The mean heat capacity of bismuth over 10° intervals has been determined from − 80° to 120 °C. by means of adiabatic electrical heating in a copper jacket. The maximum deviation of any individual point from a smooth curve is 0.1%, and the error in the absolute values obtained is considered to be not more than 0.1%. No discontinuities or irregularities were found; in fact, the experimental results are represented to within the limits of experimental error by the linear equation:[Formula: see text]where t is the Centigrade temperature, and the units are joules per gram per degree. The equation:[Formula: see text]was found to fit the mean experimental curve as closely as the graph could be read (0.02%). T is the absolute temperature and D(119/T) the Debye function for Cv per mole. Cp is given in joules per gram per degree. A calculation of Cp from non-thermal data gives values about 3% low.