Iron is an excellent and versatile material of construction--strong, tough, easily formed and worked, and, very importantly, cheap compared to the alternatives. Plastics give it competition, especially in products that must be manufactured at the lowest cost where strength and durability are not the primary concerns, such as modern American automobiles. Aluminium is a strong competitor where weight is a concern, as in aircraft. However, the versatility of iron-carbon alloys cannot be matched in any other material. Alloys with other metals, such as nickel, chromium and manganese, give further advantages. These steels can be tailored to nearly every demand, and are not significantly challenged as materials of construction.The shortcomings of iron are its weight, and its propensity to rust. Both aluminium and plastics avoid these shortcomings, because their densities are much less than that of iron, and aluminium is protected by an adherent layer of oxide, and plastics by the inertness of the substance. The advantages of iron are so great, however, that these considerations prevail only in limited fields of application.The three metals iron, cobalt and nickel are called the "iron family" and are very similar, so I shall discuss them together. A property of the iron family for which there is no substitute at an equivalent cost is that they can be induced to provide a strong magnetic field with only small excitation by an electric current. It is a very remarkable property, so an effort will be made to explain how it arises, and how it is used. Also, iron is important as a carrier of oxygen in blood, and how it does this will be explained.In addition to these subjects, the physical and chemical properties of iron will be reviewed, and its curiosities examined, as usual. For some accounts and explanations, reference will be made to other articles where they appear, and will not be duplicated here. This is especially true of the application of iron as an engineering material, a very extensive subject.Our word iron is cognate to the German Eisen, which in various forms is found in all the northern European languages, though not elsewhere. Why our pronunciation of the word is metathetical, "iorn" instead of "iron," I have not heard. In Gothic, it was eisarn, and in Old High German, isan. In Greek, iron is síderos and steel is chalybicón, stems that are encountered frequently in talking of iron, as in "siderurgy" and "chalybeate spring." "Sidereal time" is not iron time, however, but the "sider-" comes from the similar Latin sidera, "stars." Iron was very valuable when it came to the bronze-age Greeks from its inventors around the Pontus Euxinus, and was used for jewellery and prizes. It has been money in other places and times. The Latin for iron is ferrum, from which the word in most European languages has been derived, and which appears more commonly than any other stem in words dealing with iron, especially in chemical nomenclature.
Cobalt is from Kobold, an earth spirit, or a good house spirit. The kobold came surreptitiously and stole the silver from the ore, replacing it with base cobalt. There is a Greek word kobalos, meaning "rogue, trickster," but there is probably no connection with the German. Nickel is from Nickel, a water spirit, who took the copper from the ore and washed it away, replacing it with kupfernickel. A Nix is a male water spirit, a Nixe a female water spirit. These names were from miner's slang, not traditional names for the metals, which were unknown at the time. Many minerals resemble ores, but do not yield the expected metal, and this was confusing when their chemical natures were not known. Cobalt was recognized by Brandt in 1735 and nickel by Cronstadt in 1750, but their compounds were not carefully studied until the next century.
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