Registration Dossier
Registration Dossier
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EC number: 304-802-4 | CAS number: 94279-56-8
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
Not possible to measure
Key value for chemical safety assessment
Additional information
The substance reacts with water. The water soluble reaction product is a multi-constituent substance:
Reaction mass of disodium metasilicate and sodium hydroxide (EC 910-245-3)
Sodium hydroxide:
In water (including soil or sediment pore water), NaOH is present as the sodium ion (Na+) and hydroxyl ion (OH-), as solid NaOH rapidly dissolves and subsequently dissociates in water. If emitted to soil, sorption to soil particles will be negligible. Depending on the buffer capacity of the soil, OH- will be neutralised in the soil pore water or the pH may increase.
Disodium Metasilicate:
The basic consideration is that silica dissolves according to: SiO2 + H2O = Si(OH)4. At low concentrations most species are present as monomers, at higher concentrations polymerisation will occur. Most soluble silicates are in the form: (M2O)x . (SiO2)y . nH2O where M = alkali metal, predominantly Na, but also K. The molar ratio ranges between 0.5 - 4, most commonly 3.3. Stability depends to a large extent on pH, above pH 10.6 the solutions are chemically stable. The increase of ionic strength accelerates nucleation and deposition and decreases the SiO2 solubility. Coating of surfaces by organic matter may hamper dissolution, but at the same time Si(OH)4 may form complexes with organic matter, a process which favours dissolution.
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