2214.     MAXWELL, H. L., AND HAYES, A.  Free Energy and Heat of Formation of Iron Carbide for the Temperature Interval 650°-700°.  Jour. Am. Chem. Soc., vol. 48, 1926, p. 584-593; Chem. Abs., vol. 20, 1926, p. 1349.

        Equilibrium constants for the reaction 3Fe(a)+2CO=CO₂+Fe₃C were measured at 1 atm.; a flow method was used and resultant gases were analyzed.  The volume % CO₂ at equilibrium was 35.7±0.1 at 650°, 25.25±0.05 at 700°.  From data of Rhead and Wheeler for equilibrium constants of reaction 2CO=C (graphite)+CO₂, ∆F for reaction 3Fe(a)+C=Fe₃C is 3,138 cal. at 650° and 2,281 cal. at 700°.  These data give ∆H at 675°=19,162 cal.