108 



THE PRODUCTION AND USE OF HEAT 



The principle of the calorimeter is that the heat produced 

 by the body when burned is absorbed by water. As a con- 

 sequence the temperature of the water rises, and by knowing 

 the weight of the water and its rise in temperature the amount 

 of heat which the water absorbed can be calculated. Of 



course every possible means is 

 used to prevent the escape of 

 heat from the water during the 

 determination. 



Figure 83 represents a calo- 

 rimeter used in determining the 

 heat value of fuels. The fuel 

 to be examined is carefully 

 weighed and placed in the 

 metal cup, A; placed inside the 

 metal bomb, B. The bomb is 

 water tight and is placed in the 

 water contained in the vessel, 

 (7. The weight of the bomb 

 and the weight of the vessel, C, 

 are both known. Electric wires, 

 D, carry a current of electricity 

 into the bomb where a wire 

 leads across the surface of the 

 fuel to be burned. The bomb 

 contains oxygen under pressure. 

 The vessel containing the water and bomb is set in a double- 

 walled vessel, E, which prevents the escape of heat from 

 the apparatus. The temperature of the water is taken by 

 means of the thermometer, F. When all is ready, a current 

 of ele'ctricity is passed through the wires. That portion of the 

 wire over the fuel becomes red hot and ignites the charge in 

 the cup. The fuel burns and produces heat which is ab- 

 sorbed by the bomb, the metal vessel, C, and the water. 

 The rise in temperature is determined by means of the ther- 

 mometer. By knowing the heat absorbed by the water and 



FIG. 83. A calorimeter used to de- 

 termine the heat of fuels. 



