SPECIFIC HEAT OF THE BODY. 



435 



weight (1) of the empty glass, (2) after it is filled with the solid substance, (3) 

 after the fluid is added, so that we obtain the weight of the solid substance, m, 

 and that of the fluid,/. The test-tube and its contents are placed in a mercury 

 bath, BB, and this again in an oil lath, C C, and the whole is raised to a high 

 temperature. Into BB there is introduced a fine thermometer, T. When the 

 tube, A, has reached the necessary temperature (say 40) it is rapidly placed in 

 the water of the accompanying calorimeter-box, D D. The water in this box, 

 which also contains a thermometer, D, is kept in motion until it has completely 



BB 



Fig. 169. 

 Kopp's apparatus for the estimation of specific heat. 



absorbed all the heat given off by A. Let T represent the temperature to which 

 A and its contents were raised in the mercury bath, and Tj the temperature to 

 which it fell in the calorimeter; let s be the specific heat, and m the weight of the 

 solid substance in the test-tube, while a and /u represent the specific heat of the 

 weight of the interstitial fluid in the test-tube; and lastly, let w equal the amount 

 of water in contact with A, which absorbs and gives off heat; then W represents 

 the amount of heat which the test-tube and its contents give off during cooling. 



W = (*. m + w + <r. M ) (T - T!). 



The amount of heat, Wi, absorbed by the calorimeter is 



W 1= M (<!-0, 



where M represents the amount of water in the calorimeter, and t the original 

 temperature of the water in the calorimeter, and t l the temperature to which it is 

 raised by placing A in it. If W and Wj are equal, then 



Tke specific heat, s = M (*, -0 - 



(T - TI ) 



m 



If a fluid substance is placed in the test-tube, and its weight = m, and its 

 specific heat = s, the formula for the specific heat of the fluid to be investigated is 



M 



s = 



-<)-w (T-T,) 



m(T-Tj). 



This is a subject which has been very slightly cultivated. J. Rosenthal in his 

 investigations used an ice-calorimeter ( 206). 



