_Actual Volume_
_for One Pound Carbon_ _Per Cent_
_Cubic Feet_ _by Volume_
Carbon Dioxide 32 = 20.91
Oxygen 0 = 0.00
Nitrogen 121 = 79.09
--- ------
Air required for one pound Carbon 153 = 100.00

For 50 per cent excess air the volume will be as follows:

153 x 1-1/2 = 229.5 cubic feet of air per pound of carbon.

_Actual Volume_
_for One Pound Carbon_ _Per Cent_
_Cubic Feet_ _by Volume_
Carbon Dioxide 32 = 13.91 }
Oxygen 16 = 7.00 } = 20.91 per cent
Nitrogen 181.5 = 79.09
----- ------
229.5 = 100.00

For 100 per cent excess air the volume will be as follows:

153 x 2 = 306 cubic feet of air per pound of carbon.

_Actual Volume_
_for One Pound Carbon_ _Per Cent_
_Cubic Feet_ _by Volume_
Carbon Dioxide 32 = 10.45 }
Oxygen 32 = 10.45 } = 20.91 per cent
Nitrogen 242 = 79.09
--- ------
306 = 100.00

In each case the volume of oxygen which combines with the carbon is
equal to (cubic feet of air x 20.91 per cent)--32 cubic feet.

It will be seen that no matter what the excess of air supplied, the
actual amount of carbon dioxide per pound of carbon remains the same,
while the percentage by volume decreases as the excess of air increases.
The actual volume of oxygen and the percentage by volume increases with
the excess of air, and the percentage of oxygen is, therefore, an
indication of the amount of excess air. In each case the sum of the
percentages of CO_{2} and O is the same, 20.9. Although the volume of
nitrogen increases with the excess of air, its percentage by volume
remains the same as it undergoes no change while combustion takes place;
its percentage for any amount of air excess, therefore, will be the same
after combustion as before, if cooled to the same temperature. It must
be borne in mind that the abov