This paper presents thermodynamic data in graphical form to be used in determining adiabatic flame temperatures for combustion processes at atmospheric pressure. The data are applicable for coal, coke, and liquid and gaseous hydrocarbon fuels when burned with air at values of excess air ranging from 0 to 100 per cent. A technique for using electronic computing machines to calculate the equilibrium composition and enthalpy of gaseous products of combustion is discussed. The data are presented in a generalized form so that the heat of dissociation and total enthalpy can be determined for any gas composition within the range considered and for any temperature between 2400 and 4000 F. Conversely, the adiabatic flame temperature may be determined if it lies between these limits and if the enthalpy of the system is known. Plots of the heat of dissociation of flue gases permit the determination of flame temperature with an accuracy of ±20 F by means of additional calculations and auxiliary plotting. Simplified plots of total enthalpy enable the flame temperature to be determined directly with an accuracy of ±75 F. Although only four gas components, CO2, H2O, O2, and N2 were considered, it is unlikely that minor constituents will affect the results appreciably. Trial calculations showed that the error introduced by including SO2 with CO2 when burning a high-sulphur coal amounted to less than 10 F at extreme conditions of temperature and excess air.