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Environmental fate & pathways

Henry's Law constant

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Description of key information

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):
33
at the temperature of:
12 °C

Additional information

The Henry's Law constant (H) is calculated as 69.8 Pa m3/mol (log H = 1.84), based on a vapour pressure of 33 kPa at 25 °C and a water solubility of 42,000 mg/l at 25 °C in EUSES.

The Henry's Law constant (H) is calculated as 59.8 Pa m3/mol (log H = 1.78), based on a vapour pressure of 270 hPa at 20 °C and a water solubility of 42,000 mg/l at 20 °C (Howard, 1990). The calculated H value indicates that MTBE has the potential to volatise rapidly from water to air. Additional calculated values are also available, 43.8 Pa m3/mol (log H = 1.64) at 20°C and 53.5 Pa m3/mol (log H = 1.73) at 25 °C (Robbins et al., 1993) and 55.3 Pa m³/mol at 20 °C (Finnish Environment Institute, 1999).

The value of 69.8 Pa m3/mol at 25 °C corresponds to 33.3 Pa m3/mol at environmental temperature; the latter will be used in the assessment.