| | | | | producers of iron from ore in the world are China, |
| The period in human history beginning in about 1200 | | | | Japan, the United States, Russia, Germany, and Brazil. |
| B.C. is called the Iron Age as it was at about this time | | | | Iron is one of only three naturally occurring magnetic |
| that humans first learned how to use iron metal. But in | | | | elements. |
| some ways, one could refer to the current era as the | | | | There are four naturally occurring isotopes of iron, |
| New Iron Age as iron is probably the most widely used | | | | iron-54, iron-56, iron-57, and iron-58. Six radioactive |
| and most important metal today. No other metal is | | | | isotopes of iron are known also. Two radioactive |
| available to replace iron in all its many applications. Iron | | | | isotopes of iron are used in medical and scientific |
| is a transition metal. The transition metals are typical | | | | research. They are iron-55 and iron-59. These isotopes |
| metals in that they tend to be bright, shiny, silvery solids. | | | | are used primarily as tracers in studies on blood. A |
| They all tend to conduct heat and electricity well. And | | | | tracer is a radioactive isotope whose presence in a |
| they usually have high melting points. | | | | system can easily be detected. The isotope is injected |
| Iron normally does not occur as a free element in the | | | | into the system. Inside the system, the isotope gives |
| earth. In fact, iron was not of much value to humans | | | | off radiation. That radiation can be followed by |
| until they learned how to free iron from its compounds. | | | | detectors placed around the system. Iron-55 and |
| Once they could do that, humans were able to make | | | | iron-59 are used to study the way in which red blood |
| tools, weapons, household implements, and other | | | | cells develop in the body. These studies can be used |
| objects out of iron. This step marked the beginning of | | | | to tell if a person's blood is healthy. |
| the Iron Age. Some meteorites are very rich in iron. | | | | Iron goes through a number of stages between ore |
| Iron is most valuable not as a pure metal, but in alloys. | | | | and final steel product. In the first stage, iron ore is |
| An alloy is made by melting and mixing two or more | | | | heated with limestone and coke (pure carbon) in a |
| metals. The mixture has properties different from | | | | blast furnace. A blast furnace is a very large oven in |
| those of the individual metals. The best known and | | | | which the temperature may reach 1,500°C |
| most widely used alloy of iron is steel which contains | | | | (2,700°F). In the blast furnace, coke removes oxygen |
| iron and at least one other element. Today, specialized | | | | from iron ore. The limestone removes impurities in the |
| steels of all kinds are available for many different | | | | iron ore. Iron produced by this method is about 91 to 92 |
| applications. | | | | percent pure. The main impurity left is carbon from the |
| Ancient Egyptians had learned how to use iron before | | | | coke used in the furnace. This form of iron is known |
| the First Dynasty, which began in about 3400 B.C. The | | | | as pig iron. Pig iron is generally too brittle (it breaks too |
| Egyptians probably found the iron in meteorites. | | | | easily) to be used in most products. Most scientists |
| Meteorites are chunks of rock and metal that fall from | | | | believe that the Earth's core consists largely of iron. |
| the sky. Some meteorites are very rich in iron. The | | | | A number of methods have been developed for |
| Egyptians made tools and jewelry out of iron. Iron is | | | | purifying pig iron. A common method used today is |
| probably the most widely used and most important | | | | called the basic oxygen process. In this process, pig |
| metal today. Iron was also known to early Asian | | | | iron is melted in a large oven. Then pure oxygen gas is |
| civilizations. In Delhi, India, for example, a pillar made out | | | | blown through the molten pig iron. The oxygen burns |
| of iron built in A.D. 415 still stands. It weighs 6.5 metric | | | | off much of the carbon in the pig iron. Although now |
| tons and remains in good condition after nearly 1,600 | | | | outdated, iron stoves were once the primary source |
| years. | | | | of heat for homes, as well as a means for cooking. A |
| Early Chinese civilizations also knew about iron. | | | | small amount of carbon remains in the iron. The iron |
| Workers learned to produce iron as early as 200 B.C. | | | | produced in this reaction is known as steel. |
| A number of iron objects, including cannons, remain | | | | The term "steel" actually refers to a wide variety of |
| from the Han period (202 B.C. to A.D. 221). The Bible | | | | products. The various forms of steel all contain iron |
| also includes many mentions of iron. For example, a | | | | and carbon. They also contain one or more other |
| long passage in the book of Job describes the mining | | | | elements, such as silicon, titanium, vanadium, chromium, |
| of iron. Other passages tell about the processing of | | | | manganese, cobalt, nickel, zirconium, molybdenum, and |
| iron ore to obtain iron metal. By the time of the Roman | | | | tungsten. Two other steel-like products are cast iron |
| civilization, iron had become an essential metal. The | | | | and wrought iron. Cast iron is an alloy of iron, carbon, |
| historian Pliny (A.D. 23-79) described the role of iron in | | | | and silicon. Wrought iron contains iron and any one or |
| Rome: | | | | more of many other elements. In general, however, |
| It is by the aid of iron that we construct houses, cleave | | | | wrought iron tends to contain very little carbon. |
| rocks, and perform so many other useful offices of | | | | It would be impossible to list all uses of iron and steel |
| life. But it is with iron also that wars, murders, and | | | | products. In general, those products can be classified |
| robberies are effected, and this, not only hand to hand, | | | | into categories: (1) automotive; (2) construction; (3) |
| but from a distance even, by the aid of weapons and | | | | containers, packaging, and shipping; (4) machinery and |
| winged weapons, now launched from engines, now | | | | industrial equipment; (5) rail transportation; (6) oil and gas |
| hurled by the human arm, and now furnished with | | | | industries; (7) electrical equipment; and (8) appliances |
| feathery wings. Even from the earliest days, humans | | | | and utensils. Some iron is made into compounds. The |
| probably seldom used iron in a pure form. It was | | | | amount is very small compared to the amount used in |
| difficult to make iron that was free of impurities, such | | | | steel and other iron alloys. Probably the fastest |
| as carbon (charcoal) and other metals. More important, | | | | growing use of iron compounds is in water treatment |
| however, it became obvious that iron with impurities | | | | systems. The terms ferric and ferrous refer to two |
| was a stronger metal that iron without impurities. | | | | different forms in which iron occurs in compounds. |
| It was not until 1786, however, that scientists learned | | | | Some of the important iron compounds are. |
| what it was in steel that made it a more useful metal | | | | Uses of some of the compounds of iron may be |
| than iron. Three researchers, Gaspard Monge | | | | mentioned as: ferric acetate is used in the dyeing of |
| (1746-1818), C. A. Vandermonde, and Claude Louis | | | | cloth; ferric ammonium oxalate is used in blueprints, |
| Berthollet (1748-1822) solved the puzzLe. They found | | | | ferric arsenate is an insecticide, ferric chloride is used in |
| that a small amount of carbon mixed with iron | | | | water purification and sewage treatment systems, |
| produced a strong alloy. That alloy was steel. Today, | | | | dyeing of cloth, coloring agent in paints, additive for |
| the vast amount of iron used in so many applications is | | | | animal feed, etching material for engraving, |
| used in the form of steel, not pure iron. Ancient | | | | photography, and printed circuits; ferric chromate is |
| Egyptians had learned how to use iron before the First | | | | used as yellow pigment (coloring) for paints and |
| Dynasty, which began in about 3400 B.C. The chemical | | | | ceramics, ferric hydroxide is brown pigment for |
| symbol for iron is Fe. That symbol comes from the | | | | coloring rubber and use in water purification systems; |
| Latin name for iron, ferrum. | | | | ferric phosphate is fertilizer; additive for animal and |
| Iron is a silvery-white or grayish metal. It is ductile and | | | | human foods, ferrous acetate is used in dyeing of |
| malleable. It is one of only three naturally occurring | | | | fabrics and leather besides being wood preservative; |
| magnetic elements. The other two are nickel and | | | | ferrous gluconate is used as a dietary supplement in |
| cobalt. Iron has a very high tensile strength. Iron is also | | | | "iron pills; ferrous oxalate is yellow pigment for paints, |
| very workable. Workability is the ability to bend, roll, | | | | plastics, glass, and ceramics, and photographic |
| hammer, cut, shape, form, and otherwise work with a | | | | developer; ferrous sulfate is used in water purification |
| metal to get it into a desired shape or thickness. The | | | | and sewage treatment systems; catalyst in production |
| melting point of pure iron is 1,536°C (2,797°F) and its | | | | of ammonia; fertilizer; herbicide; additive for animal feed; |
| boiling point is about 3,000°C (5,400°F). Its density is | | | | wood preservative; additive to flour to increase iron |
| 7.87 grams per cubic centimeter. The melting point, | | | | levels. |
| boiling point, and other physical properties of steel | | | | Iron is of critical importance to plants, humans, and |
| alloys may be quite different from those of pure iron. | | | | animals. It occurs in hemoglobin, a molecule that carries |
| Iron is a very active metal. It readily combines with | | | | oxygen in the blood. Hemoglobin picks up oxygen in |
| oxygen in moist air. The product of this reaction, iron | | | | the lungs, and carries it to the cells. In the cells, oxygen |
| oxide (Fe2O3), is known as rust. Iron also reacts with | | | | is used to produce energy the body needs to survive, |
| very hot water and steam to produce hydrogen gas. It | | | | grow, and stay healthy. The U.S. Recommended Daily |
| also dissolves in most acids and reacts with many | | | | Allowance (USRDA) for iron is 18 milligrams. The |
| other elements. Iron is the fourth most abundant | | | | USRDA is the amount of an element that a person |
| element in the Earth's crust. Its abundance is estimated | | | | needs to stay healthy. Iron is available in a number of |
| to be about 5 percent. Most scientists believe that the | | | | foods, including meat, eggs, and raisins. |
| Earth's core consists largely of iron. Iron is also found in | | | | An iron deficiency (lack of iron) can cause serious |
| the Sun, asteroids, and stars outside the solar system. | | | | health problems in humans. For instance, hemoglobin |
| The most common ores of iron are hematite, or ferric | | | | molecules may not form in sufficient numbers. Or they |
| oxide (Fe2O3); limonite, or ferric oxide (Fe2O3); | | | | may lose the ability to carry oxygen. If this occurs, a |
| magnetite, or iron oxide (Fe3O4); and siderite, or iron | | | | person develops a condition known as anemia. |
| carbonate (FeCO3). An increasingly important source | | | | Anemia results in fatigue. Severe anemia can result in |
| of iron is taconite. Taconite is a mixture of hematite | | | | a lowered resistance to disease and an increase in |
| and silica (sand). It contains about 25 percent iron. The | | | | heart and respiratory (breathing) problems. Some |
| largest iron resources in the world are in China, Russia, | | | | forms of anemia can even cause death. |
| Brazil, Canada, Australia, and India and the largest | | | | |