Abstract: A new precision rotating-bomb calorimeter has been built. It can be operated in the isoperibol or in the adiabatic mode. The data of the measured temperature could be collected automatically by a microcomputer and the result of determination could be calculated by using appropriate software. In the isoperibol mode, the apparatus was calibrated by using NBS39i benzoic acid with a standard deviation of the mean of ±0.006%. The combustion energies of hippuric acid and acetanilide have been determined to be -(23 542.7±0.9) J/g and-(31 245.8±2.4) J/g(mean and its standard deviation) respectively. The uncertainties of these results were estimated as twice the overall standard deviation of mean, to be ±4.5 J/g and ±7.5 J/g, respectively. These results are in agreement with the recommended values. The properties of the two compounds as the reference materials for combustion calorimetry concerning compounds containing C, H, O and N with a low nitrogen content have been discussed.

Key words: Energy of combustion, Hippuric acid, Acetanilide, Reference material, Rotating-bomb calorimeter