Enthalpies of combustion at 298.15 K were measured by rotating bomb calorimeter for 1,2,3-trichlorobenzene (1), 1,2,4-trichlorobenzene (2), and 1,3,5-trichlorobenzene (3), and the standard enthalpies of formation derived for these compounds in their liquid or solid and gaseous states. The results of -DHc0 (1 or s), -DHf0 (1 or s), and DHf0(g) in kJ.mol-1 are 2793.76 ?1.63, 66.91 ?1.67, 8.23 ?1.83 for 1; 2810.46 ?1.45, 50.21 ?1.49, 4.85 ?1.57 for 2; 2785.42 ?1.29, 75.25 ?1.34, -2.57 ?1.43 for 3 resp. The enthalpies of isomerization of these compounds in their gaseous states calculated are given: 1 ?2, DHi = 3.38 kJ.mol-1; 1 ?3, DHi = 10.80 kJ.mol-1; 2 ?3, DHi = 7.42 kJ.

Key words: ORGANO CHLORIDE COMPOUNDS, ENTHALPY OF FORMATION, ENTHALPY, CALORIMETRY, TRICHLOROBENZENE, CHLOROBENZENE P, COMBUSTION HEAT, THERMOCHEMICAL PROPERTY, ISOMERIZATION