Determination of Henry`s law constants by equilibrium partitioning in a closed system using a new in situ optical absorbance method
- Indiana State Univ., Terre Haute, IN (United States). Dept. of Chemistry
Currently, a great deal of interest exists in developing quantitative descriptions of the transport behavior for organic chemical compounds in the environment. Transport between water and air is of particular significance in this regard. A new method for measurement of thermodynamic Henry`s law constants (H) is reported. In this method, the optical absorbance of a dilute aqueous solution containing an organic compound is followed with time as the compound partitions into the air above the solution in a sealed vessel. The change in optical absorbance and the vapor to liquid volume ratio of the vessel are then used to calculate the value for H. The concentration of the organic compound in the aqueous and vapor phases need not be known. This method allows the approach to equilibrium to be observed in real time so that attainment of equilibrium is readily apparent. This method works particularly well for water-soluble compounds having low vapor pressures. The applicability of this method is limited to compounds that exhibit significant optical absorbance in the ultraviolet and visible regions of the electromagnetic spectrum. Values for H and their temperature dependencies measured using this new method are reported for methacrolein, methyl vinyl ketone, benzaldehyde, and acetophenone. Values for H are also reported for benzene, toluene, and ethylbenzene at 298 K. All reported H data are compared with previously reported values.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 675426
- Journal Information:
- Environmental Toxicology and Chemistry, Vol. 17, Issue 7; Other Information: PBD: Jul 1998
- Country of Publication:
- United States
- Language:
- English
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