Registration Dossier
Registration Dossier
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EC number: 223-888-3 | CAS number: 4109-96-0
Water solubility
Administrative data
Link to relevant study record(s)
Description of key information
Water solubility (substance): Not relevant
Water solubility (monosilicic acid): approximately 100 - 150 mg/l SiO2/l with condensation occurring at higher concentrations.
Key value for chemical safety assessment
- Water solubility:
- 150 mg/L
Additional information
The requirement to test the substance for water solubility is waived because in contact with water the substance rapidly (violently) hydrolyses to form initially silanediol and hydrochloric acid. With further reaction of the Si-H bonds and loss of hydrogen, monosilicic acid is formed.
At concentrations >100 -150 mg/l as SiO2 according to published sources, monomeric silanediol/monosilicic acid condense rapidly into a highly cross-linked network (gel) or colloidal particles of polysilicic acid. The condensation rate is dependent on temperature, concentration, and acidity or alkalinity of the system. A dynamic equilibrium is established between monomer, oligomers and insoluble amorphous polysilicic acid.
A water solubility of 1E+06 mg/l at 20°C for silanediol and monosilicic acid estimated using a QSAR estimation method shows that the substance is very hydrophilic. The method has not been validated for inorganic substances and does not take into account the condensation reaction.
Further details are given in a supporting report (PFA 2015ao) attached in Section 13 of the IUCLID dataset. PFA, 2015ao, Peter Fisk Associates, The aquatic chemistry of inorganic silicic acid generators, PFA.404.001.001
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