IRMIN

irmin, or irminus, in teutonic mythology, a deified eponymic hero of the herminones. the chief seat of his worship was irminsal, or ermensul, in westphalia, destroyed in 772 by charlemagne. huge wooden posts (irmin pillars) were raised to his honour, and were regarded as sacred by the saxons. irnerius (hirnerius, hyrnerius, iernerius, gernerius, guarnerius, warnerius, wernerius, yrnerius), italian jurist, sometimes referred to as "lucerna juris." he taught the "free arts" at bologna, his native city, during the earlier decades of the 12th century. of his personal history nothing is known, except that it was at the instance of the countess matilda, hildebrand's friend, who died in 1115, that he directed his attention and that of his students to the _institutes_ and _code_ of justinian; that after 1116 he appears to have held some office under the emperor henry v.; and that he died, perhaps during the reign of the emperor lothair ii., but certainly before 1140. he was the first of the glossators (see gloss), and according to ancient opinion (which, however, has been much controverted) was the author of the epitome of the _novellae_ of justinian, called the _authentica_, arranged according to the titles of the _code_. his _formularium tabellionum_ (a directory for notaries) and _quaestiones_ (a book of decisions) are no longer extant. (see roman law.) see savigny, _gesch. d. rom. rechts im mittelalter_, iii. 83; vecchio, _notizie di irnerio e della sua scuola_ (pisa, 1869); ficker, _forsch, z. reichs- u. rechtsgesch. italiens_, vol. iii. (innsbruck, 1870); and fitting, _die anfange der rechtsschule zu bologna_ (berlin, 1888). iron [symbol fe, atomic weight 55.85 (o = 16)], a metallic chemical element. although iron occurs only sparingly in the free state, the abundance of ores from which it may be readily obtained led to its application in the arts at a very remote period. it is generally agreed, however, that the iron age, the period of civilization during which this metal played an all-important part, succeeded the ages of copper and bronze, notwithstanding the fact that the extraction of these metals required greater metallurgical skill. the assyrians and egyptians made considerable use of the metal; and in genesis iv. 22 mention is made of tubal-cain as the instructor of workers in iron and copper. the earlier sources of the ores appear to have been in india; the greeks, however, obtained it from the chalybes, who dwelt on the south coast of the black sea; and the romans, besides drawing from these deposits, also exploited spain, elba and the province of noricum. (see metal-work.) the chief occurrences of metallic iron are as minute spiculae disseminated through basaltic rocks, as at giant's causeway and in the auvergne, and, more particularly, in meteorites (q.v.). in combination it occurs, usually in small quantity, in most natural waters, in plants, and as a necessary constituent of blood. the economic sources are treated under iron and steel below; in the same place will be found accounts of the manufacture, properties, and uses of the metal, the present article being confined to its chemistry. the principal iron ores are the oxides and carbonates, and these readily yield the metal by smelting with carbon. the metal so obtained invariably contains a certain amount of carbon, free or combined, and the proportion and condition regulate the properties of the metal, giving origin to the three important varieties: cast iron, steel, wrought iron. the perfectly pure metal may be prepared by heating the oxide or oxalate in a current of hydrogen; when obtained at a low temperature it is a black powder which oxidizes in air with incandescence; produced at higher temperatures the metal is not pyrophoric. peligot obtained it as minute tetragonal octahedra and cubes by reducing ferrous chloride in hydrogen. it may be obtained electrolytically from solutions of ferrous and magnesium sulphates and sodium bicarbonate, a wrought iron anode and a rotating cathode of copper, thinly silvered and iodized, being employed (s. maximowitsch, _zeit. elektrochem._, 1905, 11, p. 52). in bulk, the metal has a silvery white lustre and takes a high polish. its specific gravity is 7.84; and the average specific heat over the range 15 deg.-100 deg. is 0.10983; this value increases with temperature to 850 deg., and then begins to diminish. it is the most tenacious of all the ductile metals at ordinary temperatures with the exception of cobalt and nickel; it becomes brittle, however, at the temperature of liquid air. it softens at a red heat, and may be readily welded at a white heat; above this point it becomes brittle. it fuses at about 1550 deg.-1600 deg., and may be distilled in the electric furnace (h. moissan, _compt. rend._, 1906, 142, p. 425). it is attracted by a magnet and may be magnetized, but the magnetization is quickly lost. the variation of physical properties which attends iron on heating has led to the view that the metal exists in allotropic forms (see iron and