GAS. 
inflammable air, or carburetted liydrogen. 
He considered this as a strong argument 
against the modern theory of the formation 
of water ; as, from the dryness of the in- 
gredients, which were previously exposed 
to a red heat, and mixed and experimented 
upon immediately, and the quantity evolved, 
it could not be accounted for upon the sup- 
position of the decomposition of water. 
This objection was successfully combated 
by Mr. Cruickshank showing that the air 
did not contain hydrogen, but was an oxide 
of carbon. It is equally procured from the 
oxides of other metals, and charcoal ; but in 
proportion to the facility with which these 
give up their oxygen, the carbon is more or 
less saturated with it ; so that the product 
is a mixture of carbonic acid gas, and car- 
bonic oxide, tiie proportion of the former 
decreasing as the process is continued. 
The carbonic oxide gas, freed from carbo- 
nic acid by washing with lime- water, is very 
little lighter than atmospheric air. It does 
not explode, when fired in atmospheric air, 
but burns with a blue lambent flame: with 
oxygen gas it detonates. It is noxious to 
animals. Water absorbs about a fifth only 
of its bulk. It is not absorbed by the pure 
alkalies, and does not precipitate lime-water. 
If it be mixed with hydrogen gas, and passed 
through an ignited glass tube, its oxygen 
unites witli the hydrogen to form water, and 
charcoal is deposited. De Saussure, jun. 
however ascribes this appearance of carbo- 
naceous matter lining the tube, to the action 
of the hydrogen on the lead in the glass, as 
he produced it by hydrogen alone with a 
glass tube ; and could not by hydrogen and 
carbonic oxide, in a tube of porcelain. The 
purest oxide of carbon is obtained, by pas- 
sing the carbonic acid gas through red hot 
charcoal. 
Gas, hydrogen. This is generally obtained 
from the reverse of the process for the de- 
composition of water. Iron moistened with 
water becomes oxided, by decomposing the 
water ; hut this process is very slow. If 
the vapour of water be passed through a 
tube containing iron wire kept at a red 
heat, the decomposition will go on with 
much more celerity. But the readiest 
method is to employ an acid, as the sulphu- 
ric, diluted with five or six times its weight 
of water, poured on iron filings or turnings, 
or on zinc in small pieces. Zinc affords it 
the purest, as that from iron is apt to be 
contaminated with carbon. Muriatic acid 
diluted with twice or thrice its weight of 
water, may be employed, but it is less (eco- 
nomical. 
Hydrogen gas is the lightest of all ponder- 
able substances, particularly, if received 
over quicksilver, and freed from any humi- 
dity which it may contain by exposure to 
any substance that attracts water strongly. 
When perfectly dry it is free from smell, but 
when it contains moisture it is slightly foe- 
tid. Though highly inflammable, it extin- 
guishes burning bodies if completely enve- 
loped in it without the contact of oxygen. 
It is incapable of supporting life, but does 
not appear to possess any directly noxious 
quality, as it may be breathed for several 
respirations, or even nearly a minute. Fired, 
in combination with oxygen, it explodes 
very loudly ; but if kindled as it escapes 
from the extremity of a capillary tube into 
the atmosphere, it burns calmly, with a 
white flame, the colour of which, however, 
may be varied by different substances dis- 
solved in the gas. It is thus the philoso- 
phical fireworks without smoke or smell are 
formed. If a tube of glass, metal, or any 
elastic material be held over a jet of in- 
flamed hydrogen gas, musical tones will be 
produced, varying in depth and strength, 
according to the length, diameter, and ma- 
terial of the tube. A glass jar has a similar 
effect, but it must not be too wide, or so 
narrow as to extinguish the flame. Dr. 
Higgins first discovered this property. 
A very high temperature is generally 
considered as necessary to produce the 
combination of hydrogen and oxygen. Biot 
compressed the two gases together in the 
syringe of an air-gun ; they took fire, ex- 
ploded violently, and burst the syringe ; 
but here the temperature was sufficiently 
increased by the pressure. A gentleman 
of Orkney, however, introduced nearly 
equal quantities of the two gases into a 
glass jar over mercury, which stood in a 
room without fire, and with little light, 
from the beginning of January to the end 
of May, when he found, that of twelve 
cubic inches, three and a half had disap- 
peared. The residuum was still a mixture 
of the two gases. 
The chief practical application of hydro- 
gen gas is for the filling air-balloons. 
Gas, hydrogen arseniated. Scheele, dis- 
solving tin in arsenic acid, observed the 
extrication of an inflammable gas, holding 
arsenic in solution. Proust afterwards ob- 
tained it by digesting arsenious acid and 
zinc in diluted sulphuric acid. It may be 
