179 
phases of V and of /// the metastable carbide will have to disappear 
by the following transformations: 
x FeO + Fe,C— (3 +:x)Fe + CO, . . . ‘Py 
CO, + x’Fe=C+xFeO. . « . . . Pan 
Total Fe,C — 3 Fe oe C 
These transformations, however, only then take place in the sense 
indicated above if Py>Pir. 
The situation of the points WV, /V and /// in regard to each 
other must, therefore, be that indicated in Fig. 3. 
From the equilibria indicated by the lines a, h, c ete. we can 
deduce the reactions that take place at the left and the right of 
these lines and from this find the phases that are stable in the 
different fields of Fig. 3. 
From this it appears that the carbon is only stable with gaseous 
mixtures from the region A at the right of d; at the left of d A 
reacts with the carbon dioxide with CO-formation, until the composition 
of the gas is so far modified that it can be indicated by a point 
of the line d. | 
In the region / only /Fe,O, is stable, in D Fe,O,, in C FeO and 
in B Fe. 
In the point ‘V the:3 lines c, f and e meet and separate from 
each other 3 regions, a first one A, where Fe,C. should be stable, 
a second one A, where Fe and a third one 4, where FeO should 
be «stable. Hence, the line e should be stable only from | to the 
region of higher pressures, the lines c and f only from | to lower 
pressures. 
The equilibria around the point V are however, all mestastable 
in regard to the carbon because all’ CO-coneentrations to. the right 
of are metastable. Above the line d only C and one or’ two of 
the «solid. phases Fe‚0,, Fe,O,, FeO or Fe are stable and the gaseous 
phase is metastable. 
If now we start from a mixture of Fe‚O, and C of the total 
composition g (Fig..2) and lower, at a constant temperature, the 
pressure above, gas will form of the composition / when the pres- 
sure / (Fig. 3) is .attained. If this.gas is removed by suction the 
monovariant equilibrium J is retained so long as Fe,O, is still 
present. The composition of the ferricoxide-carbon-mixture there changes 
from q tor (Fig. 2). When all the Fe,O, is used up, the pressure 
of the divariant equilibrium Fe,O,, C, gas changes according to the 
line /—/1 until at this last pressure the reduction to FeO sets in 
and when more gas is withdrawn, the pressure remains constant; 
12* 
