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Measurement of temperature dependence for the vapor pressures of twenty‐six polychlorinated biphenyl congeners in commercial Kanechlor mixtures by the Knudsen effusion method
Author(s) -
Nakajoh Katsuhiko,
Shibata Etsuro,
Todoroki Tomohiro,
Ohara Atsushi,
Nishizawa Katsushi,
Nakamura Takashi
Publication year - 2006
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/05-215r.1
Subject(s) - knudsen number , polychlorinated biphenyl , environmental chemistry , vapor pressure , biphenyl , chemistry , effusion , thermodynamics , organic chemistry , physics
Abstract The vapor pressures of the major congeners in commercial polychlorinated biphenyl (PCB) mixtures (Kanechlors; Kanebuchi Chemical Industry, Tokyo, Japan) have been experimentally determined by Knudsen mass loss effusion. We obtained vapor pressures for the individual PCBs in the crystalline solid, liquid, and subcooled liquid forms as a function of temperature. We derived the thermodynamic parameters, such as the enthalpies of sublimation and vaporization, from the temperature dependence of the vapor pressure by the Clausius–Clapeyron equation. To decide whether the commercial PCB mixtures were ideal solutions, we obtained the activity coefficients by comparing our experimental vapor pressures for pure PCB congeners with those calculated from Kanechlor molar compositional data and vapor pressure values. In many cases, we found that, at 298 K, the values of the activity coefficients of major PCBs in Kanechlor 300 and 500 ranged from 1 to 2. Thus, we suggested that the commercial PCB mixtures show slight positive deviations from ideal solution (Raoult's Law) behavior at ambient temperatures.