Determination of Energy Dissipated in Condensers. 227 



by the mass of water per second gives the rate of absorption 

 and removal of heat. The thermometers are accurately gra- 

 duated and read to hundredths of a degree. The gain in 

 temperature is several degrees, and may be ten or twenty 

 degrees by increasing the quantity of heat generated or 

 reducing the rate of flow of water. Hence the accuracy of 

 the determination of the quantity of heat absorbed is sufficient 

 for most purposes. The chief error is ordinarily due to 

 changes in the temperature of the apparatus itself and its 

 contents. By running the experiment several hours, however, 

 and keeping it as nearly as possible at a constant temperature, 

 this uncertainty is greatly reduced and the error made 

 negligibly small. 



The water flows into the calorimeter from a reservoir about 

 a metre above, this height furnishing the necessary pressure. 

 The temperature of the entering water is regulated by adding 

 warm or cold water to the reservoir, and the rate of flow of 

 the water is regulated by an adjustable valve. The water is 

 collected in a litre flask, the time of each litre being recorded. 



3. Test of the Calorimeter. 



Table I. shows the result of one of the tests made upon the 

 calorimeter. A current of electricity passed through a coil 

 of wire within the chamber A, the electromotive force being- 

 measured by a carefully calibrated Weston voltmeter, and 

 the current by a Kelvin balance. The experiment continued 

 for a little more than four hours, while nine litres of water 

 passed through the calorimeter. The rate of absorption of 

 heat was nearly, but not quite, constant, the temperature as 

 indicated by A! having varied slightly. The final tempe- 

 rature was practically the same as that at the beginning, being 

 slightly higher if anything. The average for the nine litres 

 is 12*37 watts absorbed and carried away by the water, while 

 the electrical measurements give 12*34 watts. By continuing 

 the experiment longer and introducing greater refinements in 

 the measurement of the current and electromotive force, a 

 greater degree of accuracy could undoubtedly be attained. 

 But this and other tests showed clearly that for our present 

 purposes the calorimeter was abundantly accurate, and we 

 proceeded to put some condensers into it and measure the heat 

 evolved. 



