3614. WATASE, T. Heat of Formation of Cementite. Sci. Repts. T˘hoku Imp. Univ., vol. 17, 1928, pp. 1091-1109; Chem. Abs., vol. 23, 1929, p. 1046.
Cementite prepared by subjecting plates of C steel (2% C) to electrolysis with N HCl and a current density of 0.075 amp. per cm.,2 was burned in a Berthelot-Mahler bomb calorimeter, and its heat of combustion was determined. From the observed amount of heat evolved and the composition of the combustion residue, the heat of the reaction Fe3C+3 O2=Fe3O4+CO2 was found in the literature for the formation of Fe3O4 and for CO2, the heat of formation of cementite is calculated to be -4.8 kcal. at 20░.