102 Onthe Blast Furnace in the Manufacture of Iron. 
duced by the transformation of the same volume of carbonic acid 
into carbonic oxide. The vapor of water alone passed through 
the-ignited coal produces all the effects just mentioned, but the 
absorption of latent caloric is so great as to cause the operation to 
cease ina few minutes. By projecting, however, a mixture of 
air and the vapor of water through the coal, the operation is said 
to be carried on advantageously. 
It was my intention to have remarked at length about the 
effects of the hot blast, but it is now so generally admitted that 
the hot is to be preferred to the cold blast in reducing the iron 
from the ore, and bringing it to its most refined state, that any 
thing on the subject at this time would be superfluous. All that 
is important to make known upon this subject, is the results late- 
ly arrived at by M. Scheerer* as to how it is that hot air produces 
such remarkable effects in the blast furnace. 
‘By calculations based upon his own experiments as well as 
those of others, he was led to the conclusion, that the most ele- 
vated temperature that charcoal ‘could produce in burning in air, 
is 2571° Cent., which is that at which platinum melts. This 
temperature is situated in the middle of the space upon which the 
air is projected, and it goes on diminishing towards the exterior, 
so as to form a space for melting, the center of which is at 2571° 
and the exterior at 1550° Cent. When the hot blast is made use 
of, the temperature of the center does not change, but the por- 
tion heated to 2571° becomes more extended. . The exterior of 
the mass which was at 1550° while using the cold air, acquires 
when the hot blast is employed, a temperature as many degrees 
higher as there is difference between the temperature of the two 
blasts ; for instance, if the temperature of the air be 280° C., that 
of the exterior of the heated mass will be 1830° C.—if 300°.C., 
the latter will be 1850° C, 
Thus the influence that hot air exercises, is to extend the space 
of fusion, which is twice as great with the air at 300° C. as it is 
when the air is at 0° C, 
* Pogg. Ann. lix, p. 508. 
