HEATING POWER OF COAL. 31 



stated that the heat generated by a fuel during 1 combustion 

 was equal to the sum of the possible heats generated by its 

 component elements, less that portion of the hydrogen which 

 might form water with the oxygen of the fuel. The formulae 

 he gave were : 



X-8080C + 34500 [H (0-8)]. 

 X J =14500C + 62100 [H (O-J-8)]. 



in which X = the heat of combustion sought in calories. 

 X J =the heat of combustion sought in B.T.U. 

 C = percentage of carbon in analysis of the fuel. 

 H = percentage of hydrogen in analysis of the fuel. 

 = percentage of oxygen in analysis of the fuel. 



When hydrogen and oxygen exist in a compound in the 

 proper proportion to form water (i.e., 1 pt. of hydrogen to 8 

 pts. of oxygen), these constituents have no effect on the total 

 heat of combustion. It follows that only the surplus hydro- 

 gen above that required by the oxygen is to be taken into 

 account. 



H (0-r8)=the quantity of hydrogen in the analysis of 

 the fuel less that supposed to form water with the oxygen. 

 In computing the total heat of combustion it is convenient to 

 substitute for the hydrogen the quantity of carbon which 

 would give the same quantity of heat, and this is done by 

 multiplying the weight of hydrogen by 62.0322^-14,500 = 4.28 

 making the formula : 



Xi =14,500 (C + 4.28 [H (0-)]. 



The theoretical evaporative power of lib. of the fuel in Ibs. of 

 water evaporated from 212deg. F. is : 



966, or rather 966.1, is the number of B.T.U. required to 

 evaporate lib. of water at boiling point under a pressure of 

 one atmosphere. This corresponds to 536. T calories, which are 

 necessary to evaporate one kilogramme of water under similar 

 conditions. 



Duloiig's formula does not allow for the heat due to 

 sulphur; this, however, in an ordinary coal is a A*ery small 

 percentage, and will only apply to that sulphur not left in the 

 ash, so it would have very little effect on the toal. If desired 

 to allow for the sulphur, then the formula would read : 



X - 8080C + 34,500 [H (0 i 8)] + 2220S. 

 where S = the available sulphur in the fuel. 



The calorific power computed by formulae from the ulti- 

 mate analysis of a fuel is not quite correct when compared 

 with the results of calorimeters, for errors are apt to creep 

 into the analysis; various authorities differ slightly in tiu'ii 



