CALORIFIC VALUE OF PHILIPPINE COALS. 175 



The literature is full of material showing an agreement within 2 or 3 per 

 cent between results .obtained by direct determination and those calculated from 

 elementary analyses.'* Lord and Haas " have shown from their work that the 

 results on American coals "if calculated from the ultimate analysis, might he 

 expected to lie Arithin two per cent of the calorific value" and the work of the 

 Coal Testing Plant -° at St. Louis has shown a similarily close agreement. 

 However, all of these formulae have the disadvantage that elementary analysis 

 is too tedious for ordinary technical work. At the time these were originally 

 proposed, it was much easier to make an elementary analysis, in point of time 

 at least, than to make a determination of the heating power. To-day it is 

 simpler to determine at once calorimetrically the heating power of the material 

 than to carry out an elementary analysis. 



The prediction of the heating power of a coal from the results of a 

 proximate analysis was suggested by Kent -^ in 1893. 



He writes, "Mahler's results group themselves very closely around the average 

 curve of the diagram, indicating therefore that there is a law of relation between 

 the composition of the coal as determined by proximate analysis and the heating 

 value. Knowing, therefore, the percentage of fixed carbon in the dry coal free 

 from ash, we may in the case of all coals containing over 58 per cent of fixed 

 carbon, predict their heating value within a limit of error of about 3 per cent." 



A formula for the derivation of the calorific power from the proximate 

 analysis was first proposed by Goutal ^- in 1896. Later De Paepe "^ 

 applied it to a wider range of coals and suggested some modifications 

 for the values first proposed. Since then Goutal has extended his 

 investigations to more than six hundred anthracitic and bituminous 

 coals and finds ^* that the calorific value can be calculated with sufficient 

 accuracy for industrial purposes. 



Such a fornrala is only an approximation. It would be impossible 

 to derive an absolutely correct formula from analyses made by an entirely 

 empirical method, bf a substance so complex and varied as coal. How- 

 ever, it has often been recorded ^° that the results obtained by calculation 



" Alix, J., and Bay, I. Compt. rend. Acad. sci. (1904), 139, 215 have pointed 

 out that nearly all coals contain more or less calcium carbonate, and in the 

 ultimate analysis the carbon dioxide from this is also calculated to carbon. This 

 may be a source of variation. 



" Trans. Am. Inst. Min. Eng. ( 1897 ) , 1 7, 268. 



'-°Prof. Papers 48, U. 8. Geol. Surv. (1906), 1, 174. 



"Kent, W. Mineral hid. (1892), 1, 105. 



-Ann. ohim. anal. (1896), 1, 169; Rev. d. chim. ind., (1896), 7, 65. 



='De Paepe, D. Bull. Ass. lelge (1898), 12, 279. 



"Goutal. Compt. rend. Acad. sci. (1902), 135, 477; Ann. chim. anal. (1903), 

 8, 279; Analyst (1903), 28, 128. 



=" Noyes, W. A., McTaggart, J. R., and Graver, H. W. Journ. Am. Chem. 8oo. 

 (1895), 17, 843; Gill, A. H. Gas and Fuel Analyses for Engineers, N. Y. (1902), 

 90; Hempel, W. Ztschr. f. angew. Chem. (1892), 5, 389. 



