* 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).

My young soldier, put up your iron. Shak.

Four of the sufferers were left to rot in irons. Macaulay.

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.

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