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Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main source of iron for the steel industry. Fe2O3 is readily attacked by acids. Iron(III) oxide is often called rust, and to some extent this label is useful, because rust shares several properties and has a similar composition.

Iron(III) nitrate, or ferric nitrate, is the chemical compound with the formula Fe(NO3)3. Since it is deliquescent, it is commonly found in its nonahydrate form Fe(NO3)3·9H2O in which it forms colourless to pale violet crystals. When dissolved, it forms yellow solution due to hydrolysis.

Preparation

The compound is prepared by treating iron metal powder with nitric acid.

Fe + 4 HNO3 → Fe(NO3)3 + NO + 2 H2O.

Applications

In the chemical laboratory

Iron(III) chloride, also called ferric chloride, is an industrial scale commodity chemical compound, with the formula FeCl3 and with iron in the +3 oxidation state. The colour of iron(III) chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red. Anhydrous iron(III) chloride is deliquescent, forming hydrated hydrogen chloride mists in moist air. It is rarely observed in its natural form, the mineral molysite, known mainly from some fumaroles.