8 CALORIFIC POWER OF FUELS. 



H = the quantity of hydrogen less that supposed to form 

 water with the oxygen. 



Other authors and experimenters have tried to interpret 

 their results by a general formula with varying success. 

 Many of them by working on a certain number of coals from 

 a certain location work out a formula which applies to that 

 set of coals, but not as well to another set. A few of them 

 will be given. They all resemble Dulong's and are usually 

 only modifications of his original one. 



The Verein Deutscher Ingenieure adopted the following: 



= SiooC + 29000 [H g-J -f- 25008 



in which allowance is made for the heat of combustion of 

 sulphur and the heat of the hygroscopic water. All the 

 coefficients are round numbers and that for hydrogen, 29000, 

 is the one in which the water is supposed to be as aqueous 

 vapor, all the water being considered as passing off in that 

 state. None of the other formulae uses this coefficient. 

 It gives rather low results. The question as to the advis- 

 ability of reckoning the heat due to sulphur is a debatable 

 one. In no case does it amount to more than a very small 

 per cent and can have but little effect on the total. 

 Balling gives as formula 



9 H) 



x = 8o8oC + 34462(11 -- ) - 



to represent the actual occurrences in a steam-boiler fire work- 

 ing under a pressure of steam corresponding to 300 F. 



Schwackhoefer made the following modification to allow 

 for the correction due to hygroscopic water: 



x 8o8oC + 34500 (H -) 637^. 



\ ?S / 



