Registration Dossier
Registration Dossier
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EC number: 285-349-9 | CAS number: 85085-18-3
Endpoint summary
Administrative data
Description of key information
Additional information
This substance is stable under the methods of test devised to demonstrate dissociation and hydrolysis.
This substance is an inorganic layered silicate structure with a unit cell of the following composition Na0.7[Mg5.3Li0.7Si8O20(OH)0.0F4.0].
The material is non-biodegradable, retaining its clay structure in the environment. At normal water course pH’s this material is stable and insoluble. It does not dissolve in water but disperses to form a slightly cloudy sol so the usual methods to determine water solubility do not work because it appears by observation that total dissolution has taken place whereas in reality the structure has remained unchanged but simply dispersed to be invisible to the naked eye. To demonstrate whether any solubility to the component ions takes place, a dialysis method was devised to determine solubilised ions present. Based on the structure above, lithium and magnesium ions were determined to be key unique identifiers of whether the structure under defined conditions dissociates in water (sodium and fluoride whilst present in the structure are also found in process impurities external to the layer structure). The natural pH of this substance in water at a concentration of 0.5% by weight is 8.4. At that pH, no free lithium or magnesium ions are found in solution and only low level concentration of sodium and fluoride ions which are present from dissociation of impurities from the manufacturing process.
To demonstrate hydrolysis at lower pH, the dialysis test was carried out by adjusting the dispersion to pH1, pH4 and pH7 and measuring Li, Mg, ions that pass through the membrane into demineralised water on the other side of the membrane. At pH4, and pH7 no Li and Mg ions were measured thus concluding that hydrolysis does not take place at the range of pH covered in the prescribed OECD method (4-9).
The material does not exhibit and phototransformations in any medium.
Laponite Type 1 is a stable material under normal environmental conditions.
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