Properties

In the pure form, PCDDs are colorless solids or crystals. 2,3,7,8-TCDD is odourless. The odours of the other PCDDs are not known.

Monochlorodibenzo-p-dioxins Dichlorodibenzo-p-dioxins Trichlorodibenzo-p-dioxins Tetrachlorodibenzo-p-dioxins
Molecular mass 218.6 253.1 287.5 322
Density (g/dm3) No data No data No data 1.827
Melting point (°C) 89.0-105.5 114-210 128-163 175-306
Boiling point (°C) No data No data 374 446.5
Soil sorption coefficient (log Koc) No data No data No data No data
Octanol/Water Partition  (log Kow) 4.52-5.45 5.86-6.39 6.86-7.45 6.6-8.7
Solubility in water in 25 °C (mg/dm3) 0.278-0.417 3.75*10-3-1.67*10-2 4.75*10-3-8.41*10-3 7.9*10-6-6.3*10-4
Vapour pressure at 25 °C (mm Hg) 9.0*10-5-1.3*10-4 9.0*10-7-2.9*10-6 6.46*10-8-7.5*10-7 7.4*10-10-4*10-3
Henry’s law coefficient (KH) atm*m3/mol 82.7*10-6-146.26*10-6 21.02*10-6-80.04*10-6 37.9*10-6 7.01*10-6-101.7*10-6
Pentachlorodibenzo-p-dioxins Hexachlorodibenzo-p-dioxins Heptachlorodibenzo-p-dioxins

Oktachlorodibenzo-
p-dioxins

Molecular mass 356.4 390.9 425.3 459.8
Density (g/dm3) No data No data No data No data
Melting point (°C) 195-206 238-286 265 330-332
Boiling point (°C) No data No data 507.2 485-510
Soil sorption coefficient (log Koc) No data No data No data No data
Octanol/Water Partition  (log Kow) 8.64-9.48 9.19-10.4 9.69-11.38 8.78-13.37
Solubility in water in 25 °C (mg/dm3) 1.18*10-4 4.42*10-6 2.4*10-6-1.9*10-3 2.27*10-9-7.4*10-8
Vapour pressure at 25 °C (mm Hg) 6.6*10-10 3.8*10-11 5.6*10-12-7.4*10-8 8.25*10-13
Henry’s law coefficient (KH) atm*m3/mol 2.6*10-6 44.6*10-6 1.31*10-6-2.18*10-5 6.74*10-6

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