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Environmental fate & pathways

Henry's Law constant

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Henry's law constant
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
no guideline followed
Principles of method if other than guideline:
Bubble-column and headspace technique, analysis with Nash’s fluorescence method
GLP compliance:
not specified
Specific details on test material used for the study:
- Aqueous solution with a substance concentration between 30 and 40%
- Testmaterial form: lquid
- methanol-free formaldehyde, prepared from 37% Formalin (methanol< 2 · 10-4 mol/l)
- poly(oxmethylene glycol) polymers <2%
- test material was freed of methanol stabilizer by fractional detsillation
2 970 other: M atm-1
25 °C
0.034 Pa m³/mol
25 °C

value corresponding to 0.034 Pa · m³/mol


The substance will not evaporate into the atmosphere from the water surface.
Executive summary:

In an experimental study was conducted to assess the Henry’s law constant of the test item. The Henry’s law constant was determined as a function of temperature by bubble-column and by head-space techniques. The constant was determined to be 2970 M atm-1 this corresponds to a value of 0.034 Pa*m³/mol. Therefore, no evaporation of the test item from the water surface into the atmosphere is expected.

Description of key information

The substance will not evaporate into the atmosphere from the water surface.

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):
at the temperature of:
25 °C

Additional information

The experimental value for the Henry’s law constant (HLC) of 0.034 Pa·m3 mol-1 at 25 °C (Betterton, 1988) indicates that volatilization from an aquatic environment into the atmosphere is unlikely under environmental conditions.

This is supported by the experimental data of Zhou et al., 1990 which revealed a HLC of 0.029 Pa*m³/mol and the calculation from experimental data by Straudinger et al., 2001. Based on different experimental valued a HLC was determined by best-fit estimation to be 0.021 Pa*m³/mol.

All experimental and calculated values are within the same range and underline a low HLC. Therefore no evaporation of the test item from water surfaces to atmosphere is expected.