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EC number: 233-162-8
CAS number: 10049-04-4
The substance Chlorine-dioxide (EC 233-162-8, CAS 10049-04-4, ClO2) is an unstable oxidizing gas only generated in-situ and used at less than 2%w/w in water. Water is acting as a stabilizing agent against explosive/oxidizing properties. The highest possible recognized concentration which guarantees safe handling of the substance is 2-3%w/w in aqueous solution at 25 ° C under a reduced pressure of 4600 Pa.
Therefore the substance registered in this dossier is the solution generated in-situ at less than 2%w/w in water. At this concentration, some of the physico-chemical properties of the registered substance are anticipated to be similar to the solvent.
Other physico-chemical properties are anticipated from available litterature data on the gaseous form of the substance. Note also that solubility is correlated to the pressure over the solution (and temperature), and in certain conditions, off-gassing may occur. Despite the solution should not be classified as hazardous as such, this phenomenon may lead to violent reaction as the gas is oxidising.
For that reason, available data on the pure gaseous substance and on the Solution generated in-situ at less than 2%w/w in water (as registered) were discussed in this dossier and summarized as follows:
Solution of chlorine dioxine generated in-situ at less than 2% in water
(not registered as such, due to unstability)
Physical state at 20°C and 1013 hPa
with a chlorine-like odour, expected to be perceptible, if not in closed systems.
green-yellow to orange-red depending on concentration with chlorine-like pungent odour. (literature data)
Melting point / freezing point
<= 0°C (close to the MP of water)
(waiving : expert statement)
-59°C at reduced pressure (10 mm Hg = 1333 Pa). (exp. Data & literature data)
<= 100°C (close to the BP of water)
11°C at atm. P (1013 hPa)
(exp. Data & literature data)
1 (close to the relative density of water)
theoretical relative density : 1.008
relative density : at 0°C (liquid) - 1.64
Particle size distribution (Granulometry)
Vapour pressure is a function of temperature and
Calculated ClO2 partial pressure at 20°C over 20 g/L = 22900 Pa
At 0°C, the calculated value between 65.3 and 68.1 kPa.
Waiving (inorganic substance)
-3.22 (QSAR : Estimated value)
The substance as registered should be fully soluble in water but Water solubility is a function of temperature and
partial pressure (off-gassing).
(waiving : expert statement - see also comment on pure ClO2)
Water solubility is a function of temperature and
Concentrations up to 60 g/L or more can be reached (parameters not specified), but unstable. Typically, 3 g/L at 25°C and 4600 Pa seems to be recognised as stable and safe.
Waiving (chemical structure)
Waiving (gaseous inorganic substance)
Waiving (release the gas if heated - EUH018 proposed)
Waiving (explosive substance)
Waiving (This endpoint does not apply to the substance as registered (aqueous solution generated in-situ), as liquid.)
(waiving: expert statement)
The gas has a Harmonised Classification as Oxidising, therefore it does not need to be classified in any other hazard class.
Chlorine dioxide gas: LEL = 4 (sparks) - 10 (any source of ignition) %v/v in air.
For chlorine dioxide in aqueous solution, no physical hazard is established in the harmonised entry.
However, based on the potential hazard if off-gassing, the EUH018 phrase is proposed.
(literature data / expert statement)
The gas is well-known to be sensitive to various sources of ignition (heat, light, shock, and in particular sparks), and is characterised by an induction period.
However, the gas has a Harmonised Classification as Oxidising, therefore it does not need to be classified in any other hazard class.
(literature data provided).
Waiving : not considered to be oxidising, but potential hazard if off-gassing.
(waiving: expert statement & Literature data)
CLH : Ox. Gas 1, H270: May cause or intensify fire; oxidiser.
Waiving (no ionization anticipated)
ca 1 mPa.s at 20°C (close to the viscosity of pure water)
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.
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