164 CALORIFIC POWER OF FUELS. 



If the heat of combustion of the coal is 7000 calories, then 

 the loss is 



' =3.92 per cent. 

 7000 



The loss due to these causes in an average coal (4-5 per 

 cent hydrogen and I to 2 per cent moisture) is usually from 2 

 to 4 per cent. 



3. CALORIES OF THE COMBUSTIBLE GASES. 



Carbonic oxide is always present in variable quantities, 

 often hydrocarbons and sometimes hydrogen. This refers to 

 ordinary fuel and the usual methods of burning. The quan- 

 tity of unburnt gases depends on the kind of fireplace used 

 and the system of charging. Thick charges of fuel always 

 increase the volume of unburnt gases; the smallest amount 

 being obtained from small, equivalent charges, fed frequently 

 and using 30 to 50 per cent more air than the theoretical 

 quantity. 



To determine this loss we may commence with the volume 

 or the weight corresponding to I kilogram of coal burnt. 

 The calculation is given on pages 137 and 138. No account 

 need be made of the temperature, the calculation of loss due 

 this having been made on page 161 for all gases, and there- 

 fore for these gases. 



The calorific coefficients of the unburnt gases, referred to 

 a cubic metre at o and 760 mm. pressure, are 



Heat of Combustion. 

 Weight per cub. m. 



in Kilograms. Per Kilo. Per Cubic Metre. 



Hydrogen 0.089 345 3O9 1 



Carbonic oxide 1.251 2435 343 



Methane (CH 4 ) 0.715 13343 10038 



Carbon vapor 1.073 11328 12143 





