OXIDATION AND DETERIORATION OF COAL. 207 
carbon dioxide was equal to that of the absorption of oxygen 
while the latter was still very energetic. The evolution of car- 
bon dioxide depends directly on the previous absorption of oxy- 
gen, and therefore the fact that the evolution of carbon dioxide 
by samples EH and #' was more rapid than that in any of the 
others clearly substantiates the assumption as to their previous 
partial saturation. 
The rate of the absorption of oxygen by a given coal varies 
with its previous exposure to the air. Under the same condi- 
tions, it depends upon the size of the grains; it is more rapid 
in the finer particles, probably approximately proportional to 
the surface exposed. The absorption of oxygen, not including 
that replaced by evolved carbon dioxide, was determined in 
two samples each of portions A and C in an apparatus identical 
with that shown in fig. 1 and described above, except that flasks 
of dimensions as indicated were substituted for the 100-cubic- 
centimeter glass pipette f. 
In the larger samples the absorption was so much more rapid 
that the pressure at which the oxygen was supplied became 
diminished and the rate of absorption correspondingly reduced. 
The particles in the samples of the portions were so fine that 
they packed closely, and particularly in the larger samples the 
oxygen could not possibly penetrate uniformly to all parts. The 
relative rate of the absorption of oxygen in the two samples of 
portions A and of C was never equal to the ratio of their weights. 
The above experiments also show that the absorption of oxygen 
is much more rapid during the first few weeks than during the 
subsequent periods. These points are indicated more clearly 
when the results of Table IX are represented graphically as 
shown in fig. 2 in which— 
Curve I =—Portion A (40 grams in 4.390-liter flask) ; 
Curve II —Portion A (100 grams in 4.245-liter flask) ; 
Curve I1J—Portion C (20 grams in 1.394-liter flask) ; and 
Curve 1V—Portion C (40 grams in 1.546-liter flask). 
If coal is stored in air, after a time, the compounds in the coal 
unsaturated with respect to oxygen become saturated and the 
avidity of the whole for oxygen becomes much less as shown 
in Tables VIII and IX. It follows from this that there is much 
more danger from fire during the early stages of storage, and, 
because of this fact, when coal has once been stored as a reserve 
and no serious heating has resulted, it should be left undisturbed 
and the coal for present consumption taken from the newest 
piles. 
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