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Physical & Chemical properties

Water solubility

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Description of key information

Initially very soluble (>>10 g/L), rapid transformation/speciation in environmental waters and body fluids
Initial solubilities
FeCl3: Anhydrous 744 g/L; Hexahydrate 919 g/L

Key value for chemical safety assessment

Additional information

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 salts are not stable and undergo fast hydrolysis (DT50 < 12 h) in water, particularly if oxygen is present and the pH is in the common environmental ranges. Nonetheless a number of generally high initial water solubilities are published, which are reported in the following paragraphs. Comparably aqueous solutions are initially (i.e. before transformation/speciation) unlimitedly miscible with water and water solubility is not a relevant endpoint for them, as they are unlimitedly miscible with water.

Ferric chloride (FeCl3)

The best available value is 744 g/L (for the anhydrous salt) at 0 ºC (Lide 2003). This is supported by a number of values reported in a range of sources, which report 477 to 920 g/L. The value 919 g/L at 20 ºC has been reported for the hexahydrate (Weast 1977), while less reliable sources report a range of 470 to 1535 g. The anhydrous salt and hydrated forms have thus remarkably high initial solubility in water.

Table: Initial water solubilities [g/L] of the registered category member salt forms


Anhydrous form

Solid hydrate form

Aqueous solution

Ferric chloride, FeCl3

744 at 0 °C

Hexahydrate (CAS 10025-77-1): 919 at 20 °C

Unlimited miscibility

Ferric and ferrous kations

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)


Ferrous iron (II)

Ferric iron (III)

[mg Fe/L]


[mg Fe/L]



























In conclusion the limit of the ferric iron kation solubility is even at significantly acidified conditions is of the order of ng Fe(III)/L.

  • Lide DR ed (2003). CRC Handbook of Chemistry and Physics. 84th edn. ISBN 0-8493-0484-9. Boca Raton, Florida, U.S.A. CRC Press. 2616 p.
  • 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.
  • Weast RC ed (1977). CRC Handbook of Chemistry and Physics. 58th edn (1977-1978) ISBN 0-8493-0458-X. Boca Raton, FL, U.S.A. CRC Press. 2348 p.