common sources of ion of nitrite anion vs iron(III) cation

nitrite anion iron(III) cation | common sources of ion

nitrite anion | sodium nitrite (1 eq) | sodium hexanitroiridate(III) (6 eq) | sodium hexanitrocobaltate(III) (6 eq) | silver nitrite (1 eq) | potassium tetranitroplatinate(II) (4 eq) | potassium tetranitropalladate(II) (4 eq) | potassium nitrite (1 eq) | potassium hexanitrorhodate(III) (6 eq) | potassium hexanitroiridate(III) (6 eq) 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)