Registration Dossier
Registration Dossier
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EC number: 237-041-0 | CAS number: 13596-23-1
Water solubility
Administrative data
Link to relevant study record(s)
Description of key information
Water solubility [ octachlorotrisilane]: not relevant due to very rapid hydrolysis
Water solubility [octahydroxytrisilane]: 1.0E+06 mg/L at 20°C
Water solubility [monosilicic acid]: 1.0E+06 mg/L at 20°C
Key value for chemical safety assessment
Additional information
In accordance with Column 2 of REACH Annex VII, the water solubility study does not need to be conducted as the substance has a hydrolytic half-life less than 12 hours at pH 4, 7 and 9.
Octachlorotrisilane reacts rapidly with water, generating octahydroxytrisilane and hydrochloric acid. The Si-Si bonds may also react to produce monosilicic acid. At concentrations above about 100-150 mg/l (measured as SiO2equivalents), condensation products of monosilicic acid can also form. At concentrations >100-150 mg/l of SiO2, monomeric monosilicic acid condenses into colloidal particles of polysilicic acid (silica sol) or a highly cross-linked network (silica gel). The condensation rate is dependent on temperature, concentration, and acidity/alkalinity (as in the pH) of the system. A dynamic equilibrium is established between monomeric monosilicic acid, oligomers and insoluble amorphous polysilicic acid. Octahydroxytrisilane is also likely to form condensation products (polyhydroxy-polysilanes) at similar concentrations (in terms of SiO2 equivalents).
A water solubility of 1.0E+06 mg/L was obtained for octahydroxytrisilane and monosilicic acid using an appropriate calculation method. The method has not been validated for inorganic substances and does not take into account the condensation reaction.
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