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Physical & Chemical properties

Vapour pressure

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Description of key information

Experimental data for tetraammonium ethylenediaminetetraacetate is only available in aqueous solution. Read across to editic acid was done instead, as a vapour pressure determinedfor the aqueous solution would result in values reflecting the vapour pressure of H2O.
The vapour pressure of edetic acid was determined to be 2E-012 hPa at 25°C according to Riedel and Plank.

Key value for chemical safety assessment

Additional information

As the substance is only stable and handled in aqueous solution, no experimental data with the pure tetraammonium ethylenediaminetetraacetate is available. Measurements with the aqueous solutions show a vapour pressure of 39.39 hPa at 20°C (see supporting study: BASF, 2010). Since the vapour pressure of H4EDTA is with respect to (NH4)4EDTA neglibly low, the determined vapour pressure represents a vapour consisting of solely H2O and NH3. Due to the fact that a 50 w% solution (NH4)3HEDTA exerts a neglibly low partial pressure of ammonia at 20°C, we conclude that max 1 eq NH3 is released and the vapour in equilibrium with 50% (NH4)4EDTA is at most the vapour in equilibrium with a 2.4* w% solution NH3 in H2O (50 w% * M (NH3) / M (NH4EDTA) = 50 w% * 17 / 380 = 2.4 w%).

For the vapour pressure of tetraammonium ethylenediaminetetraacetate, read across to the free editic acid was done (see key study). The vapour pressure determined for the acid form of EDTA represents also a worst case (highest) value for its ammonium salts as it is belived that only the free acid can evaporate. In conclusion the value determined for the free acid will also be used for the exposure calculations of the ammonium salts in the chemical safety report.