Manchester Memoirs, Vol. Ivi. (19 12), No. 0- 7 



sented io Fig. i in the form of curves, in which the 

 ordinates denote the equilibrium constants or the vahies 



/ •CH, 



and the abscissae the temperature. 



The values obtained with amorphous carbon are not 

 so definite as those with graphite on account of the 

 gradual transformation of the former into graphite, which 

 takes place during the course of the experiment. The 

 values in the diagram represented as amorphous carbon 

 denote samples which were heated for the first time and 

 had undergone a minimum of graphitisation. 



Couclusiois. 



The heat evolved in the transformation of carbon into 

 graphite can be calculated by means of a formula deduced 

 by Van't Hoff. In this 



(2) 





where Q,^, is the heat of reaction at the absolute 

 temperature T. R, the gas constant (198), K,i, the 

 equilibrium constant in the methane formula with 

 amorphous carbon, and K,„, that with graphite. 



It has been shown by Kirchhoff that the heat of a 

 chemical reaction changes with the temperature in the 

 following manner : 



Q,„ = Q,„-hT(C(/)-CM) 



where Q{f) is the mean specific heat of the factors (in 

 this case carbon) and C(^) that of the products of the 

 reaction (in this case graphite). 



