Thermodynamic prediction of vapor pressures for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and polybrominated dibenzo-p-dioxins.

The vapor pressures and thermal properties of nonmeasured polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and seven polybrominated dibenzo-p-dioxins (PBDDs) were predicted using a correlation method based on the experimental vapor pressures for 22 PCDD/Fs and octabrominated dibenzo-p-dioxin obtained by the Knudsen effusion method. The vapor pressures of all 59 PCDDs and 131 PCDFs predicted in the present study were more or less higher than the data predicted by Rordorf, although the calculation method was the same. For the most toxic 2,3,7,8-tetrachlorinated dibenzo-p-dioxin, the vapor pressure at 298 K predicted in the present study was 6.2 x 10(-6) Pa, which was 31-fold higher than the value provided by Rordorf (2.0 x 10(-7) Pa). The predicted vapor pressures for low-brominated PBDDs agreed with the data estimated by Rordorf. For 2,3,7,8-tetrabrominated dibenzo-p-dioxin, the vapor pressure predicted in the present study was 1.8 x 10(-8) Pa, obviously lower than those predicted by Rordorf.