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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Administrative data

Description of key information

This substance is a multi-constituent substance consisting of sodium hydroxide (215-185-5, 1310-73-2) and disodium metasilicate (229-912-9, 6834-92-0). It is the by-product of a reaction between zircon (EC no 239-019-6) and sodium hydroxide; after hydrolysis, this substance is the water-soluble fraction.  The substance has a pH of >13 due to the presence of significant amounts of residual sodium hydroxide.  The substance as produced would be highly corrosive to skin due to the sodium hydroxide; testing would not be required to demonstrate this is the properties of sodium hydroxide are well-known.  In vivo testing of the substance would be inappropriate on animal welfare grounds, and such testing for substances where the pH is >11 is prohibited.  The substance is classified based on this as skin corrosion/irritation, category 1A (H314), i.e. corrosive.  Therefore it is expected that this substance would also be irritating to the respiratory tract.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion
Endpoint conclusion:
no study available

Eye irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Sodium Hydroxide: Source - the sodium hydroxide summary risk assessment report JRC EC 2008

NaOH is a corrosive substance. A NaOH concentration of 2% is taken forward to the risk characterisation as concentration limit for corrosivity. Based on human data concentrations of 0.5–4% were irritating for the skin. No human data on local effects to the eyes was available. The available animal data on eye irritation revealed small differences in eye irritation levels. The non-irritant level was 0.2-1.0%, while the corrosive concentration was 1.2%. The concentration limits for irritation which are taken forward to the risk characterisation are 0.5-2% NaOH.

Based on a study among workers, concentrations up to 1.0 mg/m3 are not considered adverse with regard to respiratory tract irritation.


Justification for selection of skin irritation / corrosion endpoint:
This substance is a multi-constituent substance consisting of sodium hydroxide (215-185-5, 1310-73-2) and disodium metasilicate (229-912-9, 6834-92-0). It is the by-product of a reaction between zircon (EC no 239-019-6) and sodium hydroxide; after hydrolysis, this substance is the water-soluble fraction. The substance has a pH of >13 due to the presence of significant amounts of sodium hydroxide. The substance as produced would be highly corrosive to skin due to the sodium hydroxide; testing would not be required to demonstrate this is the properties of sodium hydroxide are well-known. In vivo testing of the substance would be inappropriate on animal welfare grounds, and such testing for substances where the pH is >11 is prohibited. The substance is classified based on this as skin corrosion/irritation, category 1A (H314), i.e. corrosive. Disodium metasilicate (229-912-9) has been tested for skin irritancy; this would not contribute at all to the corrosiveness due to the sodium hydroxide present in this substance.

Justification for selection of eye irritation endpoint:
This substance is a multi-constituent substance consisting of sodium hydroxide (215-185-5, 1310-73-2) and disodium metasilicate (229-912-9, 6834-92-0). It is the by-product of a reaction between zircon (EC no 239-019-6) and sodium hydroxide; after hydrolysis, this substance is the water-soluble fraction. The substance has a pH of >13 due to the presence of significant amounts of residual sodium hydroxide. The substance as produced would be highly corrosive to skin due to the sodium hydroxide; testing would not be required to demonstrate this is the properties of sodium hydroxide are well-known. In vivo testing of the substance would be inappropriate on animal welfare grounds, and such testing for substances where the pH is >11 is prohibited. The substance is classified based on this as skin corrosion/irritation, category 1A (H314), i.e. corrosive. Disodium metasilicate (229-912-9) has been tested for eye irritancy; this would not contribute at all to the corrosiveness due to the sodium hydroxide present in this substance.

Effects on skin irritation/corrosion: corrosive

Effects on eye irritation: corrosive

Effects on respiratory irritation: irritating

Justification for classification or non-classification