68 



CALORIFIC POWER OF FUELS. 



Gross difference of temperature, A 1.28 



Correction as usual, a o 015 



Difference, A -J- a 1.295 



Calories. Calories. 



Quantity of heat observed, 1.295 1.295X2.681= 3.47189 



Heat of HNO 3 formation 0.06 X 0.23 =0.0138 



Heat of iron-wire combustion 0.025X1.6 =0.04 



0.0538 



Heat of combustion of 606 cc. at o and 760 mm 3.41809 



or per cubic metre at 760 mm. 5640, or 633.6 B. T. U. per cubic foot. 



COMBUSTION USING AN AUXILIARY SUBSTANCE. 



Sometimes an unconsumed residue is left while determin- 

 ing the heat of combustion of some difficultly burning sub- 

 stances, diamond or graphite for instance. In this case a 

 combustible auxiliary is used to obtain complete burning of 

 the sample. The most convenient to use is naphthalin (C, H 8 ), 

 the heat of combustion of which is exactly known, 9692 cal- 

 ories. 



Take petroleum coke, which is nearly allied to graphite. 

 It is mixed with a little naphthalin which has been previously 

 melted at a low heat and then cooled. After cooling the 

 weight of the naphthalin is taken. 

 The coke analyzed as follows: 



Carbon. 97-855 per cent. 



Hydrogen 0.489 ' ' " 



Oxygen 1.196 " " 



Nitrogen 0.260 " " 



Ash.. 0.200 " " 



100.000 



