Registration Dossier
Registration Dossier
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EC number: 940-441-4 | CAS number: -
Water solubility
Administrative data
Link to relevant study record(s)
Description of key information
Initially slightly soluble, but hydrolytically unstable; limit of the ferric iron kation solubility in the order of ng Fe(III)/L
Key value for chemical safety assessment
Additional information
- OECD Organisation for Economic Co-operation and Development (2007). SIDS Initial Assessment Report for SIAM 24. Chemical Category: Iron Salts. Self-published, Paris, France, 17-20 April. 138 p.
Testing for this endpoint has been waived in accordance with column 2 restrictions. All soluble iron salts dissociate in aqueous media to the respective anions and kations, and are then subject to further change of oxidation and speciated state according to the conditions. Thus the salt is not stable and undergoes fast hydrolysis (DT50 < 12 h) in water at pH in the common environmental ranges.
Ferric and Ferrous kations
However initially a ferric salt, redox processes occur naturally and cause equilibrium of ferrous and ferric kations depending on the conditions. In presence of oxygen ferrous kations are readily oxidized to ferric kations, which are thus more important for the environmental assessment of aerobic waters.
The following Table below shows the maximum dissolved concentration of the iron kations in pure water as it depends upon pH (see section on Hydrolysis).
Table: Calculated maximum solubility of iron in solution at 20 °C depending on pH (OECD 2007, table 13, p 33)
pH |
Ferrous kation; iron (II) |
Ferric kation; iron (III) |
||
[mg Fe/L] |
[mmol Fe/L] |
[mg Fe/L] |
[mmol Fe/L] |
|
4 |
>1E+06 |
>1.8E+04 |
6.16E-02 |
1.1E-03 |
5 |
>1E+06 |
>1.8E+04 |
6.16E-05 |
1.1E-06 |
6 |
>1E+06 |
>1.8E+04 |
6.16E-08 |
1.1E-09 |
7 |
89'600 |
1'600 |
6.16E-11 |
1.1E-12 |
8 |
896 |
16 |
6.16E-14 |
1.1E-15 |
In conclusion the limit of the ferric iron kation solubility is even at significantly acidified conditions in the order of ng Fe(III)/L
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