IHNEHIUS, or GARNIA, b. Italy, llth c.; was professor of Roman law in the uni versity of Bologna, . IRON (sym. Fe [Laa. ferrum], eq. 28—in the new system, 56—sp. gr. 7,844) occurs more abundantly than any other metal. In its native form it is chiefly found in meteoric stones (see AEB4OLITES), and in certain ores of platinum, and is consequently of compar atively rare occurrence, but the so-called iron ores—the oxides, sulphides, etc.—are very widely distributed. The most important of these ores are mentioned below.
Pure iron may be obtained by the ordinary method described below, and also by reducing the peroxide by means of hydrogen gas and heat, when it is obtained in the form of a fine black powder, or by hosting the protochloride in a glass tube through which a current of dry hydrogen is passed. In this ease, pure iron is deposited as a glis tening mirror on the glass.
This important metal will be most conveniently considered under the three heads of 1. Chemistry of pure iron is of so little general interest that we shall confine our remarks on the properties of this metal to those which are exhibited by liar or wrought iron. Its color is gray or bluish-white; it is hard and lustrous, takes a high polish, is fibrous in texture, and' when broken across, exhibits a ragged fracture. It requires a very intense heat for its fusion, but before inching passes into a soft pasty condition, in which state two pieces of iron may, by being hammered together, be united or welded so completely as to form, to all intents and purposes, a single portion. At a red heat, it may be readily forged into any shape; but at ordinary temperatures it pos sesses very little malleability, as compared with gold and silver. In ductility, it stands very high, being barely exceeded by gold, silver, and platinum; and in tenacity, it is only exceeded by cobalt and nickel. Its susceptibility to magnetism is one of its most remarkable characteristics. See MAGNETISM. At a high temperature, it burns readily, as may be seen at the forge, or (more strikingly) when a glowing wil.e is introduced into
a jar of oxygen, In dry air, and at ordinary temperatures, the lustrous surface of the metal remains unchanged; but in a moist atmosphere the surface rapidly becomes oxi dized and covered with rust, which consists mainly of the hydrated o-xide of iron. At a red heat, iron decomposes water, and liberates hydrogen, the oxygen combining with the iron to form the black or magnetic oxide which occurs in minute crystals. This is one of the ordinary methods of obtaining hydrogen.
The affinities of iron for most of the non-metallic elements are very powerful. The chief of the iron compounds are a. Oxides of forms four definite compounds with oxygen—viz. (1), the protoxide (Fe0). which is the base of the green or ferroussalts of iron ; (2), the sesguioxide or peroxide which is the base of the red or ferric salts; (3), the black or magnetic oxide which is regarded by some chemists as a compound of the two preceding oxides; and (4), ferric acid The protoxide cannot be obtained in an isolated form, but it forms the base of various ferroti salts, and combines with water to form a hydrate (FeO,HO), which, on the addition of an alkali, falls in white flakes.
The most important protosalts of iron, or ferrous salts, are the carbonate, the .sul phate, the phosphate, and the silicate.
Carbonate of iron naturally in various minerals, and may be obtained artificially by precipitating a soluble protosalt of iron with carbonate of potash or soda, when the carbonate falls in white flakes, On exposure to the air, it absorbs oxygen, and gives off carbonic acid, and is thus converted into the hydrated peroxide. Sulphate of iron is obtained by the solution of iron, or its sulphide, in dilute sul phuric acid; in the former case, there is an evolution of hydrogen, and in the latter, of sulphureted hydrogen. The reactions in the two cases are expressed by. the equations, Fe + = Fe0, FeS+ S02,H0 = + HS.