QUANTITY OF HEAT. SPECIFIC HEAT. . 81 



Alcohol may be used in the inner tube of the Bunsen calorimeter in 

 place of water, for the determination of specific heats below 0. 



The change in specific heat of a number of metals with change of 

 temperature has also been found. Among the most important of these 

 is platinum, on account of its use to determine high temperatures. 

 Violle,* using the method of mixtures, has obtained for this metal over 

 the range to 1200" 



s = -0317 + -000012*. 



Naccari f has found the value for various metals by the method of 

 mixtures, between ordinary temperatures and 320, in the form 



s = a(l+bt) 



The following results are given by him. The unit is the calory at 

 0: 



a 10 6 6 



Copper .... -09205 230'8 



Silver .... '05449 392'9 



Aluminium . . . '21116 449'3 



Lead .... '02973 456'9 



Zinc .... -09070 489-5 



Nickel .... '10427 907-0 



Iron .... -10442 1029'! 



Tilden J has investigated the specific heat of iron, nickel, cobalt, 

 aluminium, silver, gold, and platinum, over the range from 182 C. to 

 + 100 C., extended in some cases to 630 0., and his results show that the 

 specific heat decreases as the temperature of determination decreases. 

 In the case of platinum the decrease is regular, or the relation between 

 specific heat and temperature is linear. But in other cases the decrease 

 is more and more rapid as the temperature falls. 



The most remarkable changes of specific heat are those which occur 

 with carbon, boron, and silicon. These were investigated by H. F. 

 Weber. He used the Bunsen Ice Calorimeter from 50 to + 250, 

 employing alcohol in the inner tube below 0, and for carbon he extended 

 the experiments to the range between 600 and 1000, when he used the 

 method of mixtures. His plan at this higher range consisted in heating 

 a known weight of platinum and the carbon to the same temperature 

 and dropping the two simultaneously, one into each of two water 

 calorimeters. The platinum gave the temperature, while the rise in the 

 other calorimeter, when the temperature was thus known, gave the 

 specific heat sought. His results for diamond between 50 and + 250 

 are nearly represented by 



though the rate of increase is appreciably diminishing as the temperature 



* Phil. Mag., vol. iv., 1877, p. 318. 



t Atti R.A. de Torino, 23, 1889; Beiblatter, xii., 1888, p. 326. 

 J Phil. Trans., A. 194, p. 233, 1900, and A. 201, p. 37, 1903. References to other 

 work will be found in these papers. 

 Pogg. Ann., cliv., pp. 367 and 553. 



F 



