3158.     SELTZ, H., McDONALD, H. J., AND WELLS, C.  Heat Capacity of Iron Carbide 68°-298° K. and the Thermodynamic Properties of Iron Carbide.  am. Inst. Min. and Met. Eng., Tech. Pub. 1137, 1939, 11 pp.; Chem. Abs., vol. 34, 1940, p. 1904.

        Heat capacities of Fe₃C were determined experimentally 68°-298.1° K.  the entropy was calculated S_298.1=25.7 (±1) e. u.  From the solubility curves of Wells for C and Fe₃C (β) in austenite, the free energy and heat of formation of carbide are evaluated.  At 298.1° K., ∆H=5,800 cal., ∆F°=4,700 cal. for the formation of Fe₃C (a) and S_208.1=24.7 e. u.  The temperature at which ∆F°=0 for 3 Fe (γ)+C (graph.)=Fe₃C (β) is 1,082° K.