644 
maxima and minima. I have examined these examples, and have 
arrived at the conclusion that a maximum or minimum occurs in 
none of these reactions, and the found particularities are exclusively 
the result of errors in the observations. 
5. The equiltbria between the iron omides. 
These equilibria. play an important part in the blast-furnace 
processes. If carbon oxide is led over Fe,O,, it is reduced to FeO, 
then to metallic iron. At a definite temperature an equilibrium can 
occur between Fe,O,- and CO on one side, and FeO and CO, on 
the other side. Likewise a second equilibrium is possible between 
FeO + CO and Fe + CO,. These equilibria have been examined by 
Baur and GrässNER, and they came to the conclusion that the 
. . . . es CCO . . . 
constant of equilibrium A’ —-— possesses a maximum for the first 
CCO: 
equilibrium at a definite temperature, a minimum for the second 
at another temperature’). The found values have been reproduced 
in the graphical representation log K = f(7'-!). (See fig. 1). 
The curves which according to Baur and GLAssner represent the 
observations best, have not been indicated in the figure for the sake 
of clearness. Between the points found for the first equilibrium, 
indicated in figure 1 by triangles, a line was drawn by Baur and 
GLAssnpr. with a strongly pronounced maximum; likewise a curve 
with a decided minimum through the crosses referring to the second 
equilibrium. The two lines traced in this way do not intersect; the 
irregular situation of the points allows of a pretty great freedom 
in the tracing of these lines. The two curves mentioned divide the 
field into three regions; above the line through the crosses metallic 
iron is stable, between the two curves FeO is stable and below the 
line through the triangles Fe,O,. 
The curve through the crosses (Fe + CO, Z FeO + CO) presents 
a minimum at 680° (104 7~! = 10.493); at this temperature the heat 
of conversion is therefore zero as appears from equation 1. Baur 
and GuXssner find resp. + 8724 and — 3114 cal. at 835° and 585° 
for the heat of transformation through calculation from their line. 
Hence the heat of transformation changes over a range of temperature 
of 250° by 11838 cal. This corresponds to an algebraic sum of 
the specific heats of 47.3 eal. Such a large sum is, however, 
impossible. We can make the following estimation of this sum. 
If KorP’s law is valid, Fe and FeO will differ about 4 calories; 
!) Zeitschr. für physik. Chem. 48, 354, (1903). 
