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Diss Factsheets

Physical & Chemical properties

Surface tension

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Description of key information

The surface tension of L-leucine was addressed in several publications available in the literature. These experiments showed that L-leucine behaves as a surface-active substance and the surface tension is ca. 71.6 mN/m at 20°C for an aqueous L-leucine solution at a concentration of 7.0 g/L.

Key value for chemical safety assessment

Surface tension:
in mN/m at 20°C and concentration in mg/L:
7 000

Additional information

There are 3 studies available that assess the surface tension of L-leucine in aqueous solutions. None of these studies was performed according to internationally accepted testing protocols or GLP, but the methods that were used were acceptable and the publications contain sufficient information to assess the quality of the experiments.

The outcome of the different studies are in good agreement with one another.

In a first publication the surface tension of aqueous solutions of L-leucine as function of temperature and concentration was measured using the drop volume method. L-leucine was found to behave as a surface-active substance. It forms a gaseous adsorbed film at the air/water surface at concentrations up to 0.059 mol/kg. At higher concentrations, an expanded state film is formed.

The surface tension was found to be ca. 71.6 at 20°C at an L-leucine concentration of 0.053 mol/kg in water (value deduced from graph).

In a second set of experiments, the surface tension of a solution of a 0.0497M solution of L-leucine in 0.10M aqueous NaCl was assessed using the differential capillary-rise method.

The surface tension of a 0.0497 molar solution of L-leucine in 0.10M aqueous NaCl was found to be ca. 70.1 mN/m.

Finally, in a third publication, the surface tension of L-leucine in aqueous solution was measured using the Wilhelmy plate method and was found to be ca. 67 mN/m for a 0.14M aqueous L-leucine solution (value deduced from graph).