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Water solubility

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Description of key information

The water solubility of Ca-/Mg-salt of Fumarated Tall Oil Rosin was determined at 20°C according to OECD TG 105 using the flask method.
At an initial weight of 10 g /L and 0.1 g/L, a water solubility of 0.154 to 0.442 g/L test item and < 0.0027 g/L test item, respectively was observed.

Key value for chemical safety assessment

Water solubility:
442 mg/L
at the temperature of:
20 °C

Additional information

As the test item is a UVCB substance, the test design had to be adapted. The flask method was chosen to determine the water solubility of Ca/Mg-salt of fumarated Tall Oil Rosin, as the elution method is not suitable for UVCB substances.

For a complex substance the water solubility fraction strongly depends on the amount of test substance added. Therefore, two loading rates (0.1 g/L and 10 g/L) were tested resulting in a significant higher water solubilty at an initial weighing of 10 g/L compared to concentrations found at initial concentrations of 0.1 g/L. As the substance consists of components with a low as well as a high water solubility, higher loading rates might thus result in the dissolution of higher portions of soluble components. Experiments were evaluated on the basis of the total organic carbon (TOC) content of the aqueous phase (sum parameter), as the quantification based on individual components is not feasible.

Normally, the flasks are stirred up to 72 h to achieve equilibrium between the dissolved and undissolved fraction shown by a constant aqueous concentration throughout the test period. This could not be observed as the concentration found in the water phase decreased after 48 h.

To determine aqueous concentrations after distinct periods of stirring (24 h, 48 h and 72 h), individual flasks were prepared. As the test item was coarse grained having a heterogeneous particle size distribution, each flask might contain grains of different sizes. The dissolution behavior might thus be influenced by the surface area of the pieces included explaining the decreasing aqueous concentration after 48 h.

Concluding, the variable concentrations observed result from the complex substance composition (presence of good soluble components besides poorly soluble ones) as well as the heterogeneous particle size distribution of the sample. Even so, the study was scored as valid for assessment providing information about the order of magnitude in which the substance will be dissolved in an aqueous medium.

It is assumed that the highest value reported represents the worst case, this was taken as key value.