373 
Let us at first only consider the two three-phase lines for C+-L+G 
and FeC + L + G, which are once more drawn separately in fig. 2. 
Then it is noteworthy that > and g are two quadrupie points, where 
vapour, liquid, graphite aud the carbide FeC coexist. There is, 
however, a difference between these two quadruple points, and the 
most essential difference is this that whereas in the first quadruple 
point 5 with supply of heat graphite with the vapour and the liquid 
phase is converted to FeC, in the second quadruple point the very 
reverse takes place. 
If the case supposed here actually existed, we might account for 
it in the following way. The simplest supposition we can make is 
that along the three-phase line for C + L + G the concentration of 
FeC in the vapour and in the liquid phase continually increases 
from a to 6, because the carbon concentration increases, and because 
besides we probably have here the endothermic process: 
C + Fe 2 FeC — a cal. 
In consequence of the shifting of the above mentioned equilibrium 
to the right, the liquid and the vapour phases in the quadruple 
point 6 have just become saturate with FeC, and they are still just 
saturate with graphite. With an infinitely small rise of the tempe- 
rature the two phases, which are still supposed to be in contact 
with graphite, become supersaturate with regard to FeC, and wn- 
saturate with regard to graphite, from which follows that on supply 
of heat graphite will dissolve and FeC deposit in the quadruple 
point 5, till all the graphite is gone. 
So the symbol for the conversion, which takes place in the qua- 
druple point 6 on supply of heat is as follows: 
C+ Fe Fel in the homogeneous gas- 
i) | and liquid phases. PR A ght y 
C FeC 
solid solid 
