182 
When instead of the stable carbon the metastable Fe,G oecurs, 
metastable equilibria are formed in the field A. The line / does not 
then terminate already in VI, but ends in the point VIII where it 
cuts the line ¢ and where. there is consequently monovariant equi- 
librium between FeO, Fe,C, FeCy and gas. The region of the mixed 
crystals F thus becomes larger also and is limited on the one side by 
the line /, on the other side by a cubic hyperbole m, which passes 
through CO and VIIL and indicates the equilibrium of the reaction 
8 l 
SSPE YN CO, = | —— | Fe,0 2 CO 
Gd 
p eee 2 
== PE Kn 
PCO,, l—«# 
hence, 
To the right of this line Fe,C is then stable. 
The isotherm for temperatures between TO00° and 880°. 
Whereas above 880° all mixed crystals from pure iron to the 
ones most rich in carbon are stable, this is no longer the case below 
880°. Those poor in carbon become metastable and only those whose 
composition is situated between two limits — indicated in Fig. | 
by, the letters « and / are stable. 
Hence, the isotherm gives 4 monovariant equilibria, namely: 
J? Fe;O,, Fe;O;, O ‘and “gas 
II. Fe,O,, FeO, C and gas 
VI. FeO, (FeC,),, C and gas 
VII. FeO, (FeC,),, Fe and gas. 
