﻿PROXIMATE ANALYSIS OP COALS. 47 



Negros coal was analyzed by our transition method and the routine 

 results obtained were as follows : 



Per cent. 

 Moisture 18.95 (18.95) 



Volatile combustible matter 32.39 32.66 



Fixed carbon 31.07 



Ash 17.59 



100.00 



After making due allowance for the variation in the moisture content, 

 these analyses are almost identical with those given above, obtained by the 

 same method. Furthermore, portions of this sample were given to 

 Mr. P. J. Pox (1) and Mr. L. A. Salinger (2) of this Bureau with 

 directions to determine the volatile combustible matter by the official 

 method and also by the smoking-off process. 



A 30 cubic centimeter platinum crucible was used in making these 

 determinations in ( 1 ) . The variation between a crucible of 20 and one 

 of 30 cubic centimeters hardly affect the process noticeably, except where 

 a mechanical loss is involved. 



The results are as follows : 



By the official method : 9 







Per cent. 







(1) 



(1) 



(i) 



Moisture 



(18.24) 



(18.24) 



(18.24) 



Volatile combustible matter 



34.67 



36.49 



33.44 



As one would anticipate, when a larger crucible is used the mechanical 

 losses are not quite so large as in the foregoing determinations; however, 

 about the same variations in the percentage of volatile combustible 

 matter are observed here as in the analyses given above, namely, 3 per cent. 



he smoking-off process: 





Per cent. 







(l) 



(1) (2) 



(2) 



Moisture 



(18.24) 



(18.24) (18.24) 



(18.24) 



Volatile combustible matter 



32.16 



32.21 32.00 



32.00 



Fixed carbon 



31.45 







Ash 



18.15 







100.00 



Here there is almost exact duplication of the previous results obtained 

 by this method. 



For the third sample, Negros coal, No. 23 was chosen, one very high 

 in ash and the one in which the official and smoking-off methods showed 

 the greatest discrepancies in the percentage of ash. 



9 The average of my own duplicated water determinations has been used. In 

 a single determination Mr. Fox obtained 18.37 *per cent. 



