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Physical & Chemical properties

Water solubility

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Description of key information

The solubility of the pigment is <0.8% (w/w) at 1 mg loading and pH 6 after 28 days. After 7 days at a higher loading of 100 mg the solubility of the pigment is <0.05% (w/w) at pH 6.

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Additional information

The water solubility of zinc iron chromite brown spinel was measured according to the method OECD test series No. 29 (Guidance document on transformation/dissolution of metals and metal compounds in aqueous media). The transformation/dissolution of the pigment resulted in the following dissolved concentrations:

Full test 7 days at 1 mg/L and pH 6: < 0.9 µg/L Cr, < 0.8 µg/L Ni, < LoD Fe and < 2.9 µg/L Zn

Full test 28 days at 1 mg/L and pH 6: <1.2 µg/L Cr, < 1.1 µg/L Ni, < 0.23 µg/L Fe and < 4.5 µg/L Zn

Full test 7 days at100 mg/L and pH 6: 0.87 ± 0.14 μg/L Cr, <LOD/LOQ Fe, 5.58 ± 0.48 μg/L Ni, 37.1 ± 3.65 μg/L Zn

Full test 7 days at 100 mg/L loading and pH 8: 0.51 ± 0.02 μg/L Cr, <LOD Fe, 1.51 ± 0.23 μg/L Ni, 0.68 μg/L Zn

As dissolved Cr, Ni, Fe and Zn concentrations were below 4.5 µg/L respectively, at a loading of 1 mg/L, referring to a total solubility of < 0.8 %, the pigment can be considered environmentally inert. At loadings of 100 mg at pH values 6 and 8 after 7 days, the highest dissolution was observed at pH 6 with a total dissolution of <45 µg/L (Cr, Ni, Fe and Zn).