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Environmental fate & pathways

Henry's Law constant

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Description of key information

Henry's Law constants for terephthalic acid were estimated using the HENRYWIN v3.20 QSAR model available from the US EPA. Estimated Henry's Law constants of 2.21E-7 and 3.93E-8 Pa m3/mole at 25 degrees C were obtained by the bond estimation and group estimation methods, respectively.

Key value for chemical safety assessment

at the temperature of:
20 °C

Additional information

After conversion to log10, the estimated Henry's Law constants (HLc) for terephthalic acid range from ca. -7 to -8. According to the tables presented in Appendix II of Part II of the Technical Guidance Document on Risk Assessment (European Commission, 2003), the threshold value of log10 HLc at which significant (=/>10%) air-stripping occurs under conditions of forced aeration during waste-water treatment is +1.0, and no air-stripping occurs at log10 HLc values =/<1.0. Both HLc estimates provided by HENRYWIN v3.20 indicate that terephthalic acid is unlikely to partition from aqueous systems to the atmosphere.