42 CALORIFIC POWER OF FUELS. 



The gas tested has a value of 5 196 calories per cubic metre. 



Since the calorie is 3.968 times the B. T. U., and the 



cubic metre is 35.316 times the cubic foot, multiplying 



the calories per cubic metre by ^-=10.11235 will give 



B. T. U.'s per cubic foot. 

 Multiplying, then, 



5196 X 0.11235 = 583.8 B. T. U.'s per cubic foot. 



The above example considered the volume of the water. 

 It is sometimes advisable to consider the weight instead. The 

 following example illustrates this : 



Weight of water used during the test 2000 grams. 



Volume of gas burnt 7.23 litres. 



Temperature at inlet 14-4 C. 



" " outlet 36.5 C. 



Then 



2000 X (36.5 - 14-4) 

 Q = = 6102 calories per cubic metre, 



and 



6102 X 0.11235 = 685.6 B. T. U. per cubic foot. 



Two causes of error may occur. It is not certain that the 

 combustion of the gas in the burner is regular; indications by 

 gas-meters are not always very sure, the start being capricious. 

 But these do not have much weight in its use for industrial 

 purposes, for which it is chiefly designed. The results are 

 very near those obtained by other methods. Stohmann, whose 

 competence in such matters is universally recognized, says 

 they give good results. 



Bueb-Dessau, to prove the calorimeter, burnt hydrogen 

 prepared by electrical decomposition, and obtained after cor- 

 rections for thermometer and barometer 34150 calories per 



