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Water solubility

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Description of key information

Based on measured maximum zinc concentrations ranging from  < 1 µg/L to 176 µg/L, the water solubility of zinc bis[12-hydroxyoctadecanoate]  ranges from < 0.01 to 1.69 mg/L depending on test conditions.
In the key study on water solubility according to OECD guideline 105 and up to and including 23 days extended period of steering, water solubility was 1692 ± 180 µg/L at 20.0°C ± 1.0°C based on the measured zinc concentrations of 176.0 ± 18.7 µg/L and a zinc content of the test item of 10.4%.

Key value for chemical safety assessment

Additional information

The solubility of zinc bis[12-hydroxyoctadecanoate] in the key study performed according to OECD guideline 105 and EU method A.6 (2008) was 1.69 mg/L. This value is based on the measured zinc concentrations of 176 µg/L and zinc content of the test item of 10.4% and assumes acomplete dissolution of zinc bis [12 -hydroxyoctadecanoate].

However, since zinc bis[12-hydroxyoctadecanoate] concentration has not been experimentally confirmed, it may be more appropriate to express the solubility of zinc bis[12-hydroxyoctadecanoate] in measured dissolved zinc concentrations (176 µg/L Zn).

In an additional reliable supporting study water solubility was below the limit of detection (0.01 mg zinc bis[12-hydroxyoctadecanoate]/L, respectively 0.001 mg zinc/L).

For Fatty acids, C16 -18, zinc salts (CAS 91051 -01 -3), a structural analogue fatty acid zinc salt to zinc bis[12-hydroxyoctadecanoate] (CAS 35674 -68 -1) with comparable chain length and zinc content, it was also demonstrated, that the solubility depends on exposure time, but also on several further factors, including loading an solution matrix (pH, ionic strength, other salts). In water, solubility of Fatty acids, C16 -18, zinc salts (CAS 91051 -01 -3) ranges from 0.3 to 1.8 mg/L depending on test conditions. However, these calculations assume a 1:1 dissolution of zinc and a zinc content of ca. 10%. However, as stearate concentrations have not been experimentally confirmed, it may be more appropriate to express the solubility of Fatty acids, C16-18, zinc salts in resulting dissolved zinc concentrations (0.03 to 0.18 mg/L).

In more complex media simulating environmental solutions, solubility resulted in 0.02 to 0.9 mg/L dissolved zinc depending on test conditions. The following dissolved zinc concentrations have been measured in three different studies (most relevant for the classification of Fatty acids, C16-18, zinc salts are the data obtained by Schäfers (2010) in transformation dissolution studies (guideline conform and under GLP) for 7 and 28 days with loadings of 1, 10 and 100 mg/L):

Schäfers (2010)

ISO 6341 media at pH 8:

Loading 1 mg/L:

-after 7 days: 19 µg Zn/L

-after 28 days: 29 µg Zn/L

Loading 10 mg/L:

-after 7 days: 90 µg Zn/L

Loading 100 mg/L:

-after 7 days: 369 µg Zn/L

Bouwman (2003)

ISO 6341 at pH 6:

Loading 100 mg/L:

-after 2 days: 208 µg Zn/L

ISO 6341 at pH 8

Loading 100 mg/L:

-after 2 days: 475 µg Zn/L

M7 at pH 6:

Loading 100 mg/L:

-after 2 days: 325 µg Zn/L

M7 at pH 8

Loading 100 mg/L:

-after 2 days: 900 µg Zn/L

Bowmer (2001)

Modified ISO 6341 at pH 6.75:

Loading 10 mg/L:

-after 4 days: 241 µg Zn/L

Modified ISO 6341 at pH 6.75

Loading 100 mg/L:

-after 4 days: 431 µg Zn/L)

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