Experimental determination of the enthalpy of formation of dibenzo- p-dioxin

Abstract

The standard molar enthalpy of combustion of dibenzo- p -dioxin (DD) was measured at T= 298.15 K by static-bomb combustion calorimetry: ΔcHmo(cr) =−(5723.8 ± 1.4)kJ · mol−1. The standard molar enthalpy of sublimation of this compound was measured by microcalorimetry: ΔcrgHmo= (91.45 ± 0.76)kJ · mol−1. These values were used to derive the standard molar enthalpies of formation of DD in the crystalline and gaseous states: ΔfHmo(cr) =−(141.6 ± 2.1)kJ · mol−1and ΔfHmo(g) =−(50.1 ± 2.2)kJ · mol−1. The specially obtained sample of DD of high purity {mole fraction x= (0.9999 ± 0.0001)} was used in all measurements.