Sodium hypochlorite

Endpoint summary

Additional information

General remark:

Sodium hypochlorite does not exist as a pure salt at room temperature. It is produced and handled in form of aqueous solutions only. In general, sodium hypochlorite solutions contain between 12 to 16 % (w/w) available chlorine. However concentrations up to 24 % available chlorine can be produced mainly for industrial use. Owing to these facts, this chapter is mainly based on data of recently performed studies on a 24 % available chlorine solution (as this is the highest technically feasible concentration) and on literature data, which also addresses those physical-chemical parameters which are meaningful for sodium hypochlorite.

Summary of physical and chemical properties:

Appearance:	Yellow, limpid liquid with a chlorinated odour (Tieche, A., 2007)
Melting point.	-28.9 +/- 0.5 °C (purity: 24.3 % available chlorine) (Tieche, A., 2007)
Boiling point:	As sodium hypochlorite solution is an aqueous mixture of an inorganic salt, water will evaporate when heating the solution. After removal of water, white crystals are observed on the bottom of the test and boiling point cannot be determined (Tieche, A., 2007).
Relative density:	D (21.2°C/4 °C) = 1.300 +/-0.001 (purity: 24.3 % available chlorine) (Tieche, A., 2007)
Granulometry	In accordance with colum 2 of REACH Annex VII, the particle size determination test (required in section 7.14) does not need to be conducted as sodium hypochlorite is marketed or used in a non solid or granular form.
Vapour pressure:	negligible
Henry’s law constant:	negligible
Solubility in water:	Sodium hypochlorite is completely miscible in water.
Dissociation constant:	K = 2.9 x 10^-8(at 25 °C); pK = 7.53 (Pinto, G., 2003).
Partition coefficient: n-octanol/water, log POW	The log Pow of NaOCl was calculated to be: log Pow : - 3.42 The value was calculated using KOWWIN v1.67 (Anonymous, 2007).
Thermal stability:	Half life of a 10 % av Cl solution at different temperatures: 15 °C: 800 days; 25°C: 220 days; 60 °C: 3.5 days; 100 °C: 0.079 day and for a 5 % solution: 15 °C: 5000 days; 25°C: 790 days 60 °C: 13.5 days; 100 °C: 0.25 day. Relevant breakdown products are chlorate and chloride (White, G., 1972).
Auto flammability	In accordance with column 2 of REACH annex VII, the study does not need to be conducted for liquids non flammable in air. The sodium hypochlorite solution has no flash point up to 111°C, temperature at which the product starts to decompose. Thus the sodium hypochlorite solution is non flammable in air and the auto-flammability test is not required.
Flammability	For a liquid such as the aqueous solution of sodium hypochlorite, the primary value for ease of ignition is the flash point. No flash point was observed up to 111°C. Thus the substance is not regarded as flammable. A test on flammability in contact with water does not need to be conducted as the substance is marketed and used in aqueous solution and experience in handling and use gives no indications that the substance reacts with water. A test on pyrophoric properties does not need to be conducted as experience in handling and use gives no indications that the substance ignites or reacts with air.
Flash point:	No flash point was observed up to 111°C. No main test was performed. (purity: 24.3 % available chlorine) (Ferron, N., 2007)
Surface tension:	82.4 mN/m +/-0.8 mN/m at 20.2-20.3°C (Ferron, N., 2007)
Explosive properties:	In accordance with column 2 of REACH Annex VII, explosive properties (required in section 7.11) does not need to be conducted as there are no chemical groups associated with explosive properties present in sodium hypochlorite (refer to Guidance on information requirements and chemical safety assessment, Chapter R.7a).
Oxidising properties:	The mean pressure rise time obtained with the mixture test item / cellulose was slower than the mean pressure rise time obtained with the mixture reference item / cellulose thus sodium hypochlorite 100 does not have oxidising properties. As testing was triggered by the presence of hypochlorite ions, the lack of oxidising propertie in sodium hypochlorite 100 indicates that solutions with a lower sodium hypochlorite concentration will not have oxidising properties.
Stability in organic solvents and identity of relevant degradation products	In accordance with column 2 of REACH Annex IX, Stability in organic solvents and identity of relevant degradation products (required in section 7.15) does not need to be conducted as Sodium hypochlorite is inorganic.
pH	The pH value of sodium hypochlorite solutions is alkaline. The pH value of a 5 % sodium hypochlorite solution was determined to be pH = 12.52 at 19.1 °C for the pure test item pH = 10.30 at 21.3 °C for a 1 % (m/v) solution (Ferron, 2007).
Viscosity	Viscosity:6.2 – 6.6 mPa.s (at 20°C ± 0.2°C) Viscosity:4.0 mPa.s for a rotation of 200 rpm (at 40°C ± 0.2°C) For lower purities of sodium hypochlorite (5 % and 14 %) also lower viscosity values were measured (Tieche, A., 2007).
Reactivity towards container material:	Common metals should never be used for the storage and handling of sodium hypochlorite.Suitable materials are: PVDF,PTFEE, PVC, CPVC (NF EN 901, 1999).