178 
Metastable are the equilibria: 
ve. Phases: FeO, Fe,C, gas. Reaction: 3FeO+5COZFe, C+4C0, 
bf e Fe,C, Fe, gas. »  Fe,C++CO, = 3Fe + CO. 
According to the law of mass action, when the gas consists of « 
mols. of CO and (1—.2) mol. of CO, and when P is the total 
pressure, the following relations should apply to these equilibria: 
PCO v 
a —<—<_—_——_ ed = ka 
PCO» l—«z 
DC x 
b. ad = —— == fy 
PCO, l—w« 
DC a 
HEE sails as 
PCO. l—a 
p?co x 
d == B ks 
PCO, l—«a 
p'co a 
e. =e = 
pico,  (1-«)* 
200 x? 
if ee = F == ky 
PCO. l—wx 
If in accordanee with R ScHENCK *) 
we represent the relation between « 
and P graphically there are formed 
a series of lines as indicated in Fig. 3. 
The lines a, h and c are straight: 
in these equilibria « is independent 
of the pressure. The lines d and f ©% 
are cubic hyperboles aud e isa simi- Fig. 3. 
lar curved line of higher degree. The monovariant equilibria are 
now found as points of intersection of these lines, namely /, if 
and /// as points of intersection of a, 6 or ¢ with d, /V as point 
of intersection of d and e and V as that of c, f and e. 
The equilibria /V and V are metastable because this is the case 
with one of the participating phases, fe,C. From this it may be 
directly concluded that V must lie above /// and /V below the 
same. As V and /// are both situated on the line c the composi- 
tion of the gaseous phase for these equilibria is the same. When 
now this gaseous phase comes alternately in contact with the solid 
a 
1) R.-Scuencx, Zeit. angew. Chem. 17, 1077 (1904); Z. f. Elektroch. 15, 584 
(1901); Physikalische Chemie der Metalle, Halle a. S. (1908). 
