140% 
other as solid phases. On addi- 
tion of oxygen the lowest oxide, 
ferrous oxide, may occur side by 
side. These three solid phases form 
then with the gaseous phase the 
monovariant equilibrium II. 
Besides this monovariant equili- 
brium there are still possible two 
others, namely that between 
FeO, Fe,O,, C and gas (II) and 
that between Fe,O,, Fe,O,, Cand 
gas (I). 
If we start from a mixture of C and F, O, of the composition q, 
on withdrawal of gas, these monovariant equilibria will be attained 
in the order I, II, IU, where the composition of the solid phases 
mixture changes in the direction g-r-s-t and the following reactions 
take place (the empirical composition of the gaseous phase to be 
taken as CO): 
x = . Fy] @ \ 1 a 
I. Phases: C,Fe,O,,Fe,O,, gas. Reaction: 3Fe,0,-+-—C22k e,0, + — CO, 
=, x 
. Nn Lye 
I. ,, ©€,Fe,0,,FeO, gas » FeO, + -C 23 FeO ae CO; 
=o ie : 
eee aN ie : 1 
i lege ee C,FeO,Fe, gas » FeO+—C Fe + —CO,, 
i Xs X3 
In addition, with the metastable carbide as participating phase, 
other metastable equilibria may be thought possible, of which the 
principal ones are *): 
) \ A \ = DJ = « A 5 3 EE + 1 3 N 
IV. Phases: C,FeO,F,C, gas. Reaction: 3FeO + 1 Ge ty COx, 
4 4 
V. »  FeO,Fe,C,Fe,gas ,, x,FeO : Fe,Co(38+x,)Fe + CO,x, 
These monovariant equilibria are to be considered as the limits 
within which the following divariant equilibria are stable: 
a. Phases: Fe,O,, Fe,O,, gas. Reaction: CO+3Fe,0,722Fe,0,+CO0, 
b. x Fe,O,, FeO, gas. by CO+ Fe,0,273 FeO +CO, 
G. 5 FeO, Fe, gas. 5 CO+ FeO = Fe —+C0, 
d. 7 C, gas. ss CPE ACO, 22C0. 
1) It might also be possible that after the equilibrium 1 followed at once an 
equilibrium with FegC, hence between the phases Fes0,, C, Fe; and gas, then the 
equilibrium between the phases FezC, Fes0,, FeO and gas and finally that between 
Felis, FeO, Fe and gas. It would, however, lead us too far to discuss all these 
eventualities separately. 
12 
Proceedings Royal Acad. Amsterdam. Vol. XIX. 
