common sources of ion of iron(III) cation vs chromium(III) cation

iron(III) cation chromium(III) cation | common sources of ion

iron(III) cation | iron phosphide (3:1) (1 eq) | iron(III) sulfate hydrate (2 eq) | iron(III) phosphate tetrahydrate (1 eq) | iron(III) perchlorate hydrate (1 eq) | iron(III) oxalate hexahydrate (2 eq) | iron(III) nitrate nonahydrate (1 eq) | hemin (1 eq) | diironnonacarbonyl (1 eq) chromium(III) cation | tricarbonyl(mesitylene)chromium(0) (1 eq) | chromium(III) phosphate hydrate (1 eq) | chromium(III) nitrate nonahydrate (1 eq)