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Physical & Chemical properties

Partition coefficient

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Description of key information

Partition coefficient (LogPow): 0.06 as trimellitic anhydride
Partition coefficient (LogPow): 0.54 as trimellitic acid (non-ionized)
Partition coefficient (LogD): -4.83 as trimellitic acid (ionized, environmental conditions)

Key value for chemical safety assessment

Log Kow (Log Pow):
0.54
at the temperature of:
20 °C

Additional information

The octanol/water partition coefficient of trimellitic anhydride (TMA) has been determined experimentally by the HPLC method. The log Kow obtained in this way is 0.06 (Villa, 2010c). QSAR modelling performed with the KOWWIN program of the US EPA gives a log Kow estimate of 1.95 for TMA.

Trimellitic anhydride undergoes almost instantaneous hydrolysis on contact with water, to form trimellitic acid (TMLA).

The octanol/water partition coefficient of trimellitic acid (TMLA) has been determined experimentally by the Shake Flask method. The log Kow obtained in this way is 0.54 (Nichetti, 2014). QSAR modelling performed with the KOWWIN program of the US EPA gives a log Kow estimate of 0.61 for TMLA.

Considering all the charge-state forms of trimellitic acid dissolved in water and in octanol, a LogD (distribution coefficient) was estimated taking account for the pH dependence of the substance in aqueous solution.

For the environmental and PBT assessments, trimellitic acid was therefore considered more significant, with logD= -4.83.