title: Air-water partition constants for volatile methyl siloxanes.
abstract: Silicones are an important class of hydrophobic compounds in widespread use. To evaluate their fate in the environment, an accurate value of the air-water partition (Henry's law) constant is necessary, which, unfortunately, is lacking at present. A static head space and a newly developed dynamic vapor entry loop method were used to obtain the air-water partition constant for six volatile methyl siloxanes. Internally consistent data were obtained. The value of Henry's constant, as calculated from pure component vapor pressure and aqueous solubility, was 10- to 170-fold greater than the experimental values. A correction to the Henry's constant that involves the ratio of the thermodynamic activity coefficient for a methyl siloxane at infinite dilution to that at saturation solubility in the aqueous phase is proposed.
authors.affiliation: Institute of Experimental Meteorology, TYPHOON, Kaluga Region, Russia.
authors.forename: A
authors.initials: A
authors.lastname: Kochetkov
authors.forename: J S
authors.initials: JS
authors.lastname: Smith
authors.forename: R
authors.initials: R
authors.lastname: Ravikrishna
authors.forename: K T
authors.initials: KT
authors.lastname: Valsaraj
authors.forename: L J
authors.initials: LJ
authors.lastname: Thibodeaux
mesh_terms: D004785:Environmental Pollutants / Q000032:analysis*; D008962:Models, Theoretical; D011312:Pressure; D012833:Siloxanes / Q000737:chemistry*; D012995:Solubility; D014835:Volatilization
chemical_list: D004785:Environmental Pollutants; D012833:Siloxanes