875 
the influence of the temperature on the homogeneous equilibrium on 
rise of temperature. 
Thus we may not conclude from the circumstance that the trans- 
formation (2), which refers to the second quadruple point g is endo- 
thermic, that the conversion in the homogeneous phase proceeds 
endothermically in the direction of the arrow. 
If we make the same supposition as we did just now, viz. this 
that in the process of evaporation resp. melting of FeC more heat 
is absorbed than is developed by the process of condensation resp. 
solidification of graphite, the total heat of transformation (2) might 
be endothermic, also when the homogeneous process in the direction 
of the arrow was exothermic. 
In the opposite case, however, the reaction in the homogeneous 
phases in the direction of the arrow would certainly be endothermic. 
Thus we come to the conclusion that the case of inverse depo- 
sition of solid phases supposed here is possible, when the conversion : 
C+ Fe Fe © 
taking place in the homogeneous phases between the points g and 5 
has become less greatly endothermic or exothermic. 
As is known, a change in the heat-effect with the temperature is 
a phenomenon of general occurrence, which owes its origin to the 
circumstance that the specific heat is a function of the temperature. 
Repeatedly great changes of the heat of reaction with the temperature 
have been observed, so much so that a reversal of the sign of the 
heat took place, from which accordingly follows, that the possibility 
of the here supposed case was to be expected on the ground of our 
present knowledge. 
Now we shall proceed to the discussion of the other three-phase 
lines, which likewise start from the two quadruple points 6 and g. 
In the first place a three-phase line for C + Fe C + G still starts 
from the point 6. To determine the direction of this curve we may 
make use again of VAN per Waars’ theory of binary mixtures. 
If we denote graphite by 5, and carbide by S,, the following 
relation follows from the theory mentioned for the three-phase line 
for C+ FeC+G: 
Te ig ce wee W. 
É 519 Sod 
T & | ee Eel: Us, — dg (L) 
dT) Ss S;G ae Bs, Og 7 : 
sig eS $29 
In the quadruple point 4 numerator and denominator indicate the 
