Vapor pressure of ten polychlorinated biphenyl congeners and two commercial fluids as a function of temperature.

The Knudsen mass-loss effusion technique was used to measure the vapor pressures of commercial Kanechlor fluids (Kanechlor 300 and Kanechlor 500) and 10 major individual polychlorinated biphenyls (PCBs) in Kanechlors as a function of temperature and ortho-chlorine substitution. From the temperature dependence of vapor pressure, the thermodynamic parameters, such as enthalpies and entropies of sublimation and vaporization, were derived using the Clausius-Clapeyron equation. The results were compared with both experimental and calculated literature values. The ortho-chlorine substitution effects on the vapor pressure of major PCB congeners in Kanechlor mixtures were studied on the same homologous series. Within this series, the greater the number of chlorine substitutions in the ortho-positions, the higher the vapor pressure, because of the ortho-effect.