the Elements Carbon, Boron, and Silicon. 283 



mental methods were not delicate enough to determine this 

 question with precision, it is safer to deduce from the foregoing 

 results the following generalization only — that, from a red heat 

 upwards, the specific heat of carbon does not vary more than the 

 specific heats of those elements which fulfil the law a/" Dillon g and 

 Petit. Thus Bede*^ shows that the specific heats of the follow- 

 ing elements for the temperatures T are 



Copper =0*0910 + 0-000046T, 

 Zinc . =0-0865 + 0-000088T, 

 Lead . = 0-0286 + 0-000038T. 



(2) The specific heats of graphite and diamond are identical 

 from the temperature 600° and upwards (there are slight diver- 

 gencies, but they do not exceed ^ to 2 per cent, of the value of 

 y) . By reducing, by the help of the mean differential quotient 



Ay 



^T7F = '0000656, the above values for the specific heat of gra- 

 phite to the temperatures 606 o, 7, 806°-5, and 985°'0, and com- 

 paring these with the specific heat of diamond at the same tem- 

 peratures, we obtain the numbers 



Graphite. 

 ^=0-4431 



Diamond. 

 0-4408 



Difference. 

 00023, 



2/ 8 .e. 5 =0-4529 



0-4489 



0-0040, 



y 985 . =0-4674 



0-4589 



0-0085. 



Although the small difference increases with] an increasing 

 temperature, nevertheless it is not greater than the difference 

 between the specific heats of different modifications of other ele- 

 ments. Thus, according to Regnault, the mean specific heats 

 between 10° and 100° for steel and copper are 



Soft steel =0-1165 

 Hard steel =0-1175 



Soft copper =0-0948 

 Hard copper = 0-0934 



These differences may be accounted for by the varying mole- 

 cular aggregation of the substances ; and it may be accepted as 

 true that from a red heat and upwards there is no real difference 

 between the specific heat of the graphitic and that of the diamond 

 modification of carbon. Inasmuch* as this result appears to me 

 one of great importance, both as regards the specific heat of the 

 elements in general and that of the modifications of carbon in 

 particular, I have sought to answer the question as to the differ- 

 ence or identity of the specific heats of graphite and diamond in 

 another and somewhat simpler manner. 



On the supposition that the specific heats of graphite and dia- 



. Cour. de VAcad. de Brux. vol. xxvii. ' 

 U2 



