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Environmental fate & pathways

Henry's Law constant

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Description of key information

Staples et al. (2008) conducted a literature review with regard to Henry Law Constant (HLC) of Nonylphenol (NP). The value for HLC reported in the EU Risk Assessment report, 2002, was estimated by calculation.

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):
11.02
at the temperature of:
20 °C

Additional information

HLC has been reported for NP ranging widely from about 0.08 to 11.02 Pa m 3 /mol at 20 to 25 °C (Dachs et al. 1999; Mackay 2001a; EC 2002; Lalah et al. 2003;all references cited in Staples, 2008). From these data, Mackay (2001a) estimated a value of 2.84 Pa m³ /mol for use in multimedia modeling.

The calculation reported in the EU Risk Assessment report, 2002, is based on the vapour pressure, molecular weight and water solubility of the substance using the following equation:

HENRY = VP • MOLW / SOL

Explanation of symbols:

- VP = vapour pressure [Pa]

- MOLW = molecular weight [g/mol]

- SOL = solubility [mg/l]

- HENRY = Henry's law constant [Pa m³/mol]

Using a vapour pressure of 0.3 Pa, a molecular weight of 220.34 g/mol and a water solubility of 6 mg/l gives a Henry’s law constant for nonylphenol of 11.02 Pa m³/mol.

This calculated value is in agreement with the experimental value cited in Staples et al. (2008) and should be used as key value for chemical safety assessment.