Thermodynamics of dibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzo-p-dioxin fromT = 5 K toT = 490 K

Author: Lebedev B.V.   Smirnova N.N.   Tsvetkova L.Y.   Iorish V.S.  

Publisher: Academic Press

ISSN: 0021-9614

Source: Journal of Chemical Thermodynamics, Vol.33, Iss.4, 2001-04, pp. : 389-403

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Abstract

In adiabatic low-pressure and dynamic calorimeters the temperature dependence of the standard molar heat capacity Cp, moof dibenzo- p -dioxin and 1,2,3,4-tetrachlorodibenzo- p -dioxin have been determined at temperatures in the range T = 5 K to T = 490 K: from T = 5 K to T = 340 K with an accuracy of about 0.2 per cent and with an accuracy of 0.5 per cent to 1.5 per cent between T = 340 K and T = 490 K. The temperatures, enthalpies, and entropies of melting of the above compounds have been determined. The experimental data were used to calculate the thermodynamic functions Cp, mo / R, 0THm o / (R·K), 0TSm o / R, and Φmo = 0TSm o - 0THm o / T(where R is the universal gas constant) in the range T → 0 to T = 490 K. The isochoric heat capacity CV, mof both dioxins has been estimated over the range T → 0 to Tfus. The effect of substitution of four hydrogen atoms by chlorine atoms on the lattice and atomic components of the isochoric heat capacity was considered.