Difference Between Fe2O3 and Fe3O4

Fe₂O₃ vs Fe₃O₄
 

The difference between Fe₂O₃ and Fe₃O₄ can be discussed in terms of their chemical as well as physical properties and usage. Both of these minerals are naturally occurring iron oxides. But, most of their properties and usages are different to each other. The natural form of Fe₂O₃ is called hematite, and that of Fe₃O₄ is called magnetite. They both are colorful oxides with different colours, which are used as pigments and possess ferromagnetic properties.

What is Fe₂O₃?

The mineral form of Fe₂O₃ is called hematite or haematite. The IUPAC name of this compound is iron (III) oxide, also known as ferric oxide. It is an inorganic compound that has several phases of crystal structures. It is dark red in color.

Fe₂O₃ is the main source of iron in steel and iron industry, and it is used to produce some alloys. The fine powder of Fe₂O₃ is a polishing agent for metallic jewelry and lenses. Fe₂O₃, when used as a pigment, has different names. Those names are “Pigment Brown 6,” “Pigment Brown 7,” and “Pigment Red 101.” They are used in medical activities and in paint industry. For example, “Pigment Brown 6” and “Pigment Red 101” are FDA (Food and Drug Administration) approved colours and used to make cosmetics. A combination of iron oxides and titanium oxide is used as a pigment in dental composite.

What is Fe₃O₄?

Fe₃O₄ contains both Fe²⁺ and Fe³⁺ ions. Therefore, it is called Iron (II) (III) oxide. The IUPAC name of Fe₃O₄ is iron (II) iron (III) oxide. It is also known as ferrous-ferric oxide. It can be formed by FeO and Fe₂O₃, The natural form of this mineral is magnetite. It possesses magnetic properties and it is the most magnetic mineral found on the earth. It naturally occurs in almost all igneous and metamorphic rocks as small grains. It is black or brownish-black in colour with a metallic luster.

There are several commercial usages of Fe₃O₄. It is a catalyst in industrial synthesis of ammonia using “Haber process.” It is also used to make black pigment called C.I pigment black 11 (C.I. No.77499). Nano-particles of Fe₃O₄ are used in MRI scanning process as a contrasting agent. The powdered form of Fe₃O₄ is a good sorbent; it removes arsenic (III) and arsenic (V) from water.

What is the difference between Fe₂O₃ and Fe₃O₄?

• Structure:

• The Fe₂O₃ has several crystal forms as alpha phase, gamma phase, and other phases. Alpha-Fe₂O₃ has the rhombohedral structure, gamma- Fe₂O₃ has the cubic structure, and beta phase has cubic body-centered structure.

• The crystal structure of Fe₃O₄ is “cubic inverse spinel structure.”

• Oxidation state of iron (Fe):

• In Fe₂O₃ , the oxidation state of iron is (+III).

• Fe₃O₄ contains both (+II) and (+III) oxidation states.

• Colour:

• Fe₂O₃ is dark red in colour. It appears as a red-brown solid.

• Fe₃O₄ has a brownish-black colour with a metallic luster.

• Electrical Conductivity:

• The electrical conductivity of Fe₃O₄ is significantly higher (* 106) than Fe₂O₃. The reason for this property is due to the ability to exchange electrons between Fe²⁺ and Fe³⁺ centers in Fe₃O₄.

• As a Pigment:

• Fe₂O₃ produces several colours as a pigment; “Pigment Brown 6,” “Pigment Brown 7,” and “Pigment Red 101.”

• Fe₃O₄ is used to make black color pigment called C.I pigment black 11.

Images Courtesy:

1. Sample of iron(III) oxide via Wikicommons (Public Domain)
2. Fe3O4 by Leiem (CC BY-SA 4.0)