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Physical & Chemical properties

Dissociation constant

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Description of key information

The dissociation constant of Tri-n-Butylamine in water was measured by conductometry. The pKa at 25° is 10.89 and 11.04 at 18 °C. The pKa at 20°C was calculated using the temperature coefficient of -0.021 as given in Damsgaaard-Sorensen and Unmack (1935): 10.998 rounded to 11.0.

Due to the low water solubility of the test substance correction for dissolved carbonate were carried out. This was necessary, because at low concentrations, conductivity will be influenced significantly by dissolved carbonate and hydrogen carbonate and falsify results for pKa determination. Measurements were performed at 18°C.

In the supporting study (OXEA, 2009), a determination according to the titration method was not feasible due to the low water solubility of the submission susbstance.

Key value for chemical safety assessment

pKa at 20°C:
11

Additional information

The following results were determined from the key study:

pKa at 20°C: 10.998 (from temperature coefficient of -0.021 as given in Damsgaaard-Sorensen and Unmack (1935), rounded to 11.0

pKa at 18°C (Damsgaaard-Sorensen and Unmack, 1935): 11.04

pKa at 25°C (Damsgaaard-Sorensen and Unmack, 1935): 10.89