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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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


Data waiving: Sodium chlorite is not expected to hydrolyse under abiotic test conditions in ultrapure water.

The performance of a Guideline study such as OECD 111, without modifications of the study design to use natural water or artificially increase organic matter or suspended solids, will not provide any information that is relevant to the behaviour of sodium chlorite in the environment, and is, therefore, scientifically unjustified.

Phototransformation in water:


Irradiation of sodium chlorite solutions indicated a photodegradation half-life of about 30 minutes with a steady increase in pH (pH 8 to 12.6) and major products identified as hydroxide, chlorine dioxide and chloride with chlorate and hypochlorite as minor products and trace amounts of chlorine.


The results obtained show that the pH and the initial concentration of sodium chlorite have no significant effect on the rate of photodecomposition of chlorite. These results also indicate that the radiation dose (9000 j/m2) needed to produce a 50% reduction in chlorite concentration suggests that the doses (200-250 j/m2) used for drinking water disinfection would not result in a significant reduction in chlorite concentrations.


The rate of photodecomposition of sodium chlorite was studied over a pH range of 4-10 and at unbuffered conditions. Distribution of major products was not affected by pH; rates of reaction and chlorine dioxide formation were maximum at pH 6. Quantum yields were measured for both photodecomposition of chlorine dioxide and sodium chlorite. For the former reaction, the values were 0.44 at 253.7 nm and 1.4 at 300 nm. For the latter reaction, the values at 253.7 nm ranged from 0.72 to 1.53, depending upon pH. Corresponding quantum yields for formation of chlorine dioxide ranged from 0.43 to 0.94, depending upon pH.

Additional information