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Physical & Chemical properties

Water solubility

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Description of key information

Read-across of aqueous solubility measurements on iron sinters (Jackson et al, 2010) and of solubility data for pure di-iron trioxide was used to estimate the solubility of  iron pellets. This approach is justified on the basis that iron pellets consist principally of di-iron trioxide (>90%) so the solubility of iron will be the same as for sinter and di-iron trioxide, where measured solubilities of <0.05 μg/l and <1 μg/l were reported.
Mathematical modelling studies (Thompson, 2010; ETAP, 2010) also confirm the extremely low solubilities of iron oxides.

Key value for chemical safety assessment

Water solubility:
0.05 µg/L
at the temperature of:
25 °C

Additional information

Iron pellets consist principally of di-iron trioxide (Fe2O3), with small amounts of non-ferruginous phases such as silicates and aluminates. The overall solubility of iron pellets is therefore largely determined by the solubility of di-iron trioxide. Thermodynamic calculations (Thompson, 2010) and experimental measurements (Currenta, 2009) show that iron oxides are insoluble with < 1 μg/l of iron dissolved from di-iron trioxide. These data are confirmed by the study of Jackson et al on the solubility of iron sinter, in which the solubility of iron was determined to be < 0.05 μg/l. The results demonstrate that the aqueous solubility of iron sinter is so low that it does not become bioavailable to human health or ecosystems, and therefore the same conclusions can be drawn for iron pellets.