OXIDATION AND DETERIORATION OF COAL. 805 
TABLE VIII.—The comparative avidity of coal particles of different sizes 
for oxygen at 30° C. 
Diminished pressure in millimeters. 
Time after 
starting. 
AA A Cc E F 
0 18 270 109 270 253 165 
0 26 326 147 333 273 224 
0 42 399 191 407 355 295 
8. @ 460 251 472 452 363 
4 0 495 313 505 493 406 
5 0 514 343 520 505 432 
0 | 521 400 | 651 | 516 | 456 
i @ 519 452 523 507 464 
0 
0 
503 544 501 485 447 
477 518 456 462 3886 
It is easily seen from the above table that with each coal the 
pressure diminishes for a time and then increases. The reduc- 
tion in the pressure was due to the gradual absorption of oxy- 
gen by the coal, but in time the rate of the evolution of carbon 
dioxide was equal to that of the absorption of oxygen, and later 
even exceeded it and thereby increased the pressure. These 
observations substantiate the assumptions made in considering 
Tables IV and V, that the evolution of carbon dioxide is sub- 
sequent to the absorption of oxygen. 
The absorption of oxygen by A, the coarsest sample, after 
sealing is not very rapid; but that by C, which is very much 
finer than A, is two and one-half times as fast. Sample AA 
is the same portion as A, but was quickly pulverized in a mortar 
immediately before beginning the experiment, and in this sample 
the absorption in the sealed apparatus was two and one-half 
fold greater than A. On account of the great avidity for oxy- 
gen shown by the finely divided coal, it was anticipated that 
samples # and F which consist of the finest particles, on ac- 
count of the small amounts of these portions obtained in the siz- 
ing, and consequently excessive exposure to the air during prepa- 
ration, might be fairly saturated before the experiment began. 
This was the case as indicated by the low speed of the absorption 
of oxygen after sealing and the comparatively small reduction in 
the pressure before it began to increase. The fact that not so 
great a partial vacuum was produced at any time in these as 
in the fresher samples shows that the rate of the evolution of 
