878 
purely empirical and depends on the volatile combustible matter of one 
coal having the same calorific value as that of every other coal of the 
same percentage composition, which fact is questionable. The facts 
expressed in Table X of this investigation show that this statement is 
more or less true, and since the error from this source can influence only 
one factor, it is thought that an empirical formula of sufficient accuracy 
may be obtained which will be of some assistance to practical workers. 
The formula as proposed by Goutal is as follows: 
P=81.5 C+aV where, 
P=The heating power in calories. 
‘==Percentage of fixed carbon, as determined by analysis. 
V= Percentage of volatile combustible, as determined by analysis. 
a= An empirical value, varying with the percentage of volatile combustible 
to total combustible matter in the coal—i. e., 
per cent volatile combustible 
100 — (per cent moisture+ per cent ash). 
The values given are as follows: 
When the percentage of volatile ; : 
combustible to total combustible « 
matter is equal to— Then a is equal to— 
5 145 
10 » 130 
15 117 
20 109 
25 103 
30 98 
35 94 
40 85 
The numbers given by Goutal have not been carried far enough to be 
of any assistance in determining the calorific power of Philippine coals. 
I have therefore collected proximate analyses of coals, on which calorific 
determinations have been made, of the same grade as those from this 
Archipelago, from as many sources* as possible and have calculated 
values for a from them. The total number of analyses used in this 
collection was 150, and the results of calculating by means of these 
numbers agreed in nearly every case within 1.5 per cent with those deter- 
mined by experiment. The numbers are as follows: 
4U. 8. G.S., P. PB. 48 (1905), 1; W. Virginia G. 8. (1903), 2; Maryland G. BS. 
(1905), 5; U.S. GS. 22d An. Rep. (1900-1901), 3; U. 8S. G@. 8S. Bull, 218 (1903). 
