OXIDATION AND DETERIORATION OF COAL. 309 
The value of the bituminous coal produced in the United States 
during the calendar years 1907 to 1909 was 1,230,836,887 dollars, 
an average annual value of 410,278,962 dollars. If bituminous 
coal suffers an average deterioration of 2 per cent,’ the annual 
loss in the United States from deterioration of coal is over 
8,000,000 dollars, or 4 per cent as great as the total losses of all 
property by fire.’ 
There is also a large loss due to spontaneous combustion of 
coal. Oxidation of combustible matter produces the same amount 
of heat whether the reaction takes place rapidly or very slowly. 
If the heat of a slow reaction can not escape, the same increase 
in temperature will result as when the change takes place rapidly. 
Every combustible substance has its ignition point, and for it 
to burn rapidly it must first be heated to the point of ignition. 
This depends almost entirely on the porosity and the fineness 
of division, together with the chemical composition. If the sub- 
stance is in a large compact unit, its ignition is not easily accom- 
plished, but in a very finely divided state and with sufficient 
oxygen present it may kindle and the combustion be propagated 
with explosive violence. If the amount of coal in a given heap 
be small, there will be no perceptible increase in temperature 
from the heat of the reactions involved, for the heat will all be 
lost through radiation. But if the escape of heat is prevented, as 
is done when fine coal is piled in high heaps, and if a supply of 
oxygen is available, absorption of oxygen with consequent rise 
in temperature will result. The absorption of oxygen by coal 
seems to increase rapidly with the temperature, and eventually 
the kindling point may be reached and visible combustion follow.°® 
°U. S. Geol. Surv. Min. Prod. U. S. Calendar Yrs. 1900-9 (1911), Mar. 
The average annual production of Pennsylvania anthracite is valued at 
157,059,584 dollars. 
™Parr and Hamilton, Econom. Geol. (1907), 2, 703, found that in 20- 
pound lots of Illinois coal “outdoor exposure results in a loss of heating 
value varying from 2 to 10 per cent’’ which substantiates Table IX. Cf. 
also Engineer (London) (1903), Oct. 30, and Bement, A., Chem. Eng. 
(1910), 12, 10. 
*From the data of the National Board of Fire Underwriters, U. 8. 
Dept. Commerce and Labor, Bur. Statistics, Statis. Abs. U. S. (1910), 
586, the estimated fire losses in the United States for the calendar years 
1907 to 1909 aggregate 621,675,709 dollars, an average annual loss of 
207,225,236 dollars. 
* Ordinarily the air furnishes the oxygen for combustion, but it may be 
supplied by other oxidizing agents. In the latter case oxidation may be 
so rapid that it causes an explosion. Certain Philippine coals mixed with 
sodium peroxide at room temperature ignite spontaneously. 
