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Environmental fate & pathways

Hydrolysis

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According to REACH Annex XI, a hydrolysis study is scientifically not necessary.
The study investigating the water solubility of the substance provides evidence that the substance dissociates immediately in zinc chloride, the zinc hexacyanocobaltate complex as well as tertiary butyl alcohol plus polypropylene glycol when dissolved in water. Therefore, the hydrolytical stability of the substance is preferably described by the properties of the individual components. Zink chloride is known to completely dissociate in water, whereas after addition of alkaline lye zink hydroxide will precipitate, which will be resolved in the presence of a surplus of the alkaline lye forming zincates (Römpp Chemical Encyclopedia, Thieme Chemistry, 2011). The specification on zinc in the environment strongly depends on the prevailing environmental conditions (e.g. pH).
In view of the chemical nature of zinc hexacyanocobaltate, a hydrolysis in the conventional sense is not assumed. Nevertheless, dissociation might occur rather than hydrolysis.
Polypropylene glycol is classified as readily biodegradable and thus assumed to undergo a rapid degradation in the environment. The investigation of hydrolysis is thus not required.
In the absence of hydrolysable functional groups, tertiary butyl alcohol is hydrolytically stable under environmental conditions. Only at pH values above 11, the hydroxyl group will be deprotonated.
Concluding, the substance was shown not to hydrolyse in water in a conventional sense. The substance effectively dissociated and the various components were released to a different extent when the substance was exposed to water. Based on the available information, the stability of the substance in the aquatic environment is sufficiently described. A new study according to OECD 111 would not result in additional information.

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