IRON MANUFACTURE. 519 
furnaces, as applying here, this item would be about 300 units. The 
account thus stands: 
NG Ne ar ape eM RM RT RE sci ak laa eR Unie a gabe dude re bond o-caaustioeseceehe 1,692 
1B LacdoceceSdSco AASONOSESEEE IGT HE BEIESe m tiria tt fe 2 Nien i Dn er 907 
(OQ). aie chic ANC ALG Benes ta th se AMHR A Ar ao oR CRA eo ee 650 
11D) PE ARR IN We LRM ean nce di Wine wis Sane REE aE te ol ds olbes kaiaels 300 
GROEN aa adama chon eoiGrcn a DOSeOS CSCS OCC RC COC CCE NC Ren rt nia pee OnE 3,549 
There is one more item, large and unsettled in this case—the heat 
carried off as sensible heat in the gases. Calling this X, we have the 
total heat requirement of the furnaces = 3,549 + X for each ton of 
iron made. 
To calculate X, the temperature of the gas need be known, which 
in the present instance could not be ascertained. ‘The throat of the 
furnace is a bright red, however, and hence this could not be less 
than 600° centigrade. On this assumption a value of X would be ob- 
tained as follows: 
The blast required per ton of iron was before calculated at 
176,000 cubic feet, equal to 6.379 tons. The gas produced would 
equal in weight this amount plus the carbon in the limestone 
and fuel, and the oxygen in the ore and carbonic acid of the 
limestone. The total weight. of gases would then be per ton of iron, 
after adding these items, 8.300 tons. This is large. The amount of the 
gases in the Cleveland blast furnaces (England) is from 6 to 7 tons per 
ton of iron. Taking the mean specific heat of the gases at 0.24, the 
heat required to raise them to 600° centigrade would be 8.300 .24 x 
600 = 1,194 heat units, making the total heat requirement 3,549 + 
TY es 2) Sy 
Of the sources of heat the blast (6.379 tons at a temperature 
of 500° centigrade) would give about 750 units, leaving in round 
numbers 4,000 units to be accounted for from the fuel. This fuel first 
burns at the tuyeres to carbonic oxide, and gives in so doing 2,400 units 
per unit of fuel. We may first assume that all the carbon, except that 
required to decompose the carbonic acid of the limestone, reaches the 
tuyeres ; there would be 1.235 tons then burned; 1.235 < 2,400 gives 
2,964. Again, part of this carbonic oxide is burned in the upper part 
of the furnace by the oxygen of the iron ore into carbonic acid, and 
gives for each unit of oxygen so used 4,200 units of heat, but 0.94 ton 
