ENTRY 6

Hydrates of a substance or hydrated ions, formed by association of a substance with water, provided that the substance has been registered by the manufacturer or importer using this exemption. 

Hydrates of a substance are characterised by the fact that water molecules are linked, in particular by hydrogen bonds, to other molecules or ions of the substance. A substance that does not contain any water is referred to as anhydrous. Solid hydrates contain water of crystallization in a stoichiometric ratio, an example of which would be NiSO4:7H2O. The chemical formula expresses the fact that one molecule of NiSO4 can crystallise with seven molecules of water. 

It is important to note:

The manufacturer or importer relying on this exemption registers the substance in the anhydrous form. It is recommended to make reference to the hydrated form(s) in the registration dossier. 

Companies changing the hydration state of a substance (i.e. changes the number of water molecules associated with the substance), are considered as downstream users provided that the anhydrous form of the substance has already been registered by the manufacturer or importer up the supply chain. These hydration or drying processes should be covered in any applicable exposure scenario in the registration by the manufacturer or importer. 

A registrant who wants to make use of the exemption under this entry needs to add up the quantities of the anhydrous form and the different hydrated forms in his technical dossier (but excluding the water which is attached to the parent molecule).