Registration Dossier
Registration Dossier
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 241-034-8 | CAS number: 16961-83-4
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
At environmental pH, the dissociation of hexafluorosilicate to fluoride is essentially 100%.
Key value for chemical safety assessment
Additional information
Overview of hydrolysis
Hexafluorosilic acid is manufactured as a concentrated solution that contains a significant amount of hydrofluoric acid (HF) to prevent the dissociation and hydrolysis of hexafluorosilicic acid. In an aqueous environment, hexafluorosilic acid dissociates with the formation of hydrogen fluoride:
H2SiF6→ 2HF + SiF4
and subsequent hydrolysis of silicon tetrafluoride:
SiF4+ H2O → 4HF + Si(OH)4
The resulting hydrogen fluoride will dissociate to from hydrogen and fluoride ions:
HF → H++ F-
The behaviour of soluble silicates is complex. The net reaction given below:
H2SiF6+ H2O → 6HF + Si(OH)4
may actually cover a number of reactions:
H2SiF6+ 6 OH-→6F-+ Si(OH)4+ 2 H2O
H2SiF6+ 8 OH-→6F-+ SiO2(OH)22-+ 4 H2O
H2SiF6+ 8 OH-→6F-+ SiO32- +5 H2O
The overall rate and equilibrium constant of the overall reaction will be influenced by pH and concentration, but at typical environmental pH, the dissociation and hydrolysis of hexafluorosilicate to fluoride is essentially 100%.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
