action which takes place is the decomposition of the water vapor, the
hydrogen being liberated, while the oxygen unites with the carbon to
form carbon dioxide:

Carbon. Water.
C + 2H2O = CO2 + 4H2

And the carbon dioxide so produced interacts with more red-hot carbon,
forming the lower oxide--carbon monoxide:

CO2 + C = 2CO

So that the completed reaction may be looked upon as yielding a
mixture of equal volumes of hydrogen and carbon monoxide, both of them
inflammable but non-luminous flames. This decomposition, however, is
rarely completed, and a certain proportion of carbon dioxide is
invariably to be found in the water gas, which, in practice, generally
consists of a mixture of about this composition:

WATER GAS.

Hydrogen 48.31
Carbon monoxide 35.93
Carbon dioxide 4.25
Nitrogen 8.75
Methane 1.05
Sulphureted hydrogen 1.20
Oxygen 0.51
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100.00