Chemistry. — ''On the Si/stei)i /ron-0.rf/gen'\ By Prof. A. Smits 

 and J. M. Bjjvoet. (Communicated by Prof. S. Hoogewerff). 



(Communicated in the meeting of June 29, 1918). 



The equilibria lo wliicfi the reactions between iron-oxides and 

 reducing gases as carbon oxide and hydrogen give rise, have 

 ah-eady repeatedly been a subject of a scientific research. 



Thus of the gas phase of the three-phase equilibria FeO -f- Fe -|- G 



and Fe,0^ -|- FeO -f- Gr the ratio 7füY\ '"^^P- /uTvT ^^'^^ studied ^). 



(ÜUJ ("s^) 



Three-phase systems of three components were studied, i.e. systems 

 that were monovariant at constant pressuie. In this there was, however, 

 no need (o keep the pressure constant, because the above-mentioned 

 relations are inde|)endent of this. As result the researches with 

 CO as reducing gas yielded two equilibrium curves, which may 

 be called three-phase curves foi- the homogeneous equilibrium 

 in the gas phase which coexists with two solid phases, namely one 

 for FeO + Fe + G, and another for FejO, -f- FeO ~\- G, of which 

 ScHEFFER ') showed that they had to intersect in virtue of the heat- 

 effect of the conversions. 



Researches with H^ as substance of reduction did not only give 

 the situation of the three-phase line for Fe -|- FeO -{- G, but also 

 that for Fe + t GjO^ -|- G. The latter was made probable by Reinders, 

 who also computed the situation of the ilnee-phase line for FegO^ 

 -[- FeO -|- G in this system from the corresponding line for the reduction 

 with CO by the aid of the water-gas equilibrium. When we trace 

 the three-phase curves for FejO, + FeO -|- G and for FeO + Fe + 

 G for the case G = CO -f- COj, we get the following figure when 

 log K is drawn as function of T, in which figure a third three- 

 phase line for Fe -[- Fe^O^ -j- G must slart from the point of inter- 

 section, which is here a quadruple point as Scheffer has noticed. 



') A survey of the literature of these researches has been given in Reinders' 

 paper on: the equilibria of iron-oxide wiUi hydrogen and water vapour. Ghem- 

 Weekblad 16, 180- (li)18K 



») These Proc. Vol. XIX, p. 63Ü. 



