Iron

On this week's episode of the "I Can't Sleep" podcast, I dive headfirst into the riveting world of... iron. Yes, folks, you heard it right. Nothing screams "sweet dreams" like a dense, in-depth exploration into the world of this naturally occurring element.

It's all there: the atomic number (26 - spoiler alert!), the atomic weight, and even a riveting discussion about oxidation states. If you can stay awake through that, you're stronger than most. Happy sleeping!

Transcript

Welcome to the I Can't Sleep Podcast,

A Glassbox Media Podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host,

Benjamin Boster.

Today's episode is from a Wikipedia article titled,

Iron.

Iron is a chemical element with the symbol Fe from Latin ferrum,

Iron,

And atomic number 26.

It is a metal that belongs to the first transition series and group 8 of the periodic table.

It is,

By mass,

The most common element on Earth,

Just ahead of oxygen,

32.

1% and 30.

1% respectively,

Forming much of Earth's outer and inner core.

It is the fourth most common element in the Earth's crust,

Being mainly deposited by meteorites in its metallic state,

With its ore also being found there.

Extracting usable metal from iron ores requires kilns or furnaces capable of reaching 1,

500 degrees Celsius or higher,

About 500 degrees Celsius higher than that required to smelt copper.

Humans started to master that process in Eurasia during the second millennium BCE,

And the use of iron tools and weapons began to displace copper alloys,

In some regions only around 1200 BCE.

That event is considered the transition from the Bronze Age to the Iron Age.

In the modern world,

Iron alloys such as steel,

Stainless steel,

Cast iron,

And special steels are by far the most common industrial metals,

Due to their mechanical properties and low cost.

The iron and steel industry is thus very important economically,

And iron is the cheapest metal,

With a price of a few dollars per kilogram or pound.

Pristine and smooth pure iron surfaces are a mirror-like silvery gray.

Iron reacts readily with oxygen and water to produce brown to black hydrated iron oxides,

Commonly known as rust.

Unlike the oxides of some other metals that form passivating layers,

Rust occupies more volume than the metal and thus flakes off,

Exposing more fresh surfaces for corrosion.

High purity irons,

I.

E.

Electrolytic iron,

Are more resistant to corrosion.

The body of an adult human contains about 4 grams,

0.

005% body weight of iron,

Mostly in hemoglobin and myoglobin.

These two proteins play essential roles in vertebrate metabolism,

Respectively oxygen transport by blood,

And oxygen storage in muscles.

To maintain the necessary levels,

Human iron metabolism requires a minimum of iron in the diet.

Iron is also the metal at the active site of many important redox enzymes,

Dealing with cellular respiration and oxidation and reduction in plants and animals.

Chemically,

The most common oxidation states of iron are iron 2 and iron 3.

Iron shares many properties of other transition metals,

Including the other group 8 elements,

Ruthenium and osmium.

Iron forms compounds in a wide range of oxidation states,

Negative 2 to plus 7.

Iron also forms many coordination compounds,

Some of them such as ferrocene,

Ferroxylate,

And prussian blue,

Have substantial industrial,

Medical,

Or research applications.

Characteristics Allotropes At least four allotropes of iron differing atom arrangements in the solid are known,

Conventionally denoted α,

Γ,

Δ,

Ε.

The first three forms are observed at ordinary pressures.

As molten iron cools past its freezing point of 1538 °C,

It crystallizes into its δ allotrope,

Which has a body-centered cubic BCC crystal structure.

As it cools further to 1394 °C,

It changes to its γ-iron allotrope,

A face-centered cubic FCC crystal structure,

Or austenite.

At 912 °C and below,

The crystal structure again becomes the BCC α-iron allotrope.

The physical properties of iron at very high pressures and temperatures have also been studied extensively because of their relevance to theories about the cores of the Earth and other planets.

Above approximately 10 GPa and temperatures of a few hundred Kelvin or less,

Α-iron changes into another hexagonal close-packed HCP structure,

Which is also known as ε-iron.

The higher temperature γ-phase also changes into ε-iron,

But does so at higher pressure.

Some controversial experimental evidence exists for a stable β-phase at pressures above 50 GPa and temperatures of at least 1500 Kelvin.

It is supposed to have an orthorhombic or a double HCP structure.

Confusingly,

The term β-iron is sometimes also used to refer to α-iron above its Curie point when it changes from being ferromagnetic to paramagnetic,

Even though its crystal structure has not changed.

The inner core of the Earth is generally presumed to consist of an iron-nickel alloy with ε- or β- structure.

Melting and boiling points The melting and boiling points of iron along with its enthalpy of atomization are lower than those of the earlier third elements from scandium to chromium,

Showing the lessened contribution of the third electrons to metallic bonding as they are attracted more and more into the inert core by the nucleus.

However,

They are higher than the values for the previous element manganese because that element has a half-filled third subshell and consequently its d-electrons are not easily delocalized.

This same trend appears for ruthenium but not osmium.

The melting point of iron is experimentally well defined for pressures less than 50 GPa.

For greater pressures,

Published data still varies by tens of GPa and over 1000 Kelvin.

Magnetic properties Below its Curie point of 770 °C,

Α- iron changes from paramagnetic to ferromagnetic.

The pins of the two unpaired electrons in each atom generally align with the pins of its neighbors,

Creating an overall magnetic field.

This happens because the orbits of those two electrons do not point toward neighboring atoms in the lattice and therefore are not involved in metallic bonding.

In the absence of an external source of magnetic field,

The atoms get spontaneously partitioned into magnetic domains,

About 10 micrometers across,

Such that the atoms in each domain have parallel spins but some domains have other orientations.

Thus,

A macroscopic piece of iron will have a nearly zero overall magnetic field.

Application of an external magnetic field causes the domains that are magnetized in the same general direction to grow at the expense of adjacent ones that point in other directions reinforcing the external field.

This effect is exploited in devices that need to channel magnetic fields to fulfill design function such as electrical transformers,

Magnetic recording heads,

And electric motors.

Impurities,

Lattice defects,

Or grain and particle boundaries can pin the domains in the new positions so that the effect persists even after the external field is removed,

Thus turning the iron object into a permanent magnet.

Similar behavior is exhibited by some iron compounds such as the ferrites including the mineral magnetite,

A crystalline form of the mixed iron 2 and 3 oxide Fe3O4,

Although the atomic scale mechanism ferromagnetism is somewhat different.

Particles of magnetite with natural permanent magnetization,

Iodestones,

Provided the earliest compasses for navigation.

Particles of magnetite were extensively used in magnetic recording media such as core memories,

Magnetic tapes,

Floppies,

And discs until they were replaced by cobalt-based materials.

Isotopes This list has four stable isotopes,

Fe 5.

845% of natural iron,

54 Fe 5.

845% of natural iron,

56 Fe 91.

754%,

57 Fe 2.

119%,

And 58 Fe 0.

282%.

Twenty-four artificial isotopes have also been created,

Of these stable isotopes only 57 Fe has a nuclear spin,

Minus one half.

The nuclide 54 Fe theoretically can undergo double electron capture to 54 Cr,

But the process has never been observed and only a lower limit on the half-life of 3.

1 x 1022 years has been established.

60 Fe is an extinct radionuclide of long half-life,

2.

6 million years.

It is not found on Earth,

But its ultimate decay product is its granddaughter,

The stable nuclide 60 Ni.

Much of the past work on isotopic composition of iron has focused on the nucleosynthesis of 60 Fe through studies of meteorites and ore formation.

In the last decade,

Advances in mass spectrometry have allowed the detection and quantification of minute naturally occurring variations in the ratios of the stable isotopes of iron.

Much of this work is driven by the Earth and planetary science communities,

Although applications to biological and industrial systems are emerging.

In phases of the meteorites Semarcona and Chervonnikud,

A correlation between the concentration of 60 Ni,

The granddaughter of 60 Fe,

And the abundance of the stable iron isotopes provided evidence for the existence of 60 Fe at the time of formation of the solar system.

Possibly the energy released by the decay of 60 Fe along with that released by 26Al contributed to the remelting and differentiation of asteroids after their formation 4.

6 billion years ago.

The abundance of 60 Ni present in extraterrestrial material may bring further insight into the origin and early history of the solar system.

The most abundant iron isotope,

56 Fe,

Is of particular interest to nuclear scientists because it represents the most common endpoint of nucleosynthesis.

Since 56 Ni,

14 alpha particles,

Is easily produced from lighter nuclei in the alpha process in nuclear reactions,

In supernovae,

It is the endpoint of fusion chains inside extremely massive stars,

Since addition of another alpha particle resulting in 60 Zn requires a great deal more energy.

This 56 Ni,

Which has a half-life of about 6 days,

Is created in quantity in these stars,

But soon decays by two successive positron emissions within supernova decay products in the supernova remnant gas cloud,

First to radioactive 56 CO and then to stable 56 Fe.

As such,

Iron is the most abundant element in the core of red giants and is the most abundant material in iron meteorites and in the dense metal cores of planets,

Such as Earth.

It is also very common in the universe,

Relative to other stable metals of approximately the same atomic weight.

Iron is the sixth most abundant element in the universe and the most common refractory element.

Although a further tiny energy gain could be extracted by synthesizing 62 Ni,

Which has a marginally higher binding energy than 56 Fe,

Conditions in stars are unsuitable for this process.

Element production in supernovas greatly favor iron over nickel,

And in any case,

56 Fe still has a lower mass per nucleon than 62 Ni due to its higher fraction of lighter protons.

Hence elements heavier than iron require a supernova for their formation,

Involving rapid neutron capture by starting 56 Fe nuclei.

In the far future of the universe,

Assuming that proton decay does not occur,

Cold fusion occurring via quantum tunneling would cause the light nuclei in ordinary matter to fuse into 56 Fe nuclei.

Fission and alpha particle emission would then make heavy nuclei decay into iron,

Converting all stellar mass objects to cold spheres of pure iron.

Origin and Occurrence in Nature Cosmogenesis Iron's abundance in rocky planets like Earth is due to its abundant production during the runaway fusion and explosion of Type 1a supernovae,

Which scatters the iron into space.

Metallic Iron Metallic or native iron is rarely found on the surface of the Earth because it tends to oxidize.

However,

Both the Earth's inner and outer core,

Which together account for 35% of the mass of the whole Earth,

Are believed to consist largely of an iron alloy,

Possibly with nickel.

Electric currents in the liquid outer core are believed to be the origin of the Earth's magnetic field.

The other terrestrial planets,

Mercury,

Venus,

And Mars,

As well as the Moon,

Are believed to have a metallic core consisting mostly of iron.

The M-type asteroids are also believed to be partly or mostly made of a metallic iron alloy.

The rare iron meteorites are the main form of natural metallic iron on the Earth's surface.

Items made of cold-work meteoritic iron have been found in various archaeological sites dating from a time when iron smelting had not yet been developed,

And the Inuit in Greenland have been reported to use iron from the Cape York meteorite for tools and hunting weapons.

About 1 in 20 meteorites consist of the unique iron-nickel minerals tannide,

35-80% iron,

And kamacite,

90-95% iron.

Native iron is also rarely found in basalts that have formed from magmas that have come into contact with carbon-rich sedimentary rocks,

Which have reduced the oxygen fugacity sufficiently for iron to crystallize.

This is known as Telluric iron and is described from a few localities such as Disko Island in West Greenland,

Yakutia in Russia,

And Buhl in Germany.

Natural Minerals Ferropericlase,

MgFeO,

A solid solution of periclase,

MgO,

And vustite,

FeO,

Makes up about 20% of the volume of the lower mantle of the Earth,

Which makes it the second most abundant mineral phase in that region after silicate perovskite,

MgFeSiO3.

It also is the major host for iron in the lower mantle.

Silicate perovskite may form up to 93% of the lower mantle,

And the magnesium iron form MgFeSiO3 is considered to be the most abundant mineral in the Earth,

Making up 38% of its volume.

Earth's Crust While iron is the most abundant element on Earth,

Most of this iron is concentrated in the inner and outer cores.

The fraction of iron that is Earth's crust only amounts to about 5% of the overall mass of the crust,

And is thus only the fourth most abundant element in that layer,

After oxygen,

Silicon,

And aluminum.

Most of the iron in the crust is combined with various other elements to form many iron minerals.

An important class is the iron oxide minerals such as hematite,

Fe2O3,

Magnetite,

Fe3O4,

And siderite,

FeCO3,

Which are the major ores of iron.

Many igneous rocks also contain the sulfide minerals pyritite and pentalentite.

During weathering,

Iron tends to leach from sulfide deposits as the sulfate,

And from silicate deposits as the bicarbonate.

Both of these are oxidized in aqueous solution,

And precipitate an even mildly elevated pH as Fe3O3.

Large deposits of iron are banded iron formations,

A type of rock consisting of repeated thin layers of iron oxides alternating with bands of iron pore shale and chert.

The banded iron formations were laid down in the time between 3,

700 million years ago and 1,

800 million years ago.

Materials containing finely ground iron 3 oxides of oxide hydroxides,

Such as ochre,

Have been used as yellow,

Red,

And brown pigments since prehistorical times.

They contribute as well to the color of various rocks and clays,

Including entire geological formations like the Painted Hills in Oregon and Bunstenstein colored sandstone,

British Bunter.

Through Eisenstein,

A Jurassic iron sandstone,

E.

G.

From Donsdorf in Germany,

And Bathstone in the UK,

Iron compounds are responsible for the yellowish color of many historical buildings and sculptures.

The proverbial red color of the surface of Mars is derived from an iron oxide-rich regolith.

Significant amounts of iron occur in the iron sulfide mineral pyrite,

FeS2,

But it is difficult to extract iron from it and is therefore not exploited.

In fact,

Iron is so common that production generally focuses only on ores with very high quantities of it.

According to the International Resource Panel's Metal Stocks and Society Report,

The global stock of iron in use in society is 2,

200 kg per capita.

More developed countries differ in this respect from less developed countries.

7,

000-14,

000 vs.

2,

000 kg per capita.

Oceans Ocean science demonstrated the role of the iron in the ancient seas in both marine biota and climate.

Chemistry and Compounds Iron shows the characteristic chemical properties of the transition metals,

Namely the ability to form variable oxidation states differing by steps of one,

And a very large coordination in organometallic chemistry.

Indeed,

It was the discovery of an iron compound,

Fluorescein,

That revolutionized the latter field in the 1950s.

Iron is sometimes considered as a prototype for the entire block of transition metals due to its abundance and the immense role it has played in the technological progress of humanity.

Its 26 electrons are arranged in the configuration Ar3d64s2,

Of which the 3d and 4s electrons are relatively close in energy,

And thus a number of electrons can be ionized.

Iron forms compounds mainly in the oxidation states plus-2,

Iron-2-ferrous,

And plus-3,

Iron-3-ferric.

Iron also occurs in higher oxidation states,

I.

E.

The purple potassium ferrate K2FeO4,

Which contains iron in its plus-6 oxidation state.

The anion FeO4- with iron in its plus-7 oxidation state,

Along with an iron-5 peroxoisomer,

Has been detected by infrared spectroscopy at 4K after co-condensation of laser-ablated Fe atoms with a mixture of O2-Ar.

Iron-4 is a common intermediate in many biochemical oxidation reactions.

Numerous organo-iron compounds contain formal oxidation states of plus-1,

0,

Negative-1,

Or even negative-2.

The oxidation states and other bonding properties are often assessed using the technique of Musbauer spectroscopy.

Many mixed valence compounds contain both iron-2 and iron-3 centers,

Such as magnetite and Prussian blue,

Fe4FeCn6-3.

The latter is used as the traditional blue in blueprints.

Iron is the first of the transition metals that cannot reach its group oxidation state of plus-8,

Although its heavier congeners ruthenium and osmium can,

With ruthenium having more difficulty than osmium.

Ruthenium exhibits an aqueous cationic chemistry in its low oxidation states similar to that of iron,

But osmium does not,

Favoring high oxidation states in which it forms anionic complexes.

In the second half of the 3D transition series,

Vertical similarities down the groups compete with the horizontal similarities of iron with its neighbors cobalt and nickel in the periodic table,

Which are also ferromagnetic at room temperature and share similar chemistry.

As such,

Iron,

Cobalt,

And nickel are sometimes grouped together as the iron triad.

Unlike many other metals,

Iron does not form amalgams with mercury.

As a result,

Mercury is traded in standardized 76-pound flasks made of iron.

Iron is by far the most reactive element in its group.

It is pyrophoric when finely divided and dissolves easily in dilute acids,

Giving Fe2+.

However,

It does not react with concentrated nitric acid and other oxidizing acids due to the formation of an impervious oxide layer,

Which can nevertheless react with hydrochloric acid.

High purity iron,

Called electrolytic iron,

Is considered to be resistant to rust due to its oxide layer.

Binary Compounds Oxides and Sulfides Iron forms various oxide and hydroxide compounds.

The most common are Fe2O3,

Fe3O4,

And Fe2O3.

Iron 2 oxide also exists,

Though it is unstable at room temperature.

Despite their names,

They are actually all non-stoichiometric compounds whose compositions may vary.

These oxides are the principal ores for the production of iron.

They are also used in the production of ferrites,

Useful magnetic storage media in computers and pigments.

The best known sulfide is Fe2Pi,

Also known as fool's gold owing to its golden luster.

Halides The binary ferrous and ferric halides are well known.

The ferrous halides typically arise from treating iron metal with the corresponding hydrohalic acid to give the corresponding hydrated salts.

Iron reacts with fluorine,

Chlorine,

And bromine to give the corresponding ferric halides,

Ferric chloride being the most common.

Ferric iodide is an exception,

Being thermodynamically unstable due to the oxidizing power of Fe3+,

And the high reducing power of I-.

Ferric iodide is not stable in ordinary conditions,

But can be prepared through the reaction of iron pentacarbonyl with iodine and carbon monoxide in the presence of hexane and light at the temperature of minus 20 degrees Celsius,

With oxygen and water excluded.

Uses of ferric iodide with some soft bases are known to be stable compounds.

Organometallic compounds Organo-iron chemistry is the study of organometallic compounds of iron,

Where carbon atoms are covalently bound to the metal atom.

There are many and varied,

Including cyanide complexes,

Carbonyl complexes,

Sandwich and half-sandwich compounds.

Russian blue or ferric ferrocyanide,

Fe4FeCN6-3,

Is an old and well-known iron cyanide complex,

Extensively used as pigment and in several other applications.

Its formation can be used as a simple wet chemistry test to distinguish between aqueous solutions of Fe2+,

And Fe3+,

Respectively with potassium ferrocyanide and potassium ferrocyanide to form Prussian blue.

Another old example of an organo-iron compound is iron pentacarbonyl,

FeCO5,

In which a neutral iron atom is bound to the carbon atoms of five carbon monoxide molecules.

The compound can be used to make carbonyl iron powder,

A highly reactive form of metallic iron.

Thermolysis of iron pentacarbonyl gives tri-iron dodecacarbonyl Fe3CO12,

A complex with a cluster of three iron atoms at its core.

Coleman's reagent disodium tetracarbonyl ferrate is a useful reagent for organic chemistry.

It contains iron in the minus-2 oxidation state.

History Development of iron metallurgy Iron is one of the elements undoubtedly known to the ancient world.

It has been worked or wrought for millennia.

However,

Iron artifacts of great age are much rarer than objects made of gold or silver due to the ease with which iron corrodes.

The technology developed slowly and even after the discovery of smelting,

It took many centuries for iron to replace bronze as the metal of choice for tools and weapons.

Meteoric Iron Beads made from meteoric iron in 3500 BC or earlier were found in Gerza,

Egypt,

By G.

A.

Wainwright.

The beads contain 7.

5% nickel,

Which is a signature of meteoric origin since iron found in the earth's crust generally has only minuscule nickel impurities.

Meteoric iron was highly regarded due to its origin in the heavens and was often used to forge weapons and tools.

For example,

A dagger made of meteoric iron was found in the tomb of Tutankhamun,

Containing similar properties of iron,

Cobalt,

And nickel to a meteorite discovered in the area,

Deposited by an ancient meteor shower.

Items that were likely made of iron by Egyptians date from 3000 to 2000 BC.

Meteoric iron is comparably soft and ductile and easily cold forged,

But may get brittle when heated because of the nickel content.

Rot Iron The first iron production started in the Middle Bronze Age,

But it took several centuries before iron displaced bronze.

Samples of smelted iron from Asmar,

Mesopotamia and Tal Chagar Bazar in northern Syria were made sometime between 3000 and 2700 BC.

The Hittites established an empire in north-central Anatolia around 1600 BC.

They appear to be the first to understand the production of iron from its ores and regard it highly in their society.

The Hittites began to smelt iron between 1500 and 1200 BC,

And the practice spread to the rest of the Near East after their empire fell in 1180 BC.

The subsequent period is called the Iron Age.

Artifacts of smelted iron are found in India,

Dating from 1800 to 1200 BC,

And in the Levant from about 1500 BC,

Suggesting smelting in Anatolia or the Caucasus.

Alleged references to iron in the Indian Vedas has been used for claims of a very early usage of iron in India,

Respectively to date the texts as such.

The Rig Veda terms ayas,

Metal,

Refers to copper,

While iron,

Which is called sayemas ayas,

Literally,

Black copper,

First is mentioned in the post-Rig Vedic Atharva Veda.

Some archaeological evidence suggests iron was smelted in Zimbabwe in southeast Africa as early as the 8th century BC.

Iron working was introduced to Greece in the late 11th century BC,

From which it spread quickly throughout Europe.

The spread of iron working in Central and Western Europe is associated with Celtic expansion.

According to Pliny the Elder,

Iron use was common in the Roman era.

In the lands of what is now considered China,

Iron appears approximately 700 to 500 BC.

Iron smelting may have been introduced in China through Central Asia.

The earliest evidence of the use of a blast furnace in China dates to the 1st century AD,

And cupola furnaces were used as early as the Warring States period,

403 to 221 BC.

Knowledge of the blast and cupola furnace remained widespread during the Tang and Song dynasties.

During the Industrial Revolution in Britain,

Henry Court began refining iron from pig iron to wrought iron,

Or bar iron,

Using innovative production systems.

In 1783,

He patented the puddling process for refining iron ore.

It was later improved by others,

Including Joseph Hall.

Cast Iron Cast iron was first produced in China during 5th century BC,

But was hardly in Europe until the medieval period.

The earliest cast iron artifacts were discovered by archaeologists in what is now modern Lühe County,

Jiangsu in China.

Cast iron was used in ancient China for warfare,

Agriculture,

And architecture.

During the medieval period,

Mains were found in Europe of producing wrought iron from cast iron,

In this context known as pig iron,

Using finery forges.

For all these processes,

Charcoal was required as fuel.

Medieval blast furnaces were about 10 feet tall and made of fireproof brick.

Forced air was usually provided by hand-operated bellows.

Modern blast furnaces have grown much bigger,

With hars 14 meters in diameter,

That allow them to produce thousands of tons of iron each day.

But essentially operate in much the same way as they did during medieval times.

In 1709,

Abraham Darby I established a coke-fired blast furnace to produce cast iron,

Replacing charcoal,

Although continuing to use blast furnaces.

The ensuing availability of inexpensive iron was one of the factors leading to the Industrial Revolution.

Toward the end of the 18th century,

Cast iron began to replace wrought iron for certain purposes.

Carbon content in iron was not implicated as a reason for the differences in properties of wrought iron,

Cast iron,

And steel until the 18th century.

Since iron was becoming cheaper and more plentiful,

It also became a major structural material following the building of the innovative First Iron Bridge in 1778.

This bridge still stands today as a monument to the role iron played in the Industrial Revolution.

Following this,

Iron was used in rails,

Boats,

Ships,

Aqueducts,

And buildings,

As well as in iron cylinders in steam engines.

Railways have been central to the formation of modernity and ideas of progress,

And various languages refer to railways as Iron Road.

Steel Steel,

With smaller carbon content than pig iron but more than wrought iron,

Was first produced in antiquity by using a bloomery.

Blacksmiths in Luristan in western Persia were making good steel by 1000 BC.

Then improved versions,

Wood steel by India and Damascus steel,

Were developed around 300 BC and AD 500 respectively.

These methods were specialized and so steel did not become a major commodity until the 1850s.

New methods of producing it by carburizing bars of iron in the cementation process were devised in the 17th century.

In the Industrial Revolution,

New methods of producing bar iron without charcoal were devised and these were later applied to produce steel.

In the late 1850s,

Henry Bessemer invented a new steelmaking process involving blowing air through molten pig iron to produce mild steel.

This made steel much more economical,

Thereby leading to wrought iron no longer being produced in large quantities.

Foundations of Modern Chemistry In 1774,

Antoine Lavoisier used the reaction of water-steam with metallic iron inside an incandescent iron tube to produce hydrogen in his experiments leading to the demonstration of the conservation of mass,

Which was instrumental in changing chemistry from a qualitative science to a quantitative one.

Symbolic Role Iron plays a certain role in mythology and has found various usage as a metaphor and in folklore.

The Greek poet Hesiod's works and days list different ages of man named after metals like gold,

Silver,

Bronze,

And iron to account for successive ages of humanity.

The Iron Age was closely related with Rome and in Ovid's Metamorphosis.

The virtues in despair quit the earth,

And the depravity of man becomes universal and complete.

Hard steel succeeded them.

Ovid,

Metamorphosis,

Book I,

Iron Age,

Line 160.

An example of the importance of iron's symbolic role may be found in the German Campaign of 1813.

Frederick William III commissioned then the first iron cross as military decoration.

Berlin iron jewelry reached its peak production between 1813 and 1815 when the Prussian royal family urged citizens to donate gold and silver jewelry for military funding.

The inscription,

Gold gab ich für Eisen,

I have gold for iron,

Was used as well in later war efforts.

Production of Metallic Iron,

Laboratory Routes For a few limited purposes when it's needed,

Pure iron is produced in the laboratory in small quantities by reducing the pure oxide of hydroxide with hydrogen,

Or forming iron pentacarbonyl and heating it to 250 degrees Celsius so that it decomposes to form pure iron powder.

Another method is electrolysis of ferrous chloride into an iron cathode.

Main Industrial Route Nowadays,

The industrial production of iron or steel consists of two main stages.

In the first stage,

Iron ore is reduced with coke in a blast furnace and the molten metal is separated from gross impurities such as silicate minerals.

This stage yields an alloy,

Pig iron,

That contains relatively large amounts of carbon.

In the second stage,

The amount of carbon in the pig iron is lowered by oxidation to yield wrought iron,

Steel,

Or cast iron.

Other metals can be added at this stage to form alloy steels.

Blast Furnace Processing The blast furnace is loaded with iron ores,

Usually hematite Fe2O3 or magnetite Fe3O4,

Along with coke,

Coal that has been separately baked to remove volatile components,

And flux,

Limestone,

Or dolomite.

Blasts of air preheated to 900 degrees Celsius,

Sometimes with oxygen enrichment,

Is blown through the mixture in sufficient amount to turn the carbon into carbon monoxide.

This reaction raises the temperature to about 2000 degrees Celsius.

The carbon monoxide reduces the iron ore to metallic iron.

Some iron in the high temperature lower region of the furnace reacts directly with the coke.

The flux removes silicaceous minerals in the ore,

Which would otherwise clog the furnace.

The heat of the furnace decomposes the carbonates to calcium oxide,

Which reacts with any excess silica to form a slag composed of calcium silicate,

CaSiO3,

Or other products.

At the furnace's temperature,

The metal and the slag are both molten.

They collect at the bottom as two immiscible liquid layers with the slag on top,

That are then easily separated.

The slag can be used as a material in road construction or to improve mineral-poor soils for agriculture.

Steelmaking thus remains one of the largest industrial contributors of CO2 emissions in the world.

Steelmaking The pig iron produced by the blast furnace process contains up to 4-5% carbon by mass,

With small amounts of other impurities like sulfur,

Magnesium,

Phosphorus,

And manganese.

This high level of carbon makes it relatively weak and brittle.

Increasing the amount of carbon to 0.

002-2.

1% produces steel,

Which may be up to 1000 times harder than pure iron.

A great variety of steel articles can then be made by cold working,

Hot rolling,

Forging,

And machining,

Etc.

Removing the impurities from pig iron,

But leaving 2-4% carbon results in cast iron,

Which is cast by foundries into articles such as stoves,

Pipes,

Radiators,

Lamp posts,

And rails.

Steel products often undergo various heat treatments after they are forged to shape.

Annealing consists of heating them to 700-800 degrees Celsius for several hours,

And then gradual cooling.

It makes the steel softer and more workable.

Reviews

Magnetic. 🪨 The ones about nature and natural elements are my favorites. I go back to them over and over. 🙏

The first time I ever heard, you say your voice was soothing I was like oh yeah, cap. By the end I had thought you were understating

Thank you Benjamin. I listen to your podcasts when i go to bed, primarily to help me listen and take my mind off problems which helps me fall asleep. I pick topics that are of interest. Iron remindes me of science class (good memories), atomic tables etc. but pretty soon, I'm sound asleep. Woke at 4:09 am; listened again; same result. Mission accomplished.

So boring! 😝
Thank you as always Benjamin! 🤗🤗🤗🤗

I love all of these talks. Never make it to the end, so can’t really comment 😂