7 pound carbon.

Air Required for Combustion--It has already been shown that each
combustible element in fuel will unite with a definite amount of oxygen.
With the ultimate analysis of the fuel known, in connection with Table
31, the theoretical amount of air required for combustion may be readily
calculated.

Let the ultimate analysis be as follows:

_Per Cent_
Carbon 74.79
Hydrogen 4.98
Oxygen 6.42
Nitrogen 1.20
Sulphur 3.24
Water 1.55
Ash 7.82
------
100.00

When complete combustion takes place, as already pointed out, the carbon
in the fuel unites with a definite amount of oxygen to form CO_{2}. The
hydrogen, either in a free or combined state, will unite with oxygen to
form water vapor, H_{2}O. Not all of the hydrogen shown in a fuel
analysis, however, is available for the production of heat, as a portion
of it is already united with the oxygen shown by the analysis in the
form of water, H_{2}O. Since the atomic weights of H and O are
respectively 1 and 16, the weight of the combined hydrogen will be 1/8
of the weight of the oxygen, and the hydrogen available for combustion
will be H - 1/8 O. In complete combustion of the sulphur, sulphur
dioxide SO_{2} is formed, which in solution in water forms sulphuric
acid.

Expressed numerically, the theoretical amount of air for the above
analysis is as follows:

0.7479 C x 2-2/3 = 1.9944 O needed
( 0.0642 )
( 0.0498 - -------) H x 8 = 0.3262 O needed
( 8 )
0.0324 S x 1 = 0.0324 O needed
------
Total 2.3530 O needed

One pound of oxygen is contained in 4.32 pounds of air.

The total air needed per pound of coal, therefore, will be 2.353 x 4.32
= 10.165.

The weight of combustible per pound of fuel is .7479 + .0418[27] + .0324
+ .012 = .83 pounds, and the air theoretically required per pound of
combustible is 10.165 / .83 = 12.2 pounds.

The above is equivalent to computing the theoretical amount of air
required per pound of fuel by the formula:

( O)
Weight per pound = 11.52 C + 34.56 (H - -) + 4.32 S (10)
( 8)

where C, H, O and S are proportional parts by weight of carbon,
hydrogen, oxygen and sulphur by ultimate analysis.

In practice it is impossible to o