IRITIS-IRON.

Kingdom. Between the coasts of Louth and Lancaster, the I. S. has a width of 120 miles; its greatest length between St George's Channel on the south and the North Channel on the north is also about 120 miles.

enjoys a very healthy climate, though in winter the cold is so severe as to freeze mercury. The streets are straight and wide, but ill-paved, and the houses mostly built of timber. The best buildings are the palace of the governor-general, IRITIS is the term applied to inflammation of American Company. Besides these, the town conthe schools for boys and girls, and the hall of the the Iris. See EYE. The cavity across which the tains a public library, a museum of natural history, iris is stretched, and the iris itself, which projects and some other public institutions. The population into that cavity, and divides it into an anterior and in 1858 was 18,908, consisting mostly of Russians a posterior chamber, are lined or invested by a and Buriats. I. was founded in 1661 by a Cossack membrane which resembles the larger serous mem- chief named Iwan Pochapof, and, owing to its posi branes of the body, such as the pleura, peritoneum,tion on the great thoroughfare between Eastern and &c., and consequently the inflammation of this membrane is of the adhesive kind. See INFLAMWhen it is added that the effusion of lymph may limit or entirely stop the movements of the iris, and may alter the form, or even close up the aperture of the pupil, the serious nature of the disease will be at once perceived.

MATION.

Baikal.

The communications between I. and

Western Siberia, between China and Russia, it soon for the tea-trade. The current of the Angara is so became the commercial centre of Siberia, especially with ice. Nevertheless, it is navigable, and constirapid that the strongest frosts cover it but seldom tutes the mainway for the goods bound for Kiachta by means of Lake Baikal, as well as for those The objective symptoms of iritis (those which can be observed by the physician) are: 1. Redness of China to Irkutsk. The former are chiefly furs and coming from Eastern Siberia, Russian America, and the eye, arising from vascularity of the sclerotic; 2. Change in the colour of the iris. When lymph metals; the latter, tea, meat, and fish from Lake is effused in the texture of the iris, a gray or blue Jakutsk, and the other northern towns of Siberia, are eye is rendered yellowish or greenish, while in a carried on by the river Lena. The manufactures dark eye a reddish tint is produced. The brilliancy of the colour of the iris also disappears. When the of I. are purely local, and supply the half-nomad inflammation is very violent, or has been unchecked Buriats and Tunguses, inhabiting the adjacent by remedies, suppuration may take place. 3. Irregularity, and sometimes immobility of the pupil, produced by the adhesion of the back of the iris to the crystalline lens. The subjective symptoms (those of which the patient alone is conscious) are intolerance of light, dimness of vision, and pain in and around the eye.

The causes of iritis are various. The disease may arise from actual injury in surgical operations performed on the eye; from over-exertion, and too prolonged continuous use of the eye (thus, it is common among needlewomen, engravers, and watchmakers); or from some constitutional taint, especially syphilis, gout, rheumatism, and scrofula. The treatment of iritis varies to some extent according to the cause which induces it, but the great remedies are three. 1. Blood-letting, for the purpose of moderating the febrile disturbance, and of facilitating the operation of the second remedy, which is, 2. Mercury, which used to be given in large doses (such as two, three, or four grains, with a little opium, every four or six hours), but which is preferably given in small doses, such as two or three grains of hydrarg. c. cretâ, with a little hyoscyamus, two or three times in the twenty-four hours. This dose should be lessened as soon as the mouth begins to be tender, and by that time the lymph will be found to break up, and leave the pupil clear. 3. Belladonna. The pupil should be kept well dilated by the application of the extract of belladonna to the skin round the eye, or, far better, by the instillation into the eye of a weak solution of sulphate of atropine, with the view of preventing adhesion of the iris, or of breaking, or, at all events, of stretching and elongating any adhesive bands that may be formed; and thus of preventing any impairment of the movements of the iris, and any irregularity of the pupil, after the inflammation shall have abated.

country.

The

IRKUTSK, a government of Eastern Siberia, bounded by the government of Jenisseisk, the province of Jakutsk and the Chinese Empire, occupies an area of 267,555 square miles. soil is partly fertile, partly hilly and marshy; the climate in general severe. The Baikal and Nerchinsk Mountains, with their numerous branches, give the country a high alpine character; besides these, the Saian range extends along the southern borders, and the Jablonovy or Apple range along the eastern. The principal rivers are the Lena, Shilka, Agún; the largest lake is the Baikal (q. v.). The productions of the country are rye, wheat, barley, oats, rhubarb, hops; reindeer, sables, ermines, foxes, seals; fish-sturgeon, cod, silure; minerals-gold, silver, lead, jasper, amethysts, topazes, emeralds, yellow amber, rock-salt, and coal. The population of the government exceeds 325,000, and consists of Buriats, Tunguses, and Russians. The inhabitants are for the most part employed in agriculture, and to some extent in fishing and hunting. As a local industry, the manufacturing of an excellent oil out of stone-pine nuts deserves notice. The foreign commerce consists in the trade with China, carried on through TroitzkoSavsk and Kiachta (q. v.), and has risen to great importance in recent times.

The government of I. is divided into two districts-Irkutsk and Kirensk-and the township of Kiachta. The capital is Irkutsk; the other towns are Telma, with a cloth-factory, Troitzko-Savsk, Kiachta, Kirensk on the Lena, Nijneudinsk, and Verkholensk.

7.844) occurs more abundantly than any other IRON (sym. Fe [Lat. ferrum], eq. 28, sp. gr. metal. In its native form it is chiefly found in meteoric stones (see AEROLITES), and in certain ores of platinum, and is consequently of compara IRKUTSK, capital of the Russian government tively rare occurrence, but the so-called iron ores of that name, is the residence of the governor--the oxides, sulphides, &c.—are very widely disgeneral of Eastern Siberia, and the seat of a tributed. The most important of these ores are bishop. It is situated on the right bank of the mentioned below. Angara, near its confluence with the river Irkut, in lat. 52° 17′ N., and long. 104 26′ E., and is 3842 miles distant from St Petersburg. The town is about 1200 feet above the level of the sea, and

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 heating the protochloride in a glass tube through which a current of dry hydrogen is passed. In this case, pure iron is deposited as a glistening mirror on the glass.

This important metal will be most conveniently considered under the three heads of

applications in technology are noticed in the article VITRIOLS, BLUE AND GREEN.

Phosphate of iron is obtained by precipitating a solution of a protosalt of iron with phosphate of soda, when a white precipitate of phosphate of iron is thrown down.

All these salts, especially the carbonate and sulphate, are extensively used in medicine. Silicate and phosphate of iron occur naturally in several minerals.

The peroxide of iron, termed also sesquioxide, red oxide, or ferric oxide, is obtained in an anhydrous form by igniting the protosulphate, and is known in the arts under the names Colcothar, Crocus of Mars, or Rouge, according to the degree of levigation to which it has been submitted. It is employed for polishing glass, jewellery, &c., and is also used as a pigment. It occurs both in the anhydrous and in the hydrated form in various minerals.

1. Chemistry of Iron.—Chemically 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 bar or wrought iron. Its colour 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 melting 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 The hydrated peroxide (2Fe,O,,3HO) is obtained it possesses very little malleability, as compared with by precipitating a solution of a persalt of iron or gold and silver. In ductility, it stands very high, of a ferric salt, with an excess of potash, ammonia, being barely exceeded by gold, silver, and platinum; or alkaline carbonate. It falls as a yellowishand in tenacity, it is only exceeded by cobalt and brown flocculent precipitate, which when dried nickel. Its susceptibility to magnetism is one of its forms a dense brown mass. This hydrated peroxide most remarkable characteristics. See MAGNETISM. of iron, when freshly prepared and suspended in At a high temperature, it burns readily, as may be water, is regarded as an antidote in arsenical poisonseen at the forge, or (more strikingly) when a glow-ing, Rust, as has been already mentioned, is a ing wire is introduced into a jar of oxygen. In hydrated peroxide, combined with a little ammonia. dry air and at ordinary temperatures, the lustrous The most important of the persalts of iron, or ferric surface of the metal remains unchanged; but in a salts, are the neutral and the basic sulphate, whose moist atmosphere the surface rapidly becomes oxi- formulæ are Fe2O3,3SO, and Fe2O3,350.5Fe0, dised and covered with rust, which consists mainly respectively, the nitrate (Fe,O,,3NO), the phos of the hydrated oxide of iron. At a red heat, phate, and the silicate. Of these, the neutral iron decomposes water, and liberates hydrogen, the sulphate, the phosphate, and the silicate occur in oxygen combining with the iron to form the black various minerals. The nitrate, which is obtained or magnetic oxide (Fe ̧04), which occurs in minute by the solution of iron in nitric acid, is a useful crystals. This is one of the ordinary methods of medicinal agent. obtaining hydrogen.

3

The affinities of iron for most of the non-metallic elements are very powerful. The chief of the iron compounds are

a. Oxides of Iron.-Iron forms four definite compounds with oxygen-viz. (1), the protoxide (FeO), which is the base of the green or ferrous salts of iron; (2), the sesquioxide or peroxide (Fe,O), which is the base of the red or ferric salts; (3), the black or magnetic oxide (Fe3O4), which is regarded by some chemists as a compound of the two preceding oxides; and (4), ferric acid (FeO3). The protoxide cannot be obtained in an isolated form, but it forms the base of various ferrous 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 sulphate, the phosphate, and the silicate.

Carbonate of iron (FeO,CO2) exists 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 (FeO,SO3 + 7HO) is obtained by the solution of iron, or its sulphide, in dilute sulphuric acid; in the former case, there is an evolution of hydrogen, and in the latter, of sulphuretted hydrogen. The reactions in the two cases are expressed by the equations,

Fe +SO,,HO= FeO,SO, + H FeS+SO,,HO= FeO,SO3 + HS. On evaporation of the solution, the salt is obtained in clear bluish-green rhomboidal crystals, containing seven atoms of water. This salt is commercially known as copperas or green vitriol, and its various

The black or magnetic oxide and ferric acid, which has not been obtained in a free state, and is only known as a constituent of certain salts, must be passed over without comment.

b. Haloid salts of iron-the chlorides, bromides, and iodides-next require notice. There are two chlorides-viz., a protochloride (FeCl) and a perchloride or sesquichloride (Fe,Cl). The latter may be obtained by dissolving peroxide of iron in hydrochloric acid. The tincture of the sesquichloride of iron is perhaps more generally employed in medicine than any other preparation of this metal. The protiodide is an extremely valuable therapeutic agent. c. There are probably several sulphides or sulphurets of iron. The ordinary sulphide is a protosulphide (FeS). It occurs in small quantity in meteoric iron. It may be obtained artificially by the direct union of the two elements at a high temper ature, or by the precipitation of a protosalt of iron by sulphide of ammonium. It exists in glistening masses, varying in colour from a grayish yellow to a reddish brown. It is insoluble in water, but in moist air becomes rapidly oxidised into protosulphate of iron. With acids, it develops sulphuretted hydrogen. The bisulphide of iron (FeS2) is the iron pyrites of mineralogists, and the mundic of commerce. Under the latter name, it is used extensively in the preparation of oil of vitriol. There are also other sulphides of less importance.

The protosalts and the persalts, or the ferrous and the ferric salts, give totally different reactions with the ordinary tests. The solutions of the former have a greenish colour and a peculiar metallic taste, while those of the latter are generally of a brownishyellow colour, and are very acid. Sulphuretted hydrogen gives no precipitate with an acid solution of a ferrous salt, while it gives a milky precipitate

of sulphur with a solution of a ferric salt. Potash, or brown iron ore; 3. Magnetic, or black iron ore; soda, and ammonia throw down a white hydrated 4. Ironstone, blackband, or clay iron ore; 5. Bog oxide from the former, and a brown hydrated iron ore, or phosphate of iron. peroxide from the latter. Ferrocyanide of potassium gives with ferrous salts a white precipitate, which soon becomes blue, while with ferric salts it at once produces a blue precipitate, even in a very dilute solution. Tincture of galls (tannic acid) produces no immediate change of colour with the ferrous, but a deep blackish-blue colour (ink) with the ferric salts. Sulphocyanide of potassium produces no change with the ferrous, but gives a deep blood-red tint with the ferric salts. Succinate and benzoate of ammonia produce no precipitate or change of colour with the former, while with the latter, if the solution is not too acid, they throw down pale reddish-brown precipitates.

the cabinet of the mineralogist. But there remains the Memoirs of the Geological Survey, and the second to be noticed a dull, blackish or clay-coloured is by Dr Murray Thomson. nineral, possessing no beauty or symmetry, which Great Britain prizes as one of the greatest of her

mineral treasures: this is the ironstone of the coalmeasures, which is variously named clay iron ore, clay carbonate of iron, and blackband. It is essentially a mixture of carbonate of iron with clay, containing also water, and in the case of blackband, coaly or bituminous matter. It is estimated that the coal-measures of Great Britain produce about nine-tenths of our iron; and it is a fortunate thing that, along with the ore, are found both the fuel and the limestone that are indispensable for its reduction.

About ten years ago, the three great iron districts of Britain were South Staffordshire, South Wales, and Central Scotland, each producing nearly equal quantities, and together yielding about four-fifths of the total produce of the country. Now, however, the South Staffordshire field is being rapidly exhausted, its produce having diminished about a half, while that of the South Wales and Scottish districts have increased, and they are now yielding nearly a million tons each. North Staffordshire, Shropshire, Derbyshire, and the West Riding of Yorkshire are the principal remaining districts yielding ores of this class, but their total produce is not more than that of South Staffordshire, although the iron of the West Riding is the best in Britain as regards quality.

CLAY IRONSTONE, CHIEFLY A CARBONATE OF IRON, BLACK-BED

MINK, LOWMOOR, YORKSHIRE,

28.36

Sulphur,

Metallic iron per cent.

There is yet another great iron district, yielding an ore belonging to a more recent formation than It will be noticed that in the case of these ores the the carboniferous beds-namely, the lias. This impurities are rather numerous. Nevertheless, the deposit, which fifteen years ago was unknown, is modes of preparing and smelting them are somealready producing iron to the enormous amount what rude and simple, as the low price of iron will of 400,000 tons per annum. It is the ironstone not permit of its ores being treated with the same of the Cleveland Hills, in the north-east of York- care as the ores of lead, copper, tin, and some other shire, which, from its resemblance to common sand- metals. stone, passed unnoticed till 1847. About that time, isolated blocks of it, found on the sea-coast, were discovered to contain about 30 per cent. of iron. On further examination of the district, these were proved to be detached pieces of a massive bel, no less than 15 feet thick, which could be traced for many miles along the sides of the hills. Some idea of the value of this vast deposit of iron ore will be found in the fact, that the ironstone seams of the coal-measures seldom exceed 20, and are worked as low as 8 inches in thickness. Another mass of ironstone of great thickness, also belonging to the lias beds, has very recently been discovered in North Lincolnshire. In the oolite, too, beds of brown iron ore have been discovered in several counties, but chiefly in Northamptonshire, where it has been worked with so much spirit, that from 150,000 to 200,000 tons of ore per annum are now raised.

To those remarkable discoveries may be added that by Mr Rogers of Abercarn, who, after examining the position of the pisolitic ore at the base of the carboniferous limestone in Belgium, searched the corresponding strata in South Wales, and curiously enough was rewarded with the discovery of a precisely similar bed at Cwm Noddi. The same gentleman, struck by the appearance of the sparry carbonates of iron in the Austrian and Prussian departments of the Exhibition of 1851, soon afterwards noticed veins of a like ore in the Devonian rocks of Somersetshire. In fact, the sources which have been discovered within the last fifteen years are already yielding a larger supply of iron than the total produce of any other European country except France.

Before proceeding to describe the manufacture of iron, we give two analyses of British ores: the first is by Mr J. Spiller, taken from a series published in

Iron ore is still reduced in the south of Europe by the old and imperfect process of the Catalan forge, not unlike a common smith's forge. In Great Britain, however, as well as in all other countries where iron is largely smelted, the blast-furnace is now universally employed, by means of which the metal is obtained in the state of crude or cast iron. For the finer kinds of iron, charcoal is the fuel employed, because, unlike coal or coke, it contains no sulphuret of iron or other injurious ingredients. The Russian and Swedish furnaces smelt with charcoal, and on this, as much as on their pure ores, depends the high reputation of their iron. A solitary charcoal-furnace at Ulverstone in England, and another at Lorn in Scotland, are still working-the only relies of times past, when this was the only fuel employed.

As a preliminary process to the actual smelting in the blast-furnace, clay and blackband ironstones are generally roasted. This is accomplished by breaking the ore into small pieces, spreading it in open heaps on the ground, and mingling it more or less with small coal according to the nature of the ore. Blackband commonly contains enough of carbonaceous matter to burn without the addition of coal. The pile, which may contain from one to several thousand tons of ore, is lighted at the windward end, and burns gradually along, aided by occasional fires in the sides, till the whole heap has undergone calcination, the time required for this purpose being generally about a month. Sometimes the operation of roasting is performed in close kilns, instead of open heaps, a mode by which the ore is considered to be more uniformly roasted, and with considerably less fuel. By calcination, clay ironstone loses from 25 to 30, and black band from 40 to 50 per cent. of its weight, the loss consisting