What is Iron Oxide?
Iron oxide, which is also called ferric oxide, is an inorganic compound having the chemical formula Fe2O3. It is one of the 3 major oxides of iron, and the remaining two being iron(II) oxide (FeO), which is the rare iron (II, and III) oxide (Fe3O4), and also naturally takes place as the mineral magnetite. Since the mineral is referred to as hematite, Fe2O3 is iron’s primary source for the steel industry and is readily attacked by acids. Often, iron oxide can be referred to as rust. This label is useful to some extent because rust shares many properties and has the same composition. But, in chemistry, rust is considered an ill-defined material, which can be described as Hydrous ferric oxide.
Brief Explanation about Iron Oxide
Iron oxide is a compound made from iron and oxygen. There are 16 known iron oxides and oxyhydroxides, the most famous of which is rust, a type of ferric oxide. Iron oxides and oxyhydroxides are widespread and play important roles in many geological and biological processes. They are used in iron ore, pigments, catalysts, thermites and are contained in hemoglobin. Iron oxide is a cheap and permanent pigment found in paints, coatings, and colored concrete. Commonly available colors are on the "soil" edge of the yellow / orange / red / brown / black range. When used as a food coloring, the E number is E172.
Structure
Iron oxide Structure – Fe2O3
Iron oxide Structure – Fe2O3
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Properties of Iron Oxide
Physical Properties
Physical Properties of Iron oxide – Fe2O3
Chemical Properties of Iron Oxide – Fe2O3
Iron oxide reacts with water in order to produce iron hydroxide.
\[ Fe_{2}O_{3} + H_{2}O \rightarrow Fe (OH)_{3}\]
Iron (III) oxide reacts with sulphuric acid to produce iron (III) sulfate and water.
\[ Fe_{2}O_{3} + H_{2}SO_{4} \rightarrow Fe_{2} (SO_{4})_{3} + H_{2}O \]
Preparation of Iron Oxide
Iron(III) oxide is the oxidation of the iron products, where it can be prepared in the laboratory by electrolyzing sodium bicarbonate solution, which is an inert electrolyte including an iron anode:
\[ 4Fe + 3O_{2} + 2H_{2}O \rightarrow 4 FeO(OH) \]
The resultant hydrated iron(III) oxide can be written as FeO(OH), which dehydrates around 200 °C.
\[ 2 FeO(OH) \rightarrow Fe_{2}O_{3} + H_{2}O \]
Reactions
One of the most important reactions of iron oxides is its carbothermal reduction that gives iron, used in steel-making:
\[ Fe_{2}O_{3} + 3CO \rightarrow 2Fe + 3CO_{2} \]
The other redox reaction is with aluminum, which is an extremely exothermic thermite reaction.
\[ 2 Al + Fe_{2}O_{3} \rightarrow 2 Fe + Al_{2}O_{3} \]
We can use this process to weld the thick metals including rails of train tracks with the help of a ceramic container to funnel the molten iron in between 2 sections of the rail. Thermite can also be used in making small-scale cast-iron sculptures, weapons, and tools.
Partial reduction, along with the hydrogen compound at around 400 0C will produce magnetite, which is referred to as a black magnetic material. It contains both Fe(III) and Fe(II):
\[ 3 Fe_{2}O_{3} + H_{2} \rightarrow 2 Fe_{3}O_{4} + H_{2}O \]
The Iron(III) oxide results in insoluble water, but it readily dissolves in strong acid. For example, sulfuric and hydrochloric acids. It also dissolves well in the solutions of chelating agents like oxalic acid and EDTA.
Heating the iron(III) oxide with other carbonates or metal oxides yields materials called ferrates (ferrate (III)):
\[ ZnO + Fe_{2}O_{3} \rightarrow Zn(FeO_{2})_{2}\]
Uses of Iron Oxide – Fe2O3
Common black iron oxide is used in both copper plates and stamp embossed inks.
Iron oxide forms the main component of products in the pharmaceutical, paint, plastic, ink and cosmetics industries.
It is used as a naturally occurring pigment containing titanium dioxide.
The salt is used as a flocculant in wastewater treatment, fiber dyeing, fertilizer and feed additive production.
Used as an abrasive in the jewelry industry.
Other Uses of Iron Oxide Fe2O3
Let us look at the uses of iron oxide in various industries, listed below.
Iron Industry
The overwhelming iron(III) oxide application is the feedstock of the iron and steel industries. For example, the production of steel, iron, and several alloys.
Polishing
A very fine powder of the ferric oxide is called "red rouge," "jeweler’s rouge," or just as a rogue. It can be used to put the final polish on the lenses and metallic pieces of jewelry, and historically, as a cosmetic. This rouge cuts more slowly than a few modern polishes, like cerium(IV) oxide, but still, it is used by jewelers for the superior finish it can produce and in the optics fabrication. The rouge slightly stains the gold when polishing gold, which contributes to the appearance of the finished piece.
Pigment
Iron oxide can also be used as a pigment, under the names "Pigment Brown 6", "Pigment Brown 7", "Pigment Red 101". A few of them as examples are Pigment Brown 6, Pigment Red 101, which are approved by the US Food & Drug Administration - FDA, for cosmetics use. In addition, iron oxides can be used as pigments in dental composites alongside titanium oxides.
Hematite is one of the characteristic components of the Swedish paint color Falu red.
Medicine
Calamine lotion, which is used to treat mild itchiness, is chiefly composed of a combination of zinc oxide, by acting as an astringent, and around 0.5% iron(III) oxide, the active ingredient of the product, acting as an antipruritic. The red color iron(III) oxide is also primarily and widely responsible for the familiar pink color lotion.
FAQs on Iron Oxide
1. Explain the difference between Fe2O3 and Fe3O4?
Both of these compounds are ferrous oxides. Therefore, Fe2O3 can be given as a simple oxide, where Fe in Ferric oxide results in only +3 in the oxidation state, and hence, Fe3O4 is a mixed oxide, where the Fe in Ferrous oxide exists in both +2 and +3 oxidation states. Although, we can compose Fe3O4 as FeO. And, Fe2O3 can be written as iron oxide (II), whereas, Fe3O4 can be written as iron oxide (II, III).
2. Explain if the iron oxide is toxic to humans?
When we breathe iron oxide, it will impact us. Exposure to the fumes from Iron Oxide may cause fever from metal fumes. This is explained as a flu-like condition with metallic taste signs, aches, fever and chills, cough, and chest tightness. However, Ferrous Oxide (FeO) is highly flammable and reactive and can combust spontaneously in the air.
3. What is the black iron oxide used for?
Black iron oxide, which is also called magnetite, can be used for resistance and as well as corrosion. Black iron oxide can often be used in anti-corrosion paints, which are found in several bridges and also in Eiffel Tower. These are used to shorten the proton relaxation times (T1, T2, and T2) as a contrast agent in the imaging of magnetic resonance.
4. What is iron oxide made of?
Iron oxide is a compound consisting of iron and oxygen. There are 17 known iron oxides and oxyhydroxides, of which rust, a type of iron (III) oxide, is best known. Iron oxides and oxyhydroxides are widely distributed in nature and play important roles in many geological and biological processes.
5. Is iron oxide used in food?
Iron oxides are widely used as industrial food pigments to color sweets, olives, or cheese rinds (EFSA, 2015). The European Union classifies iron oxides as food additives with the number E172 (EU, 2008). Iron oxides are generally considered safe food pigments with low acute toxicity.
6. What do we use iron oxide for?
They are used as iron ores, pigments, catalysts, and in thermite, and occur in hemoglobin. Iron oxides are inexpensive and durable pigments in paints, coatings and coloured concrete. The Colors that are commonly available are in the "earthy" end of the yellow/orange/red/brown/black range.
7. Is iron oxide safe for skin?
Iron oxide is a naturally occurring mineral known to be safe, mild and non-toxic to the surface of the skin. One of the oldest tricks in skin care books is to use inorganic pigments such as iron oxide to improve the appearance of skin, usually red, orange, brown and black. With the right level of titanium oxide (white) and a little alchemy, prescribers can create products that cover imperfections and give everyone a uniform skin tone.
8. Is iron oxide natural?
Iron oxide pigments, which may be natural or synthetic, have been used as colorants since early humans began painting on cave walls. Natural pigments are derived from several iron oxide minerals: Red pigments are derived from hematite. Yellow and brown pigments — ochres, sierras, and numbers — are derived from limonite. Magnetite provides a black iron oxide pigment. A micaceous iron oxide is a special form of hematite that occurs in thin metallic gray platelets or flakes. Synthetic pigments are manufactured under controlled conditions such that particle size, distribution, and shape can be accurately replicated; resulting in superior uniformity, color quality, and chemical purity.
