166 REPORT—1845. 
itself during the development of 100 parts of the furnace-gases. The only 
source of heat in the furnace is the oxidation of carbon, and this oxidation is 
effected at the cost of the air introduced by the blast, and that of the oxygen 
contained in the oxide of iron. Let us now consider the influence on the 
units of heat occasioned by the combustion of the carbonic oxide at the ex- 
pense of oxygen in the oxide of iron. From the posthumous results of Du- 
long on the heat of combustion, it follows that the quantities of heat evolved 
by the combustion of 1 lit. (61:028 cubic inches) of oxygen with iron or with 
carbonic oxide is almost quite equal. The first gives 6216 and the latter 
6260 units of heat. The trifling difference between these numbers is quite 
within the limits of error of observation, and therefore we may draw the con- 
clusion, as Ebelmen has already done, that the reduction of the oxide of iron 
is without influence upon the development of heat in the furnace; for in the 
reduction of the oxide of iron at the cost of the carbonic oxide a thermo- 
neutrality takes place. Hence the combustion of the oxygen of the air is the 
only source of heat in the furnace. It suffices to determine the amount of 
oxygen which has accompanied the 59°559 nitrogen into the furnace in the 
form of atmospheric air, in order to fix the amount of heat generated. The 
carbonic oxide formed by the combustion of this oxygen is the only source 
of heat realized in the furnace, and corresponds, as will be seen in the follow- 
ing calculation, to 20001. For every 20001 units of heat realized in the 
furnace, 88374 are lost by the gases which escape. 
Hence follows the remarkable conclusion, that in the furnaces of Al- 
freton not less than 81°54 per cent. of the fuel is lost in the form of combus- 
tible matter still fit for use, and that only 18°46 per cent. of the whole fuel 
is realized in carrying out the processes in the furnace. 
The maximum temperature which might be obtained by the combustion 
of the gases may easily be deduced by the following considerations. 1 kil. 
(15444 grains) of the gas burned with atmospheric air gives 1:9338 kil. pro- 
ducts of combustion, of the following composition and specific heat :— 
Nitrogen: se), yy ets s oy SOBDLG, 0.0 §, O71 889 
Rarbonieacidsaian «<6 3 «A896. oe) 5. OO0RDE 
Aqueous'vapour. ©... - .- 2088 . . O0L76 
100°000 0°2696 
If we divide the units of heat, viz. 883-74, arising from the combustion of 
1 kil. of the gases, by the number resulting when the quantity of the pro- 
ducts of combustion is multiplied by their specifie heat (19338 x 02696), 
we obtain for the temperature of the flame 16952 C., or 3083° Fahr. It is 
obvious that the gases escaping from the furnace must be of still more value 
as fuel than that expressed by our calculations founded upon their compo- 
sition when of minimum value. They must be of a higher value, from the 
circumstance that the reaction of the liquid products of distillation on the 
red-hot coals produces a number of gaseous substances which must necessarily 
increase their value as fuel. The upper layers of coal, limestone and iron, 
being cold, cause a condensation of the water and tar, both of which drop 
back upon the red-hot coals in the inferior layers, and become partly decom- 
posed into hydrogen and carbonic oxide gas ; whilst another part of the tar is 
broken up into hydrogen, light carburetted hydrogen and charcoal. The 
portions escaping this decomposition are condensed anew by the cold layers 
above, and finally themselves suffer change. For the purpose of determining 
the influence exerted by this circumstance on the composition of the gases, we 
have repeated the experiment on the distillation of the coal, reversing however 
the mode of heating the tube ; we began at the front part instead of the closed 
