﻿TROXIMATE ANALYSIS OF COALS. 65 



SUMMARY. 



(1) The directions for coal analyses recommended by the committee 

 appointed by the American Chemical Society are inapplicable to certain 

 Philippine coals. 



(2) These coals are easily detected by the shower of incandescent 

 carbon particles which are driven off when the sample is subjected to 

 rapid heating. 



(3) This mechanical loss can be overcome by expelling the volatile 

 matter with sufficient slowness so that the escaping gases do not ignite. 

 This is demonstrated by the fact that when the fixed carbon is burned 

 to ash, the percentage of the latter is much higher than that obtained 

 by the official method. 



(4) An increase in the amount of moisture in a coal increases the 

 percentage of volatile combustile matter when the official method is 

 used.' When the smoking-off method is applied — that is, when the gases 

 are expelled very slowly — a variation in the amount of water produces 

 no change. 



(5) A comparison of the official and the smoking-off methods shows 

 a difference in the breaking down of the volatile ingredients of a coal. 

 This discrepancy is least in those coals where there is mechanical loss 

 by the former method. It varies with the complexity of the volatile 

 constituents and is probably due to the variation in the heavy hydrocarbon 

 content, for those coals to which the official method is inapplicable are 

 deficient in illuminants. 



(6) If the smoking-off method is employed only when the official 

 method gives inaccurate results, the difference in the breaking down of 

 the volatile constituents is less than that produced by a variation in the 

 amount of water in a coal analyzed by the official method. Under these 

 conditions it will suffice for commercial purposes to neglect the variation 

 in the breaking down of the volatile ingredients by the different heat 

 treatments and to consider the results as directly comparable to those 

 obtained by the official method. 



(7) The official method is assumed to approach the conditions exist- 

 ing in a coke oven. In actual practice the coal is charged in large bulk 

 and the distillation necessarily begins slowly. In the smoking-off method 

 furnace conditions are more nearly attained. 



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