(From the Middle English iren) A white, malleable, ductile, metallic chemical element that can be readily magnetized and rusts rapidly in moist or salty air, forming mainly ferric oxide (Fe2O3) and ferric hydroxide (Fe(OH)3). It is vital to plant and animal life; the average human contains about four grams, much of which circulates as hemoglobin in the blood. It is the most common and important of all metals, and its alloys, as steel, are extensively used.

Symbol: Fe (from the Latin ferrum)
Atomic number: 26
Atomic weight: 55.847
Density (at room temperature and pressure): 7.87 g/cc
Melting point: 1,538°C
Boiling point: 2,861°C
Main valences: +2, +3
Ground state electron configuration: [Ar]3d64s2
Symbol: Fe
Atomic Number: 26
Boiling Point: 3023 K
Melting Point: 1808 K
Density at 300K: 7.874 g/cm3
Covalent radius: 1.17
Atomic radius: 1.72
Atomic volume: 7.10 cm3/mol
First ionization potental: 7.870 V
Specific heat capacity: 0.449 Jg-1K-1
Thermal conductivity: 80.2 Wm-1K-1
Electrical conductivity: 11.2 106Ω-1m-1
Heat of fusion: 13.8 kJ/mol
Heat of vaporization: 349.5 kJ/mol
Electronegativity: 1.83 (Pauling's)

Previous Manganese---Cobalt Next
To the Periodic Table
IRC = I = Iron Age

iron n.

Hardware, especially older and larger hardware of mainframe class with big metal cabinets housing relatively low-density electronics (but the term is also used of modern supercomputers). Often in the phrase big iron. Oppose silicon. See also dinosaur.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

Slang, 1920s

A motorcycle, among motorcycle enthusiasts.
An iron is a household appliance used to smooth out wrinkles and set creases in clothing and drapery. Typically an iron consists of a flat metal surface with holes in it, a plastic body which contains a well for water, and a handle. The metal surface is heated up to a high temperature (highest for cotton and other sturdy fabrics, lower for more delicate materials, particularly synthetics which have an unfortunate tendency to melt in high heat), and water is released through the vents as steam. The combination of heat and water vapor against the flat surfaces works to press the cloth very effectively. Irons are usually used on an ironing board, a small table with an insulated surface which prevents the heat from damaging it.

Today's irons are heated electrically, but irons certainly predate the era of easily available electricity. Traditional irons were indeed slabs of iron (with a handle of wood or some other material that wouldn't burn your hand), heated on a hot stove.

The word iron can also more generally denote a tool used in a similar way to heat and shape things - for instance, a soldering iron is a metal tool with a handle that is heated to a high temperature to melt solder to join objects - or to describe a tool made of (or traditionally made of) iron.

A certain amount of iron in one's diet is crucial for good health; in addition to it being a key component of the hemoglobin in red blood cells, the body needs iron to create myoglobin for muscles and to produce white blood cells. It also plays an important role in biochemical processes to produce energy. Adult women need 12-15 milligrams of iron a day, men need 8-15 milligrams, and children need about 10.

Dietary iron deficiency is the main cause of anemia. The National Institutes of Health estimates that 20% of women, 50% of pregnant women, and 3% of men are iron deficient. Women suffer more from chronic iron deficiency due to regular iron loss from menstruation.

Typical syptoms of iron deficiency include fatigue, bad temper, pale complexion, brittle nails, and weakness. Low-level deficiency may cause no obvious symptoms. Children with iron deficiency have been found to suffer from learning problems, attention deficits, and growth problems, so it's especially important that kids get the iron they need. Foods that are naturally rich in iron include beans and peas, meats (especially red meats), dark green leafy vegetables, blackstrap molasses, and whole grains. Eating foods rich in vitamin C (such as orange juice) in the same meal helps your body absorb the iron.

However, if one consumes much past the recommended daily allowance for one's age, size, and activity level, this mineral becomes unhealthy and even outright poisonous.

There are over 3,500 cases of acute iron poisoning in the the U.S. alone each year. Just a few iron-containing supplement pills can be deadly to an infant or small child: a fatal dose can be 600 milligrams or more. Acute iron poisoning first causes irritation and ulceration of the stomach lining. Once the blood gets loaded with the excess iron, it causes widespread damage to the heart, kidneys, liver, brain, and lungs. The treatment for iron poisoning is to give the victim a chelation agent intravenously.

Lower doses of iron can cause chronic poisoning; this is most often seen in people who have a genetic tendency toward storing excessive amounts of iron (hemochromatosis). Some people with chronic iron poisoning find that their skin turns dark bronze or takes on a grayish hue. People may also suffer from fatigue, upset stomach, and intestinal pain. Eventually, chronic poisoning damages the internal organs, particularly the spleen, liver, and kidneys (the kidney damage causes a type of diabetes known as "bronze diabetes").

But even lower amounts of excess iron can cause subtle damage to the heart.

In the early 90s, medical researchers found that, in middle-aged men, having excessive stores of iron, as indicated by the presence of the protein ferritin in the blood serum, increases the risk of developing ischemic heart disease (IHD) which leads to heart attacks.

Iron evidently promotes the creation of free radicals, and free radicals promote the oxidation of lipids, and oxidized lipids are thought to cause hardening of the arteries (atherosclerosis). The researchers also found a link between elevated levels of ferritin and the consumption of meat, a typically iron-rich food.

The significance of this study is that men (and postmenopausal women) who consume large quantities of iron-rich foods could be putting themselves at risk of developing heart disease. Also, people with hemochromatosis are at risk even if they consume little iron-rich food.

So in order to reduce the risk of heart disease, many older people might need to cut back on iron intake, and it may be further necessary to actively remove iron in some people. "Active removal" might involve such things as prescribing chelating agents or perhaps even bleeding the patient.

People who get too much iron because of genes or diet can do a couple of things to keep themselves healthy:

  1. Donate blood on a regular basis if your health allows
  2. Don't consume iron-rich foods along with vitamin C, as the vitamin vastly improves absorbtion of the mineral
  3. Drink tea -- the tannins in tea block iron absorbtion
  4. Drink cranberry juice -- an oxalate in the juice also inhibits iron absorbtion
  5. Get regular vigorous exercise. Exercise provides the double benefit of improving the heart's fitness and increasing iron excretion.

Sources: personal research notes and various Medline articles

Iron in the Human Body

Approximately 70% of the iron found in the human body is defined as functional. The remainder can be subdivided into transport iron and storage iron. 80% of functional iron can be found in red blood cells, in the compound hemoglobin; the remaining 20% is found in myoglobin and intracellular respiratory enzymes such as cytochromes. 70-80% of storage iron is stored as ferritin in the liver, bone marrow, spleen, and skeletal muscles; a portion of the body's iron is stored instead as hemosiderin. Iron is transported through the bloodstream by the protein transferrin.

The amount of iron in the human body is regulated and balanced by gastrointestinal absorption, which maintains the amount of functional iron and establishes the ferritin and hemosiderin stores. The body's capacity for absorption is affected by the amount of iron that has already been stored, the body's rate of red blood cell production, the amount and kind of iron present in the body's diet, and the amount and kind of enhancer and inhibitor chemicals related to iron absorption present in said diet. Heme iron, present in meat, poultry, and fish, is 2 to 3 times more absorbable than non-heme iron, present in plant-based and iron-fortified foods. Beef liver, clams, oysters, red meats (preferably lean), kidneys, and eggs are all strong sources of heme iron; beans, wheat germ, whole grains, peas, nuts, dried fruits, leafy green vegetables (such as spinach), and of course food which has been fortified are all strong sources of non-heme iron. The chief enhancers for the absorption of non-heme iron are heme iron and vitamin C. Vitamin C can be found in broccoli, tomatoes, sweet potatoes and white potatoes, cantaloupe and citrus fruits. The chief inhibitors for the absorption of both heme and non-heme iron are polyphenols (found in certain vegetables), tannins (found in tea), phytates (found in bran), and calcium (found in dairy products).

The human body recycles iron when it breaks down red blood cells, but it does not retain the iron absolutely. Some (approximately 1 mg) iron gets lost daily in feces, skin cells and mucus, and a miniscule amount is lost through gastrointestinal blood loss. pathological losses of iron can frequently be attributed to sensitivity to cow's milk, peptic ulcer disease, inflammatory bowel disease, bowel cancer, and hookworm infections. Women of child-bearing age lose iron in their menses, averaging out to .3-.5 mg daily in those years. Women lose more iron during and after pregnancy, averaging out to 3 mg daily in that time). It therefore should not be surprising that women of child-bearing age are one of the demographics at highest risk for iron deficiency. Within that demographic category, women with minority ethnic backgrounds and/or who are from lower income brackets are at even higher risk.

SOURCES USED FOR THIS WRITEUP: www.cdc.gov/epo/mmwr/preview/mmwrhtml/00051880.htm, www.goaskalice.columbia.edu/0712.html.

Iron, specifically in the form of its isotope Iron-56, is the most stable nucleus possible, and thus the end point of stellar nucleosynthesis.

The binding energy of a nucleus, what causes the individual protons and neutrons to stick together, is different for different atoms. Using Einstein's formula for relativity, the energy that is no longer needed to tie the nucleons together is released as radiation. As the atoms increase in atomic mass, the energy needed to bind the atom changes its value, along the curve of binding energy. Past iron, adding more nucleons does not produce a more stable nucleus with excess energy, which is why the process ends at iron. And this is how stellar fusion occurs. A star at first burns hydrogen to make helium, and then after some time, in larger stars, to make carbon and heavier elements. An atom of iron-56 is 6% less massive than its component nuuclei, but because of the great difference between matter and energy, that 6% is enough to provide tremendous amounts of energy.

If stars were perfectly efficient engines, there would be a lot more iron in the universe, since it represents the end product of energy formation. However, the energy of activation needed to merge lighter nuclei is quite a bit, and is only available in large, dense, hot stars nearing the very end of their lifespans. Even in these stars, the process is not totally efficient, because as the star goes through its life, especially its final throes, much of its mass is ejected in the form of lighter elements. And when the star does undergo its final collapse, much of the heavier material, including the iron that was built up so painstakingly, is drawn down into the remnant, be it white dwarf, neutron star or black hole. This is a somewhat disappointing move, since that rare iron will not actually be of use by the rest of the universe. And yet, stars are massive things, especially stars that go supernova, so even if only a small percentage of their mass is converted to iron and ejected, it is enough to seed the universe with much iron.

And that is why a good part of the earth's crust and many of the other rocky bodies we can observe are made of iron. Even though iron is a heavy element, and must be made in a series of complicated steps under very extreme conditions, it is the end of the line for stellar nucleosynthesis, and thus is more abundant in the universe than could be guessed. Over time, more iron should appear, and theoretically all of the hydrogen and helium in the universe will be turned to iron. Of course, stars are inefficient, and even in the distant future, there will still be diffuse clouds of lighter gases floating around, but there will definitely be more iron.

And this is the long story of why a common element here on earth, and one that is necessary for our industry and other endeavors, is here because a combination of somewhat mysterious laws of physics, and the efforts of the most extreme stellar furnaces.

Every industry has its own terminology; certain shoe manufacturers and those who repair or modify shoes use the term iron(s) as a way to measure sole thickness. An iron is 1/48th of an inch so a 12 iron sole will measure 1/4 of an inch. Resoling shoes seems to be fading into obscurity which is really too bad since good uppers can usually be resoled saving the wearer money while sparing the landfills. It is estimated that roughly sixty million pairs of shoes are discarded each year and I think it would be interesting to know how many of these could have been resoled. There are some stores that offer recycling programs although these are typically for athletic shoes which are ground up and reincarnated as playground surfacing.

Well made shoes can be resoled multiple times and sometimes even cheaper shoes can be rejuvenated. Your shoes will last longer if you care for them properly, many people who would not wear the same shirt two days in a row will slip their feet into the shoes they wore the day before. The average person puts about two fluid ounces of moisture into their shoes during a typical day which is why your shoes need time to dry after wear. Ideally you should take whatever shoes you wear for extended periods off to give your feet a break. This might mean carrying a pair of shoes to and from work however if it saves your feet and extends the life of your shoes this small burden may pay dividends in your future.

Periodically examining the soles of your shoes for wear and tear will allow you to see which areas are worn. A trained professional can draw some conclusions about the way you walk based on the wear pattern of your shoes. These professionals may be able to resole your shoes using different tread patterns or materials to: increase traction, extend the life of a sole, reduce slippage on wet or oily surfaces, or to reinforce an area that receives excessive abuse, they may even be able to compensate for a structural defect or deformity. Few mortals are perfectly symmetrical however the majority of us do not have noticeable leg length discrepancies. Those who do may be able to get by with an internal heel lift however gross discrepancies will need to be corrected by increasing the sole height of the shoe that corresponds with the shorter limb.

Vanity is an odd disease. Some people would rather walk with a limp or drag their foot behind them than take their shoes in to be modified. Financially challenged patients may not be able to afford modifications and there's always the unforeseen that can't be dealt with. Once shoes are modified you own them unless there was a mistake at the lab. While errors are inevitable regardless of what you do to avoid them I am accustomed to seeing shoe modifications are so flawlessly integrated into the shoe that they can not be detected by casual observation.

As far as I can tell the term iron is used mainly by British and North American companies that work with shoes. That intrigued me since the UK uses the metric system and their shoe sizing system is different from the one used in the United States of America. Europeans have yet another sizing system while Australia tends to follow UK convention. Japan sizes shoes in millimeters which may be a more accurate system if both the length and the girth of each foot are measured. Conversion tables exist however there is no substitute for physically having your foot inside of a particular shoe.

To summarize: one iron is equivalent to 1/48 of an inch. Iron as a unit of measure is a shoe specification used during the manufacturing process and may also be used during repair or modification of a shoe or pair of shoes. Materials for soling and resoling shoes perform differently so knowing the limitations of each medium can help you increase comfort, extend the life of your shoes, and achieve optimum wear from each of your external soles. For additional information on resoling shoes you own please consult your local cobbler or shoe repair shop.

Sites to visit:

I"ron (I"urn), n. [OE. iren, AS. Iren, Isen, Isern; akin to D. ijzer, OS. Isarn, OHG. Isarn, Isan, G. eisen, Icel. Isarn, jArn, Sw. & Dan. jern, and perh. to E. ice; cf. Ir. iarann, W. haiarn, Armor. houarn.]

1. (Chem.)

The most common and most useful metallic element, being of almost universal occurrence, usually in the form of an oxide (as hematite, magnetite, etc.), or a hydrous oxide (as limonite, turgite, etc.). It is reduced on an enormous scale in three principal forms; viz., cast iron, steel, and wrought iron. Iron usually appears dark brown, from oxidation or impurity, but when pure, or on a fresh surface, is a gray or white metal. It is easily oxidized (rusted) by moisture, and is attacked by many corrosive agents. Symbol Fe (Latin Ferrum). Atomic weight 55.9. Specific gravity, pure iron, 7.86; cast iron, 7.1. In magnetic properties, it is superior to all other substances.

⇒ The value of iron is largely due to the facility with which it can be worked. Thus, when heated it is malleable and ductile, and can be easily welded and forged at a high temperature. As cast iron, it is easily fusible; as steel, is very tough, and (when tempered) very hard and elastic. Chemically, iron is grouped with cobalt and nickel. Steel is a variety of iron containing more carbon than wrought iron, but less that cast iron. It is made either from wrought iron, by roasting in a packing of carbon (cementation) or from cast iron, by burning off the impurities in a Bessemer converter (then called Bessemer steel), or directly from the iron ore (as in the Siemens rotatory and generating furnace).


An instrument or utensil made of iron; -- chiefly in composition; as, a flatiron, a smoothing iron, etc.

My young soldier, put up your iron.

3. pl.

Fetters; chains; handcuffs; manacles.

Four of the sufferers were left to rot in irons.


Strength; power; firmness; inflexibility; as, to rule with a rod of iron.

Bar iron. See Wrought iron (below). --
Bog iron, bog ore; limonite. See Bog ore, under Bog. --
Cast iron (Metal.), an impure variety of iron, containing from three to six percent of carbon, part of which is united with a part of the iron, as a carbide, and the rest is uncombined, as graphite. It there is little free carbon, the product is white iron; if much of the carbon has separated as graphite, it is called gray iron. See also Cast iron, in the Vocabulary. --
Fire irons. See under Fire, n. --
Gray irons. See under Fire, n. --
Gray iron. See Cast iron (above). --
It irons (Naut.), said of a sailing vessel, when, in tacking, she comes up head to the wind and will not fill away on either tack. --
Magnetic iron. See Magnetite. --
Malleable iron (Metal.), iron sufficiently pure or soft to be capable of extension under the hammer; also, specif., a kind of iron produced by removing a portion of the carbon or other impurities from cast iron, rendering it less brittle, and to some extent malleable. --
Meteoric iron (Chem.), iron forming a large, and often the chief, ingredient of meteorites. It invariably contains a small amount of nickel and cobalt. Cf. Meteorite. --
Pig iron, the form in which cast iron is made at the blast furnace, being run into molds, called pigs. --
Reduced iron. See under Reduced. --
Specular iron. See Hematite. --
Too many irons in the fire, too many objects requiring the attention at once. --
White iron. See Cast iron (above). --
Wrought iron (Metal.), the purest form of iron commonly known in the arts, containing only about half of one per cent of carbon. It is made either directly from the ore, as in the Catalan forge or bloomery, or by purifying (puddling) cast iron in a reverberatory furnace or refinery. It is tough, malleable, and ductile. When formed into bars, it is called bar iron.


© Webster 1913

I"ron (I"urn), a. [AS. Iren, Isen. See Iron, n.]


Of, or made of iron; consisting of iron; as, an iron bar, dust.


Resembling iron in color; as, iron blackness.


Like iron in hardness, strength, impenetrability, power of endurance, insensibility, etc.; as:


Rude; hard; harsh; severe.

Iron years of wars and dangers.

Jove crushed the nations with an iron rod.


Firm; robust; enduring; as, an iron constitution.


Inflexible; unrelenting; as, an iron will.


Not to be broken; holding or binding fast; tenacious. "Him death's iron sleep oppressed." Philips.

Iron is often used in composition, denoting made of iron, relating to iron, of or with iron; producing iron, etc.; resembling iron, literally or figuratively, in some of its properties or characteristics; as, iron-shod, iron-sheathed, iron-fisted, iron-framed, iron-handed, iron-hearted, iron foundry or iron-foundry.

Iron age.
(a) (Myth.) The age following the golden, silver, and bronze ages, and characterized by a general degeneration of talent and virtue, and of literary excellence. In Roman literature the Iron Age is commonly regarded as beginning after the taking of Rome by the Goths, A. D. 410.
(b) (Archæol.) That stage in the development of any people characterized by the use of iron implements in the place of the more cumbrous stone and bronze. --
Iron cement, a cement for joints, composed of cast-iron borings or filings, sal ammoniac, etc. --
Iron clay (Min.), a yellowish clay containing a large proportion of an ore of iron. --
Iron cross, a Prussian order of military merit; also, the decoration of the order. --
Iron crown, a golden crown set with jewels, belonging originally to the Lombard kings, and indicating the dominion of Italy. It was so called from containing a circle said to have been forged from one of the nails in the cross of Christ. --
Iron flint (Min.), an opaque, flintlike, ferruginous variety of quartz. --
Iron founder, a maker of iron castings. --
Iron foundry, the place where iron castings are made. - - Iron furnace, a furnace for reducing iron from the ore, or for melting iron for castings, etc.; a forge; a reverberatory; a bloomery. --
Iron glance (Min.), hematite. --
Iron hat, a headpiece of iron or steel, shaped like a hat with a broad brim, and used as armor during the Middle Ages. --
Iron horse, a locomotive engine. [Colloq.] --
Iron liquor, a solution of an iron salt, used as a mordant by dyers. --
Iron man (Cotton Manuf.), a name for the self-acting spinning mule. --
Iron mold or mould, a yellow spot on cloth stained by rusty iron. --
Iron ore (Min.), any native compound of iron from which the metal may be profitably extracted. The principal ores are magnetite, hematite, siderite, limonite, Göthite, turgite, and the bog and clay iron ores. --
Iron pyrites (Min.), common pyrites, or pyrite. See Pyrites. --
Iron sand, an iron ore in grains, usually the magnetic iron ore, formerly used to sand paper after writing. --
Iron scale, the thin film which forms on the surface of wrought iron in the process of forging. It consists essentially of the magnetic oxide of iron, Fe3O4. --
Iron works, a furnace where iron is smelted, or a forge, rolling mill, or foundry, where it is made into heavy work, such as shafting, rails, cannon, merchant bar, etc.


© Webster 1913

I"ron, v. t. [imp. & p. p. Ironed (?); p. pr. & vb. n. Ironing.]


To smooth with an instrument of iron; especially, to smooth, as cloth, with a heated flatiron; -- sometimes used with out.


To shackle with irons; to fetter or handcuff. "Ironed like a malefactor." Sir W. Scott.


To furnish or arm with iron; as, to iron a wagon.


© Webster 1913

I"ron (I"urn), n. (Golf)

An iron-headed club with a deep face, chiefly used in making approaches, lifting a ball over hazards, etc.


© Webster 1913

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