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Environmental fate & pathways

Henry's Law constant

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Description of key information

Measurement of the Henry’s Law constant of the substance was reported in the literature by Arp and Schmidt (2004)

KAW (dimensionless) = 0.0709 at 20 °C

H (Pa.m3/mol) = 173 at 20 °C

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):
173
at the temperature of:
20 °C

Additional information

Measurement of the Henry’s Law constant of the substance was reported in the literature by Arp and Schmidt (2004). The procedure used was a static equilibrium approach based on a variable headspace technique. Six glass vials of known volume were filled to different levels with an aqueous solution of the substance so that the headspace to aqueous phase volume ratios ranged from about 1 to 20. The vials were then incubated at various temperatures for at least 3 hours, and the headspace concentration analysed by GC-FID. By plotting the inverse of the GC-FID peak area for each of the 6 headspace ratios at each temperature against the headspace to aqueous phase volume ratio, the dimensionless Henry's Law constant (KAW) at ambient pressure were determined. The dimensionless KAW values determined, together with the equivalent values for Henry’s Law constant (H) with the units Pa.m3/mol calculated from KAW = H/RT are tabulated below:

Temperature

10 ºC

20 ºC

25 ºC

30 ºC

40 ºC

KAW (dimensionless)

0.0311

0.0709

0.1050

0.1407

0.2605

H (Pa.m3/mol)

73.2

173

260

355

678

 

The Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint Specific Guidance, Appendix R.7.1-4 indicates that substances with a Henry's Law constant of around 100 Pa m3/mol will volatilise from water rapidly.