CARBON 35 



It must be noted that the calorimetric measurements of the 

 heat of combustion of carbon differ considerably with every 

 experimenter. (Favre and Silberman, A. Chim. [3] 35, 357, 1852; 

 Berthelot and Petit, A. Chim. [6] 18, 88-98, 1889; Mixter, Amer. 

 J. of Science, [4] 19, 440, 1905 ; Roth and Wallasch, Berichte, 46, 

 896, 191 3.) 



It would appear to be very probable, on the basis of the 

 theory of the constitution of the three types of carbon 

 advanced above, that the values of any selected physical 

 property should show a regular gradation from amorphous 

 carbon to the diamond, the value for graphite lying between 

 the values for the two other forms. If we find that such a 

 gradation appears when a number of physical properties are 

 taken, we can say that this behaviour is consistent with the 

 hypothesis on which the present discussion is based, and it 

 may therefore in this sense be regarded as affording evidence 

 confirming the hypothesis. 



Below are collected the values for a number of physical 

 constants which have been determined for all three forms of 

 carbon. The numbers are taken from Landolt-BOrnstein, Tabellen, 

 4th edition, 1912. 



(1) Density 



Diamond 3*51 



Graphite 2' 10 — 2*32 



Amorphous carbon : 



Gas coke 1*885 



Cocoanut-charcoal r86o — 1*67 



Lampblack, sugar-charcoal, and wood-charcoal . 170 — r8o 



(2) Coefficient of cubical expansion 



Diamond 0*00000375 



Graphite 0*0000104 



Gas coke o'ooooi62 



(3) Thermal conductivity 



Diamond (o°C.) 0*33' 



Graphite 0*0117 



Charcoal 0*000405 



1 Eucken, Physik. Zeitschr. 12, 1005, 1911. 



