the Elements Carbon, Boron, and Silicon. 



165 



contains the observed specific heats ; the column AT gives the 

 degrees of temperature between which the experiment has been 

 carried out. 





Regnault. 



De la Rive and 

 Marcet. 



Kopp. 



Wullner and 

 Bettendorf. 



C. 



AT. 



C. 



AT. 



C. 



AT. 



C. 



AT. 



Wood charcoal 



Graphite 



0-2415 

 01977 



02004 



01469 



o o 



18- 98 

 17- 99 

 16-100 



9-98 



0-1650 

 1192 



O 



6-15 

 6-15 



0174 

 185 

 0166 



o o 



21-52 

 22-52 

 22-52 



0-1881 

 01 960 

 01861 

 01429 



O 



24-67 

 24-69 

 23-65 

 24-70 



Gas -coke 



Furnace-coke 



Diamond 





Amorphous horon . . . 



Graphitic boron 



Crystalline boron . . . 



6*2352 

 0-2574 



17-99 

 14-100 







0-254 

 0-230 



18-48 

 21-51 







Amorphous silicon. . . 

 Fused silicon 



0-1750 



01787 



22-100 



21- 99 







0-214 

 0138 

 0165 



21-51 

 21-50 

 21-52 







Crystalline silicon ... 



From these facts I concluded that the specific heats of the 

 different allotropic modifications of these three elements increase 

 in an altogether surprising manner. Inasmuch as the experi- 

 ments upon carbon are the most numerous and the most trust- 

 worthy, the foregoing conclusion can be most confidently applied 

 to this element. To boron and silicon the inference cannot be 

 applied with so much certainty. Kopp's numbers for a tempe- 

 rature ranging from about 20° to 50° are certainly smaller than 

 Regnault's for the interval of temperature 20° to 100°; yet inas- 

 much as Kopp worked with very small quantities and with a not 

 very exact method, it is possible that the differences arose from 

 circumstances other than the mere difference of temperature. 

 The analogous behaviour of carbon and boron towards Dulong 

 and Petit' s law permits us to believe that the great variability 

 in the specific heat of the former element will find its counter- 

 part in a like variation in the specific heat of the latter. 



In an experimental inquiry into the specific heat of the dia- 

 mond*, I showed that the specific heat of this body increases, 

 with increase of temperature, more quickly than that of any other 

 substance ; the values at 0°, 100°, and 200° were almost in the 

 ratios I : 2 : 3. The number expressing the relation of the spe- 

 cific heat of the diamond y t to the temperature t was calculated 

 from the following equation : — 



^=0-0947 + 0-000994/-0-00000036/ 2 . 



* Ber. der deut. chem. Ges. 1872, p. 305 ; and Pogg. Ann. vol. cxlvii. 

 p. 317. 



