Iron, the hardest and most extensively useful of the imperfect metals : it is naturally of a livid, whitish-grey colour, and found in great abundance in various parts of the world, both in a pure state, and intermixed with other fossil matters.
The iron manufactured in Great Britain is obtained from three different kinds of ores : 1. The Lancashire ore, thus denominated from the county where it abounds ; being very heavy; of a fibrous texture ; a dark purple colour, inclining to black; and lodged in veins like other metals. 2. The log ore, which resembles a deep yellow clay, and has probably been deposited by some ferruginous rivulets: it is found in strata from 12 to 20 inches thick, and of various breadth. 3. Iron stones, of an irregular shape, which frequently lie in beds of great extent, and, like other stony masses, are sometimes intersected with seams or veins of pit-coal.
After the ore is dug out of the earth, it is crushed in a mill, and washed in a stream, in order to separate the grosser particles of earth. Next, it is melted in furnaces, maces, heated with coke, charcoal, peat, or turf; near the bottom of which, by means of a tap-hole, the liquid metal is discharged into furrows made in a bed of sand. The larger mass, which settles in the main furrow, is called by the workmen, a sow ; and the smaller ones, pigs of iron. Stoves, grates, etc. are formed by casting ladles full of the rough metal into proper moulds made of sifted sand. In this state it is called cast-iron but, if cooled too hastily, it be-, comes brittle, and is apt to crack like unannealed glass : it is not malleable, and is so hard as to resist the file. With a view to improve it, the raw iron is now melted down a second time in another furnace, where a strong blast of air is impelled on the surface of the metal ; in consequence of which its fusion is considerably facilitated, and the iron concretes into a mass called a loop, that is conveyed beneath a large hammer raised by the motion of a water-wheel. The metal is there beaten into a thick square form, again heated so as nearly to melt it, and then forged. By repeating this process, the iron is rendered perfectly malleable, and at length formed into bars for sale. Lately, however, cast-iron has been reduced to a state of malleability, by passing it through rollers, instead of forging it. For this valuable improvement we are indebted to Mr. Henry Cort, of Gosport, who in the year 1783, obtained a patent for preparing, welding, and working various sorts of iron, by means of machinery, etc.- As, however, this specification would be intelligible only to iron manufacturers, the inquisitive reader will consult the 3d vol. of the Repertory of Arts, etc. Yet justice'requires us to observe, that the raw, or cast-iron is, by Mr. Cort's process, perfectly freed from those impurities which are not discharged by the common methods of rendering this metal malleable ; and that it has been proved by experience to be equal, and, in. some cases, superior, to the best Swedish iron. As Mr. C.'s patent is now expired, we trust it will be generally adopted at Birmingham, Carron, Colebrook-Dale, and the other iron manufactories of Britain; because the metal thus treated, may not only be procured at a cheaper rate than it is sold at present, but a saving will be made of one mi/lion sterling per annum, which is now paid to Sweden and Russia for bars, while we possess-a sufficient quantity of the raw materials, which may be worked at home to that amount.
Beside the cast and forged iron, there is an intermediate state, in which that metal is soft and tough. This is called steel., and is usually made from the best forged iron, by cementation with certain inflammable matters: some account of the process will be inserted in its alphabetical series.
Iron being of such essential ser-vice for a great variety of purposes, several persons have obtained exclusive privileges for different inventions to which it may be applied.- Among these, the patent granted to Mr. Jonathan Taylor (now expired) for casting oval-bellied pots, and nealing, turning, and finishing the same, etc.; then Mr. Rowlandburdon's, in 1795, for a method of making, uniting, and applying cast-iron blocks, to be substituted for key-stones, in the construction of arches; and for making cast metal or pig iron from the ore, and manufacturing it into bar, or any other malleable iron, deserve particular notice.-The reader will find these, together with the various patents relative to the iron manufactory, minutely described in the different volumes of the Repertory of Arts and Manufactures.
Beside its utility as a material for implements of agriculture, etc. iron is eminently adapted to the purpose of dyeing cotton. From the various experiments made by Chap-tal, it appears that the oxyd of iron has so great an affinity for cotton thread, that if the latter be immersed in a saturated solution of this metal in any acid, it assumes instantaneously a chamoy-yellow colour, which becomes more or less deep, according to the strength of the liquors, and the length of time it has been exposed to the air. The colour thus communicated is fixed; resists both air and water, and also alkaline leys ; nor is its durabiliTy in the least affected by washing it with soap; which, on the contrary,' imparts to it additional brightness. The oxyd of iron, if precipitated on any stuff, easily unites with the fawn colour obtained from vegetable astringents ; and, by varying the strength of the soda, soap, or other mordants employed in dyeing, an infinity of shades may be produced. Thus, by means of a boiling heat, the oxyd of iron may be more intimately combined with the astringent principle. These colours may likewise be rendered brown, as they are susceptible of a variety of shades, from a bright grey to a deep black tint; by simply passing the cotton impregnated with astringent vegetable matter, through a solution of iron.
"When long exposed to the air iron is very liable to become rusty, especially in moist situations: hence an effectual method of preserving it bright, still remains to be discovered. Various compositions have indeed been contrived for this pur-pose; but none appears to be more serviceable than common oil, though its use is on many occasions both troublesome and disagreeable. To obviate these inconveniencies,it has been recommended to heat the iron to such a degree, that it cannot be touched without burning the hand, then to varnish it with new white wax, and expose it to the lire, till the wax is completely imbibed by the metal, which should next be rubbed over with a piece of serge. -According to others, this metal may be perfectly secured from the effects of rust, by plunging it, while red-hot, into linseed-oil, which is suffered to drop off till it become dry, and then wiping the iron with a clean cloth. Thus a black crust or varnish is formed, which renders it impervious to moisture. Again, others pour melted lead into the oil, before it is applied to the heated iron ; but both preparations require a considerable degree of skill and precaution.
Iron, when imported in British ships from the United States of America, is exempt from duty ; but if it be brought in American vessels, it is liable to a duty of 5s. 7 1/2d. per ton, and 10s. lOd. per ton for convoy-duty.-The sum of 10s. 10 1/2d. is paid on iron, whetheir in rods, or drawn, or hammered less than three-fourths of an inch square, if imported from Russia in British ships ; but, if in foreign bottoms, it is subject to the duty of 11s. 3 1/2d. per cwt.
In medicine, iron is chiefly em ployed as a tonic and corroborant: When properly prepared, it is given with advantage in diseases proceeding from laxity and inactivity of the digestive organs, such as indigestion, flatulency, colic, etc. It is also of considerable service in hypochondriacal affections, intermittent, tertian, quartan, and other fevers ; but it seldom agrees with either bilious or plethoric constitutions, and is, like all active drugs, much abused by quacks and other pretenders, who should not be suffered to trifle with the health and lives of the multitude.
Iron-moulds, are spots on linen, occasioned by its exposure to damp situations, and also by ink accidentally dropped on the cloth. They may be removed by moistening the stained part, sprinkling it with a small quantity of the essential salt of lemons; after which the linen is to be rubbed over a pewter plate, and the blot washed out with warm water. But a less expensive method consists in wetting the spot, applying to it a few drops of spirit of salt, or lemon juice; then rubbing it for a minute or longer between the fingers, while it is carefully held over a hot smoothing iron, or a bason filled with boiling water, the steam of which greatly facilitates the removal of the stains.
Iron. - As vessels, made of this metal, are liable to cracks, which frequently render them useless, we insert, on the authority of M. Kas-teleyn, the following directions for preparing a lute calculated to fill up such fissures : - Take six parts of yellow potter's clay, and one part of iron filings; incorporate these ingredients with a sufficient quantity of linseed oil, so as to form the whole into a paste of the consistence of putty.
Although a variety of varnishes have been contrived for securing iron and steel, in a polished state, from the effects of rust; yet we are persuaded, that the following is the roost simple and effectual method of preserving them. It is well known, that the oil expressed from the fruit of the chocolate-tree never becomes rancid, provided the nuts have been moderately roasted, before they are submitted to the press. This oil is asserted by M. Von Crell, to be eminently adapted to the purpose before stated: and we may add, from recent experience, that the animal oil obtained from eels, if applied to polished iron, steel, or other metals, especially when used in machinery, such as wheel-work, has been attended with similar good effects.