CALORIFIC VALUE OF PHILIPPINE COALS. 199 



often have originated from a misconception of the moisture in coal. 

 Moisture as ordinarily determined is indeed variable, but is of great 

 importance. The coal-testing plant of the United States Geological 

 Survejf "" have advanced in the right direction in reporting their results 

 in two ways, first, upon the sample as received and secondly, upon the 

 air-dried coal. Almost every coal seam has an amount of water which 

 is characteristic of the coal itself and this has an important significance 

 in the estimation of the value of the fuel; this is indicated by the 

 amount of moisture in the air-dried coal. The difference between this 

 value and the sample as received at the laboratory gives the amount 

 of water which is variable with the exposure of the coal, the season 

 of the year, the state of the weather, the temperature, etc., or perhaps 

 the wetting it has received at the hands of an unscrupulous dealer. 

 In 1866, Eeder "^ carried on some interesting experiments with regard 

 to the variation in weight of coal and coke produced by rain, when 

 they are transported in open railway cars. He found that they increased 

 in weight under the conditions of his experiments from 4.6 to 9.6 

 per cent after from one to five days' exposure. If the plan of the 

 cohl-testing plant "^ is followed consistently, the confusion with regard 

 to the moisture in coal will disappear and the interpretation of the 

 results be simplified. However, usually the purchaser wishes to know 

 how much water is in the ton of coal which he buys, regardless of how 

 it came there. It is the same inert body with respect to the fuel value 

 of the coal in any event, and the heating jjower of the sample is lowered 

 approximately in proportion to the quantity of this present, as well 

 as by the percentage of ash. The calculation of the results to the basis 

 of dry coal is very simple, if that is a more satisfactory basis for 

 specification. 



Even from a practical standpoint it is of great importance to know 

 the amount of volatile and flsed combustible matter in coals. This 

 plan for the analysis of coal was originally formulated when the bulk 

 of the coal used was coking and it was desirable to know the amount 

 of coke that could be produced from a given coal. However, this is 

 a natural distinction and is very useful for noncoking coals, for the 

 two kinds of combustible matter differ in heating j)Ower. The calorific 

 value of the fixed carbon is nearly the same for all coals, but that of 

 the volatile combustible matter is very variable for widely different coals. 

 If the specifications in the purchase of coal should be made on a basis 

 of the dry coal, it is still necessary to determine the moisture in order 

 to calculate the amount of coal received. If it is more intelligible to 



™ Somermeier, E. E. Journ. Am. Chem. Soc. (1906), 28, 1630. 



"'Reder, Ztschr. d. Vereins deutseher Eisenbahnverwaltungen (1866), No. 43; 

 Polytech. CentralU. (1866), N. F. II, 20, 1447; Jahresh. d. chem. tech. (1867), 

 12, 723. 



"' Somermeier, loc. cit. 



