ON THE GASES EVOLVED FROM IRON FURNACES, 177 
proportion as in air, and would not have become richer in oxygen gas. But 
it will be seen that this is really not the case by the following table of the 
varying proportions of oxygen and nitrogen in the gases collected from the 
various depths :— 
79:2 
23:7 
79:2 
28:2 
79-2 
24:6 
79°2 
19°5 
79°2 
25°7 
79:2 
24:9 
Nitrogen............ 79:2 
23°6 
Oxygen ....+...+... 27-7 | 27:8 
79-2 | 
We see from this series of numbers, that the relation of the gases, as re- 
gards their proportions from the mouth of the furnace downwards, is quite 
the reverse of that observed in the German furnaces. At first sight the cir- 
cumstance strikes us as very inexplicable, because we do not know any che- 
mical process in the furnace capable of diminishing the amount of oxygen 
contained in the gases; but we are enabled to explain this anomaly on an 
attentive consideration. The diminution of oxygen begins chiefly at the 
point where the gases generated by the combustion of coal become developed. 
The proportion of these gases to each other, shows that, when liberated from 
the coal, they cannot mix quite uniformly with the column of air ascending 
from the lower parts of the furnace. Hence the gas collected at this region 
of the furnace is richer in the gaseous products of distillation of coal than 
would correspond to its average composition; the hydrogen, for example, 
actually increases to above 12 per cent. If we suppose, as we have done in 
the above numerical series, that the hydrogen is derived from the decompo- 
sition of water at the expense of the carbon, the quantity of oxygen could 
not decrease, whatever may be the proportion of the gases generated in this 
way at the various points of the furnace. But if, as we must suppose, the 
hydrogen is principally derived from the olefiant gas and empyreumatic oils 
decomposed by the high temperature, the calculation leads us to a smaller 
quantity of oxygen than really represents the truth. This fact warrants the 
conclusion,—That the mean composition of the gases cannot be determined 
at that point of the furnace where the evolution of gas by distillation is at its 
maximum. 
The source of this uncertainty disappears in the deeper parts of the furnace, 
where the olefiant gas and the higher hydrocarbons are no longer present. 
The result obtained at the depth of twenty-three and twenty-four feet, giving the 
constant mean proportion 79°2: 27, proves that under thetwenty-four feet, there 
is an evolution of carbonic acid caused either by the reduction of the ore, or by 
the escape of carbonic acid from the limestone, or perhaps by both causes 
together. Now we conclude, from the average composition of the gases 
evolved from the materials used in the furnace, that this evolution of car- 
bonic acid is really owing to the reduction of the ore, and that the process 
of reduction takes place only in the boshes. The average composition must 
be somewhere between the following numbers :—— 
NMatrogen j.0ii0y Mak) sree) eye GO90T.».-»-. 57878 
Carbonic acid ...)+- - . 8370 .... 9823 
Carbonic oxide. . . - 26°846 .... 24042 
Light carburetted hydrogen wig: RIA a Sa ain once 
iydresenisi si exisgges nie LILZG,..., 0) 4 OC2 
Olefiant gash) wid singe) DLL, «5,05 0392 
Sulphuric hydrogen . . . 0045 .... 0:035 
Ammonia. ..... + 45 «+ » 0058 ..... O115 
a 100-000 100-000 
