Lepidocrocite solubility products

Ferrihydrite has indeed been found in association with magnetite in Magnetospirillum magnetotacticum (Frankel et ah, 1983). It seems essential that the cell solution is sufficiently buffered to maintain a neutral pH and thus ensure that the solubility product of magnetite is always exceeded. This is a reaction which easily takes place in a purely inorganic system at ambient temperature (see chap. 14). Lepidocrocite has also been suggested as a magnetite precursor (Abe et al. 1983). 

All Fe oxides and oxohydroxides are scarcely soluble. The solubility usually follows the order ferrihydrite > maghemite > lepidocrocite > hematite > goethite (Schwertmann and Taylor 1989), which obviously is the order of the relative thermodynamic stability of these minerals. The reported solubility products of actual samples, however, show important variations due to differences in particle size and... 

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