66 



CALORIFIC POWER OF FUELS. 



So that the system had lost, before reaching the maximum 

 temperature, 



0.024 + 0.0015 0.0255, 



which must be added to the 3.59 already found, making the 

 variation in temperature 3.615, neglecting the 4th decimal. 

 The quantity of heat observed, then, is 



Q = (2200 + 481)3.615 = 2681 X 3.615 = 9.6918 calories. 

 From this number must be subtracted 



1. The heat of formation of the o. 13 



gram of HNO 3 0.13 X 0.23 = 0.0299 



2. The heat of combustion of 0.025 



gram of iron wire 0.025X1.6 =0.04 



Total subtraction 0.0699 



The final result is, then, 



9.6918 0.0699 = 9.6219 calories, 

 or for I kilogram 962 1.9 calories, equivalent to 17319.4 B.T.U. 



TECHNICAL EXAMINATION OF COAL. 



The coal taken was a sample of Nixon's coal from South 

 Wales. 



