IO CALORIfIC POWER OF FUELS. 



Three elements enter into these cases, the analysis, the 

 calculation, and the combustion; all may be erroneous. As 

 the matter stands now the weight of error seems to be on the 

 side of the analysis, as our methods of analysis, especially in 

 water determinations, are not entirely satisfactory; yet it must 

 be confessed that some of the most recent analyses give a 

 basis trom which very close agreement can be calculated. 

 With such fuels as coke, charcoal, or anthracite, having but 

 little volatile matter, the results agree quite well, but with the 

 bituminous coals, asphalts, mineral oils, etc., which are so 

 very complex, the differences are greater.* In these the 

 actual proximate chemical constitution seems to make a differ- 

 ence. It may be safely stated, however, that for ordinary 

 industrial uses, in absence of the possibility of a calorimetric 

 test, and with coals having under 20 per cent of volatile 

 matter, a fairly accurate approximation may be arrived at by 

 calculation. 



The great inducement that formerly existed in favor of 

 calculated results exists no longer. I refer to the difficulty 

 of making a calorimetric test. These can be made now by 

 means of the modern apparatus, so simple and almost self- 

 regulating that the time consumed is but a small fraction of 

 that needed for an analysis, and the labor and care, hardly 

 anything in comparison. 



If possible, by all means have a calorimetric test. If not 

 possible, use the best analysis available. 



CALCULATION FROM QUANTITY OF OXYGEN USED. 



This is the litharge reduction test. It depends on 

 Welter's formula, which is based on the hypothesis that the 

 heat of combustion is proportional to the quantity of oxygen 

 consumed: 



N= mP, 



* Mahler's limit for Dulong's formula is O -f N > 15. 



