Page:The American Cyclopædia (1879) Volume IX.djvu/379

 IRON 365 contains Lake Baikal. It is rich in minerals, among which are gold, silver, copper, and iron. Extensive forests, furnishing excellent timber, and abounding in all kinds of game, occupy a large portion of the country; and agriculture is prosperously conducted, barley and rye be- ing the principal crops. The pastures support great numbers of cattle and sheep. The sum- mers are short, but very warm and generally clear, while the winters are so cold that some- times mercury freezes. A considerable portion of the inhabitants are descendants of Russian exiles, and the majority of the natives are Mongols, Tunguses, and Buriats. II. A city, capital of the government and of E. Siberia, on the right bank of the Lower Angara, about 35 m. from its source in Lake Baikal ; pop. about 30,000. It lies on both sides of the mouth of the Ushakovka, a small tributary of the Angara, and opposite the confluence of the Irkut with the latter river. It is well built, paved, and lighted. The principal streets run parallel with the Angara, on the banks of which are the exchange, the admiralty offices and dockyards, the governor general's palace, and various government factories and work- shops in which convicts are employed. In the centre of the city is a handsome public square, on which front the houses of many of the func- tionaries, and the guard house. The school of medicine, the gymnasium, and the former depot of the Russian American company are fine and spacious. There are many public schools, a high school for navigation, a female orphan school, a theatre, and a good bazaar. The city is fortified, and has a citadel. It con- tains 15 churches, and numerous convents and hospitals, and is the see of an archbishop. Nearly all the houses are of wood, neatly planked, and painted yellow or gray. The principal manufactures are woollens, linens, leather, glass, and soap. The trade of Irkutsk is important. It is the great commercial en- trepot between the Chinese empire and Euro- pean Russia, exporting to the latter tea, rhu- barb, fruits, porcelain, paper, silk, &c., in ex- change for furs, metals, and various European goods. It has a great fair in June. IRON, one of the elementary substances, pos- sessing when pure the following characters: specific gravity, 8-1393 (Percy) ; hardness, 4-5 ; crystalline form, isometric ; color, silver-gray ; lustre, metallic ; atomic weight, 56 (O = 16) ; specific heat, 0-113795. Its symbol is Fe (fer- rum). Although seldom found native, and never pure, iron is the most universally and extensively distributed of metals. It occurs in large deposits in the form of oxide, and constitutes an ingredient of nearly all rocks, soils, and natural waters. So-called chalybeate mineral springs contain it in relatively large amounts. As a consequence of this wide distri- bution in the inorganic world, it is found also in vegetable and animal organisms, constituting 0-07 per cent, of the blood, or 5-5 to 8-5 per cent, of the ash of blood. Pure iron is un- known in the arts ; and, owing to the difficulty of procuring it on a large scale, its properties have been but slightly investigated. Peligot states that iron prepared by the reduction of its protochloride by hydrogen, is filamentous, compact, malleable, and almost as white as sil- ver. Iron deposited by the galvanic battery is grayish white and susceptible of a high polish ; it is scarcely attacked by sulphuric or muriatic acid at ordinary temperatures, but is dissolved on application of heat, evolving hydrogen free from fetid odor (in contradistinction from manufactured iron). Its malleability is not af- fected by rapid cooling after exposure to a high temperature. Iron may be rendered strongly magnetic by induction, but loses its magnetic power, when pure, as soon as the source of magnetism is removed. Throughout a wide range of temperature, from red heat to near its melting point, iron is more or less plastic. At red heat it is readily forged under the hammer, and at white heat two masses of iron can be firmly and intimately incorporated with each other (welded) by hammering or pressure. Welding, though not exclusively a property of iron, is possessed by no other metal to so great a degree. It is volatilized in the heat of the voltaic arch. Iron is a metal of active chemi- cal affinities, and enters into a large number of compounds. It combines with oxygen in four proportions, as follows : COMPOUNDS WITH OXYGEN. For- mula. Iron, per c't. <).vy u -,Tl per c't. Ferrous oxide (protoxide of iron). . . FeO TT-TT 22 '28 Ferric oxide (scsquioxide of iron) Ferroso-ferric oxide (protosesquioxide 1 of iron ; magnetic oxide) f Fe a 03 Fe 3 0, 70-00 72-41 30-00 21-09 Ferric acid FeO, 53-80 46-20 Metallic iron rusts when exposed to moist air, and is gradually and completely converted into oxide. Mr. Grace Calvert, investigating the conditions necessary or favorable to the rust- ing of iron, has found that it is not acted upon by pure, dry oxygen or carbonic acid, while it is feebly attacked by moist oxygen or carbonic acid, and most rapidly by moist oxygen con- taining traces of carbonic acid, which forms first oxide, then ferrous carbonate, and finally hydrated sesquioxide, with admixtures of fer- rous oxide and carbonate. Carbonic acid and water likewise act with energy. Solutions of alkaline hydrates, carbonates, or bicarbonates prevent the rusting of iron, while a solution of sugar promotes it. The oxidation of iron may be hindered by attaching it to a more electro-positive metal, such as zinc, or promo- ted by the presence of a more electro-negative metal, such as copper. Under ordinary cir- cumstances zinc will protect iron when it cov- ers only -jfa of the surface of the latter, but in a solution of sugar the proportion of sur- face covered by zinc must be 1 to 15. * The fol- lowing analysis by Grace Calvert gives the composition of rust from Llangollen, Wales :