54 CALORIFIC POWER OF FUELS. 



With substances containing nitrogen and sulphur, such as 

 coal, the corrections are more complicated, as a larger quantity 

 of nitric acid is formed and the sulphur forms sulphuric acid. 

 If exactness is sought, it will not be sufficient to make a volu- 

 metric test : the sulphuric acid must be determined separately. 

 Generally, however, this estimation may be dispensed with, if 

 for technical purposes only. When, on the contrary, ab- 

 solutely correct figures are desired, both acids must be con- 

 sidered. In the calculation the nitric acid is reckoned as 

 0.227 calorie per gram and the sulphuric acid as 1.44 calories 

 per gram. 



But these two corrections are really unimportant even 

 with coal, as it contains usually only about I per cent of 

 nitrogen or sulphur. One per cent of nitrogen represents 4^- 

 per cent of HNO,, or 10 calories; one per cent of sulphur 

 represents 3 per cent of H a SO 4 , or 43 calories, both quite 

 small compared with 7000 to 8000 calories. 



Below will be found the details of a complete combustion 

 taken from Berthelot's work. 



HEAT OF COMBUSTION OF CARBON. 



The wood charcoal, purified by chlorine at red heat to- 

 remove all traces of hydrogen (Favre and Silbermann's 

 method), is dried at 120 to 140 C. (248 to 284 F.), then 

 weighed in a closed tube after cooling in a sulphuric acid 

 desiccator. 



0.437 gram carbon; cinders, 0.0028 gram (0.66 per cent); 

 real carbon, 0.4342 gram. 



PRELIMINARY PERIOD. 



o minute 17. 360 



1st " 17.360 



2d " 17.360 



3d minute 17.360 



4th " 17.360 



