387 



o 



o 



FE+HgV^ 



'3Q»+Q 



Fig. 1. 

 O71 the mixture of the solid phases Fe^Oj and FefO^. 



Now the question presents itself vvhellier there exists also a three- 

 phase line for Fe,0, + Fe^O^ + G '). 



SosMAN and Hostetter ') think that they have 10 derive from their 

 determinations about the tension of dissociation and the diffraction 

 of light of mixtui-es Fe^Oj + FejO^ that the oxides Fe^O^ and Fe^O^ 

 in the solid state are niiscible if not in all proportions, yet very 

 near the concentration F3O4. If there really existed a continnous 

 nnxed crystal series here, there would not appear a three-phase 

 curve for FejOj -f" ^^'^s^^ ^^ Gr» ^"d the figure discussed here would 

 be complete. 



It is, however, the question whether on the ground of Sosman 

 and Hostetter's researches we may conclude to a continuous mixed 

 crystal series. When we draw up a /;,.r-section of the system 

 oxygen-iron corresponding to the temperature 1100°, on the 

 assumption that Fe^O, and FcjO^ are only miscible to a limited 

 degiee in the solid state, we arrive at the schematic i-'epresentation 

 drawn in fig. 2. 



In this /;,,i'-section, in which it is assumed that the oxides present 

 a certain mixture in the solid state, the line d f represents the 

 mixed crystals that are rich in Fe^Oj, and which coexist with the 

 vapours 6 e, the line g h referring to mixed crystals rich in Fe,0^, 

 which can coexist with the vapours eh. 



k point on the line df, here />, corresponds with the concen- 

 tration Fe^Oj, and thus a point of the line g h, viz. q, corresponds 

 with concentration Fe„0^. 



It follows immediately from this what curve we must get, when 



1) These Proc. 19, 175 (1916) Reindkrs has supposed the existense of such an 

 equilibrium but the results of the experiments of Sosman and Hostetter, were 

 unacquanted at that lime. 



2) Journal Amer. chera Sec 38, 837 (1916). 



