Registration Dossier

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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Trichlorosilane hydrolyses very rapidly (half-life approximately 5 seconds at 25°C) to form hydrogen chloride and silanetriol. Further hydrolysis of silanetriol then occurs rapidly to form monosilicic acid [Si(OH)4] and hydrogen. Both silanetriol and silicic acid exist only in dilute aqueous solutions and readily condense at concentrations above 100 -150 mg/L as SiO2 to give dynamic equilibrium between monomer, oligomers and insoluble amorphous polysilicic acid.

These hydrolysis products are inorganic substances which enter natural biogeochemical cycles. The ultimate hydrolysis product, silicic acid, is a naturally occurring substance which is not harmful to aquatic organisms and will be incorporated into solid inorganic matrices such as silica. In addition, silicic acid is known to be the major bioavailable form of silica for aquatic organisms and plays an important role in the biogeochemical cycle of silicon. Most living organisms contain at least trace quantities of silicon. For some species silicon is an essential element taken up actively. For example, diatoms, radiolarians, flagellates, sponges and gastropods all have silicate skeletal structures. The potential releases of inorganic silicon resulting from use of trichlorosilane are negligible compared to the natural flux of silica in the environment. It is not appropriate to calculate Predicted Environmental Concentrations (PECs) for monosilicic acid. Refer to Section 9.0 of the CSR.

The properties of hydrogen chloride are well-characterised, and its effects are limited to those that result from changes to pH in unbuffered media.

Additional information