There are reviewed the existing data on the entropies of oxygen, carbon dioxide, graphite, and diamond, and those on the heats of combustion of natural and artificial graphite and of diamond, includin §" the results recently obtained in a joint investigation by the National Bureau of tandards and the Coal Research Laboratory of the Carnegie Institute of Technology. The new thermochemical data are combined with values of the entropies to obtain values for the heat and free energy of formation of carbon dioxide, and for the transition between graphite and diamond.For C (c, graphite) +02 (g) =C02 (g), at 25° C, per mole, .1Ho 355 ±46 NBS international joules,030 ± 1l calories,228