ON LIQUID FUEL. 
10.3 
In the combustion of carbon, under the conditions above mentioned, the products con¬ 
stituting the furnace gas amount to nearly 25 pounds per pound of carbon burnt, and 
they require the following quantities of heat to raise their temperature one degree of 
Fahrenheit’s scale:— 
Pounds. 
Specific Heat. 
Heat units. 
Heat units. 
Carbonic acid gas 
. . . 3-67 
X 
•217 =Z 
•79639 
Nitrogen. 
. . . 894 
X 
•245 — 
2-19030 
Surplus air . 
. . . 11-61 
X 
•238 = 
2-76318 
24-22 
5-74987 
The increase of temperature resulting from the combustion of carbon is therefore 
found by dividing the number of heat units, representing the total quantity of heat ge¬ 
nerated, by the number of heat units requisite to raise the temperature of these combus¬ 
tion products, etc., one degree, and it amounts to 
2522° F. 
14,500 
5-75 
In the combustion of hydrogen under the same conditions, the products constituting 
the furnace gas amount to about 70 pounds per pound of hydrogen burnt, and they re¬ 
quire the following quantities of heat to raise their temperature one degree of Fahren¬ 
heit’s scale:— 
Water vapour . 
Nitrogen gas . 
Surplus air . . 
Pounds. 
Specific Heat. 
Heat units. 
Heat units. 
9 
X -475 = 
4-27500 
26-78 
X ’245 = 
6-56110 
34-78 
X *238 = 
8-27764 
70-76 
19-11374 
Consequently, the increase of temperature resulting from the combustion of hydrogen 
is:— 
2791° F. = 
G2.032 — 8G95 
19-114 
So far, therefore, as relates to increase of temperature, the effect produced by the 
combustion of hydrogen under these conditions is not much greater than that produced 
by the combustion of an equal weight of carbon, notwithstanding the great difference 
in the actual quantities of heat generated, as shown below:— 
Total heat 
generated. 
Available 
heat. 
Increase of 
temperature. 
' Carbon. 
Hydrogen. 
Pound. 
I 
1 
Heat units. 
14,500 
62,032 
Heat units. 
14,500 
53,337 
2522° F. 
2791° F. 
We have now to consider what portion of the available heat is, under ordinary condi¬ 
tions, effective in producing steam. The heated furnace gas, resulting from the com¬ 
bustion of the carbon or the hydrogen of fuel, is the medium by which the heat generated 
is transferred to the water in the boiler; and if it could be managed that, between the 
moment of combustion and the time when the furnace gas resulting from it is discharged 
into the chimney, the whole of the available heat could be communicated to the water 
in the boiler, the evaporative effect realized might then be equal, or nearly equal, to the 
theoretical evaporative power of the fuel burnt. But this is never the case in ordinary 
practice. 
