Iron

See also Iron & Steelmaking and Steel Alloys.

Introduction

Iron is the cheapest, most abundant and most useful of all metals.   It is used extensively to construct tools, fasteners, machinery, vehicles, bridges, buildings, and appliances.   Iron is ductile, malleable, machinable, and takes a high polish.   It can be melted and cast into forms and it can welded when hot.   Iron is used as a catalyst in the Haber Process for making ammonia.   Steel is an alloy of iron, carbon, and small amounts of other elements to make it stronger than iron.   Like iron, steel also is of ancient, unknown origin and was used to make simple drilling, digging and cutting tools in ancient Asian and North African cities.   The famous Toledo and Damascus sword blades of the Middle Ages were made of steel by hand, which made them very expensive.   Iron contains (usually) undesirable elements such as silicon, phosphorus, sulfur, and manganese.   In steel these impurities removed and replaced by more desirable elements, called steel alloys to impart special properties for special uses.

Iron is essential to life.   In animals, it is the central atom in the hemoglobin molecule in blood and myoglobin in muscles that supply oxygen to cells.   Iron is a part of several enzymes and proteins.   Sources: liver, kidneys, red meats, egg yolk, green, leafy vegetables, dried fruits, dried beans and peas, potatoes, blackstrap molasses, enriched and whole-grain cereals.   Iron from animal sources is more easily absorbed by humans than that obtained from vegetables.   Excessive intake of coffee and tea can reduce iron absorption.   An iron deficiency results in anemia with accompanying fatigue, weakness, pallor and shortness of breadth. ^{Brody 186}, ^{Netzer 801}   Iron deficiencies in humans usually is associated with excessive loss of blood, such as with menstruation, hemorrhoids, and ulcers.   Bone marrow malfunctioning can also cause an iron deficiency.

In plants, iron is necessary for many enzymes used for the synthesis of chlorophyll.   It is essential for the young, growing parts of plants.   Deficiencies are pale leaf color of young leaves followed by yellowing of leaves and large veins.   Iron is lost by leaching and occurs in the lower portions of the soil structure.   Under conditions of high pH (alkaline) iron is rendered unavailable to plants, although it may be abundant. ^{Morgan n.p.}

Grazing animals seldom suffer from iron deficiencies, since they are able to obtain sufficient iron from their meadow food.   However, grazing animals on alkaline and sandy soils, where the iron content is minimal, are vulnerable to iron deficiencies.   One remedy is to add a soluble iron compound to the soil or spray plant foliage with it.   Soils can be made more acid by adding sulfur and manure to improve its iron content.   Young pigs raised in confinement on concrete floors where they cannot obtain iron available in meadows often suffer from iron deficiency.   The solution is to inject them with iron compounds or paint the sow's udder with iron compounds that are then ingested by the piglets. ^{Considine 1664-1666}

Iron is found combined chemically with other elements and a mixture of other materials in an aggregate called iron ore.   In the earlier years of the U. S., enough iron ore could be found in most parts of the country to operate blast furnaces.   However, as the need for steel grew, larger iron ore deposits were needed.   The Marquette iron range on Michigan's Upper Peninsula, one of the largest concentrations of iron ore in the U.S., was discovered in 1844.   It furnished a plentiful supply of iron ore to the iron mills around the Great Lakes and the upper Ohio, Monongohela, and Allegheny Rivers.   Later, Minnesota became famous for its vast quantities of iron ore, e.g., the Mesabi and Vermillion Ranges.   Large deposits in Quebec & Labrador was also used by American and European steelmakers.   Iron is the fourth most abundant element making up the earth's crust.   Common ores are hematite, Fe₂O₃, and magnetite, Fe₃O₄, which is highly magnetic.   Other ores are ilmenite, FeTiO₃, limonite, HFeO₂ and FeO(OH), and siderite, FeCO₃.   Iron also occurs as sulfides, like pyrite, FeS₂ and FeS, which are more useful as sources of sulfur (S) and other metals associated with iron sulfides.   Iron ores are mined at the earth's surface and underground.   Iron ore can percolate to the top of marsh bogs, which were cheap iron ore sources in early America, when digging tools were simple and easily dulled with use.   Because iron readily combines chemically with other elements to form compounds, it is rarely found in pure form.   Iron oxides ("rust") damage iron when exposed to moist air.   Pure iron is attracted by magnets, but does not retain much of its magnetism after the magnet is removed.