46 
BULLETIN 102, UNITED STATES NATIONAL MUSEUM. 
COMBUSTION OF NATURAL GAS. 
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The combustible constituents of natural gas are made up of com- 
binations of the elements carbon and hydrogen. When natural gas 
is burned so as to secure perfect combustion, only carbon dioxide 
and water vapor are formed. That is, the carbon of the gas unites 
with the oxygen of the air forming carbon dioxide, and the hydrogen 
of the gas unites with the oxygen of the air forming water vapor. 
The water vapor, of 
course, will condense when 
cooled. This water vapor 
does not come from the 
gas, but is created and 
formed by the chemical 
action of the hydrogen in 
the gas and the oxygen in 
the air. 
Each cubic foot of nat- 
ural gas burned requires 
approximately 9J cubic 
feet of air, forming 10J 
cubic feet of combustion 
products, which are made 
up of 2 cubic feet of 
steam, 1 cubic foot of car- 
bon dioxide, and cubic 
feet of nitrogen, all thor- 
oughly diffused through 
each other. 
The combustion of 1,000 
cubic feet of natural gas 
will form 2,000 cubic feet 
of water vapor or steam, 
and this when condensed 
will make approximately 
10-J gallons of water. This 
is not peculiar to natural 
gas, but is true of all gases containing hydrocarbon compounds. 
One thousand cubic feet of manufactured gas will form about 
one-half the water vapor produced by the combustion of 1,000 
cubic feet of natural gas. It is this water vapor that causes the 
bakers and broilers of stoves to rust, and where gas is used in open 
fires without flues, or for lighting, makes the walls and windows 
sweat and glued furniture open up. 
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FIG. 18. CURVE SHOWING EFFECT OF GAS PRESSURE ON 
GAS VOLUME AND GAS HEATING VALUE. 
