Registration Dossier

Physical & Chemical properties

Partition coefficient

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Description of key information

The substance has surface-active properties and OECD 107 method suggests that “when the shake flask method is not applicable, e.g. for surface active materials, a calculated value or an estimate based on the individual n-octanol and water solubilities should be provided”.

With the cmc value and the density a valid log Kow can be calculated to be 1.57.

Key value for chemical safety assessment

Log Kow (Log Pow):
1.57
at the temperature of:
20 °C

Additional information

The registration substance has a measured log Kow of 0.87 by using OECD107 Shake-flask method.

OECD 107 method suggests that “when the shake flask method is not applicable, e.g. for surface active materials, a calculated value or an estimate based on the individual n-octanol and water solubilities should be provided”. 

For surface active substances, like the registration substance, which can form micelles and show a complex solubility behaviour, due to aggregation, the monomer concentration, and hence the thermodynamic activity, reaches a limiting value at the critical micelle concentration (cmc). It remains approximately constant when the total concentration is further increased. For ecotoxicological models requiring a solubility value, the critical micelle concentration is therefore the appropriate parameter. This is also suggested in ECHA Guidance R.7a.

The measured cmc value of the registration substance is 28.2g/L at 25°C.

As the substance is fully miscible in every ratio with n-octanol the density can be used as a quantitative descriptor of the solubility in n-octanol. This certainly constitutes a worst case assumption, since the maximum solubility is taken as 100 % test substance.

The measured density of the substance is 1.0382 g/cm³ at 20°C.

With the cmc value and the density a valid log Kow can be calculated to be 1.57.