire on reaching the air, so as to 
form by their succession a well of fire. 
If two parts of phosphuret of lime, bro- 
ken into pieces the size of a pea, and one 
of hyperoxymuriate of potash be put into an 
ale glass, or a Florence flask ; the vessel be 
filled with water, and six or eight parts of 
concentrated sulphuric acid be poured in 
through a long-necked funnel reaching to 
the bottom ; as soon as decomposition com- 
mences, flashes of fire will dart from the 
surface, and the bottom of the vessel will be 
illumined with a beautiful green light. 
When phosphuretted hydrogen gas is suf- 
fered to escape into the air, as it issues 
from the retort it takes fire, and a dense 
white smoke rises in the form of a horizon- 
tal ring, enlarging its diameter as it ascends. 
It detonates when mixed suddenly with 
oxygen, oxygenized muriatic acid, or ni- 
trous oxide gas. By standing it loses its 
property of spontaneous ascension, the 
phosphorus being deposited on the inner 
surface of the vessel containing it. 
Phosphuretted hydrogen gas may be dis- 
solved in about four times its bulk of distill- 
ed water, at 44° Fahrenheit, and imparts to 
it a bitter taste, and strong unpleasant smell. 
This solution speedily converts the oxides 
of lead and mercury, and nitrate of silver 
into phosphurets of those metals. Nitrates 
of lead, mercury and arsenic, and sulphates 
of copper and iron, are acted upon by it 
more or less slowly ; but some of the phos- 
phurets then formed, are changed by stand- 
ing some time into phosphates. 
The ignis fatuus, or jack with a lantern, 
is supposed to be produced by this gas, 
arising from the putrefaction of animal sub- 
stances in swampy places. 
Gas, sulphuretted hydrogen. This gas, 
formerly termed hepatic air, may be ob- 
tained by adding dilute muriatic acid to a 
solution of sulphuret of potash or of soda, 
which evolves it with violent effervescence ; 
or by pouring diluted sulphuric or muriatic 
acid on sulphuret of iron. Sulphur and iron 
mixed together with a littlejwater likewise 
afford it by distillation. 
Sulphuretted hydrogen is particularly 
characterised by its offensive smell, re- 
sembling that of rotten eggs.. Like the 
other compounds of hydrogen it detonates 
if mixed with oxygen or atmospheric air, 
and then fired, and burns silently if inflamed 
as it comes into contact with them from a 
small aperture. If three parts of it be 
mingled with two of nitrous gas, the mix- 
ture burns with a yellowish green flame. 
This gas is decomposed by oxymuriatic 
acid gas, by sulphurous acid gas, or by be- 
ing kept mixed with atmospheric air, and 
its sulphur is precipitated. If passed through 
ignited charcoal it is converted into carbu- 
retted hydrogen gas. It precipitates all 
metallic solutions, except those of iron, 
nickel, cobalt, manganese, titanium, and 
molybdaena. It tarnishes silver, mercury, 
and other polished metals, and immediately 
blackens white paint. 
This gas is absorbed by water, which at 
55“ takes up .86 of its bulk, and at 85° only 
.78. The solution exposed to the air be- 
comes covered with a pellicle of sulphur ; 
and deposits sulphur even in well corked 
bottles. A few drops of nitric or nitrous 
acid likewise precipitate the sulphur. 
It is remarkable that sulphuretted hydro- 
gen, which contains no oxygen, consisting, 
according to Thenard, of 29 hydrogen, and 
71 sulphur, should possess the properties of 
an acid, reddening litmus paper, and unit- 
ing with the alkalies and all the earths, ex- 
cept alumina and zircon. These compounds 
are soluble, and most of them are suscepti- 
ble of crystallization. They are at first 
colourless, but by exposure to the air be- 
come green, or of a greenish yellow, and de- 
sit sulphur. At length, however, the solu- 
tion again becomes colourless, and the base 
is found ultimately converted into a sul- 
phate. Acids disengage their sulphuretted 
hydrogen gas. Vauquelin, having lixiviated 
a considerable quantity of soda manufac- 
tured in France, found, after some weeks, 
a white transparent salt, crystallized in te- 
trahedral prisms, terminated by quadran- 
gular or octangular pyramids. Its taste 
was jcrid and intolerably bitter, and it had 
a sliglit hepatic smell. It did not precipi- 
tate any of the earthy salts, except those of 
