3752.     ---------------.  [YAP, C. P.]  Thermodynamic Study of the Phasial Equilibria in the System:  Iron-Carbon.  Am. Inst. Min. and Met. Eng., Tech. Pub. 381, 1931, 26 pp.; Chem. Abs., vol. 25, 1931, p. 1148.

        Previously published Fe-C diagrams are reviewed and the disagreements regarding the shapes of the liquidus and solidus are pointed out.  The Fe-C diagrams were replotted and C was calculated as mol. % and as mol. % Fe-C.  Thermodynamic laws of solutions that apply to a diagram of this type were calculated and values taken from the various Fe-C diagrams were substituted to determine which was the more nearly correct.  The results indicated that in the liquid state C exists mainly as Fe3C, but in the solid γ-Fe it is dissolved as C.  The correct liquidus bounding the field ∆+melt is probably that of Ruer and Goerens (Chem. Abs., vol. 12, 1918, p. 2524), which is slightly convex.  In the ∆-field, C is dissolved as such in the melt.  Heat of transition of γ- to ∆-Fe is about 2.0 cal, per gm. and accordingly the heat of fusion of γ-Fe is about 64.4 cal. per gm.