46 The Specific Heat of Non-conductors, 



whose specific heat is '46. For calculating the specific heat 

 some fragments of copper were heated and plunged into a 

 known weight of the oil in a small calorimeter, the equation 

 being now as follows 



M(7(T-0) = (Mi^ + ^)(0-^), 

 and 



Mff(T-e) ^ 



where ;ir= specific heat of oil. 



M = mass of copper. 

 M^ = mass of oil. 

 Ic = water equivalent of Calorimeter and stirrer. 

 a = specific heat of the copper. 

 Temperatures denoted as before. 



Example — 65 c.c. oil (sp. gr. = '93) = 6045 grm. Copper = 

 21-63. T-98'o. /= 1845. = 23*10; whence by above 



formula we get 



X = 464. 



The results obtained with vulcanized rubber in the 

 form of sulphured cut sheet, were very similar to the pure 

 rubber. There would be about 5% of sulphur present, of 

 which the specific heat is '202. 



Some preliminary experiments made with gutta percha 

 may also be recorded. This body, however, is difficult 

 to deal with, as it changes its condition when heated, and 

 again when plunged into the calorimeter, taking a very 

 long time to reach the maximum temperature ; gutta percha 

 contains about 30% of two peculiar resins, to which its 

 physical properties are chiefly due. We propose to give 

 some figures concerning this and some allied substances on 

 a future occasion. 



