Iron unites with gold, silver, and pla tina. When heated to a white heat, and plunged in mercury, it becomes covered with a coating of that metal. Long tri turation of mercurial amalgams likewise causes a coating to adhere to the ends of iron pestles ; small steel springs, kept plunged beneath the surface of mercury in certain barometers, become brittle in process of time ; and the direct combina tion of iron and mercury in the form of an amalgam may be obtained, according to Vogel, by triturating the filings with twice their weight of alum, then adding an equal weight or more of mercury, and continuing the friction, with a very small quantity of water, till the union is com pleted. Mr. A. Aikin unites an amalgam of zinc and mercury with iron filings, and then adds muriate of iron, when a decom position takes place, the muriatic acid combining with the zinc, and the amal gam of iron and mercury assuming the metallic lustre by kneading, assisted with heat. Iron and tin very readily unite together,, as is seen in the art of tinning iron vessels, and in the fabrication of those useful plates of iron, coated with tin, which are generally distinguished by the simple name of tin alone. The chief art of applying these coatings of tin con sists in defending the metals from oxida tion by the excess of air. After the iron plates are scraped,or rendered very clean by scouring with an acid, they are wetted with a solution of sal ammoniac, and plunged into a vessel contaii.ing melted tin, the surface of which is covered with pitch or tallow, to preserve it from oxy dation. The tin adheres to, and intimate ly combines with, the iron to a certain depth, which renders the tinned plates less disposed to harden by hammering than before ; as well as much less dis posed to alter by the united action of air and moisture. The process for tinning iron vessels does not essentially differ from that which has already been de scribed for copper vessels. Iron does not unite easily with bismuth, at least in the direct way. This alloy is brittle, and at tractable by the magnet, even with three fourths of bismuth. As nickel cannot be purified from iron without the greatest difficulty, it may be presumed that these substances would readily unite, if the ex treme infusibility of both did not present an obstacle to the chemical operator. Arsenic forms a brittle substance in its combination with iron. Cobalt forms a hard mixture with iron, which is not easi ly broken. The inflammability and vola tility of zinc present an obstacle to its combination with iron. It is not improba. ble, however, but that clean iron filings would unite with zinc, if that metal were kept in contact with them for a certain time, in a heat not sufficient to cause it to rise ; for it has been found, that zinc may be used in the operation of coating iron in the same manner as tin. Anti mony unites with iron, and forms a hard brittle combination, which yields in a slight degree to the hammer. The sul phuret of antimony is decomposed by vir tue of the greater affinity of the iron to the sulphur. For this purpose, five ounces of the points of nails from the farriers may be made red hot in a crucible, one pound of pulverized ore of antimony must then be thrown into the crucible, and the heat quickly raised to fuse the whole. When the fusion is perfect, an ounce of nitre in powder may be thrown in, to facilitate the separation of the scoriae. After the mass is cooled, the antimony is found separate at the bottom of the cru cible, while the iron remains in combina tion with the sulphur and alkali. If the proportion of the iron be considerably greater than five ounces to the pound of ore, the antimony will be alloyed with iron. Manganese is almost always united with iron in the native state. Tungsten forms a brittle,whitish-brown, hard alloy, of a compact texture, when- fused with white crude iron. The habitudes of iron with molybdena are not known.
Iron is the most diffused, and the most abundant, of metallic substances. Few mineral bodies or stones are without an admixture of this metal. Sands, clays,
and the waters of rivers, springs, rain, or are scarcely ever perfectly free from it. The,parts of animal and vege table substances like wise afford iron in the residues they leave after incineration. It has been found native, in large masses, in ) - Siberia, and in the internal parts of South t' America- This metal, however, in its tive state is scarce : most iron is found in the state of oxide, in ochres, bog ores, and ir. other friable earthy substances, of a red, brown, yellow, or black colour. The - hematites, or blood stones, are likewise ores with oxide of iron : these are either .> of a red colour, or blue, yellow, or brown. - An iron ore is likewise found, of a blue t:, colour, and powdery appearance. This t useful metal is so abundant, that whole mountains are composed of iron stone ; whereas other metals usually run in small ., veins. Besides these ores of iron, which I are either nearly pure, or else mixed with earths, as in spars, jaspers, boles, basaltes, &c. iron is mineralized with sulphur, as in the pyrites, or with arsenic. The coally iron ores contain bitumen. The magnet, or load stone, is an iron ore, the constitu tion of which has not yet been accurate ly examined. Iron is also found in corn .
imitation with the sulphuric acid, either -,: dissolved in water, or in the form of Ka phate.
-. To analyse the ores of iron in the humid way, they must be reduced to a very sub i tle powder, and repeatedly boiled in mu ', riatic acid If the sulphureous ores should prove slow of solution, a small quantity 1 of nitric acid must be added to accelerate the operation. The iron being thus ex tracted, the insoluble part of the matrix only will remain. Prussiate of potash be ing added to the decanted solution, will precipitate the iron in the form of Prus .. sian blue. This precipitate, when washed and dried, will be equal in weight to six ' times the quantity of metallic iron it con tains ; and from this iron four parts in the ''' hundred must be deducted, to allow for P.'. the iron Which is contained in the prus slate of potash itself. But as this alkali, and every other preparation containing the prussic acid, does not constantly afford the same quantity of iron, the most exact way, in the use of such preparations, con , sists in previously dissolving a known quantity of iron in sulphuric acid, and precipitating the whole by the addition of the prussiate of potash. This result will afford a rule for the use of the same alkali in other solutions. For as the weight of the precipitate obtained in the -- trial experiment is to the quantity of iron which was dissolved and precipitated, so is the weight of the precipitate obtained from any other solution to the quantity of iron sought.
If the iron be united to any consider , able proportion of zinc or manganese, the Prussian blue must be calcined to red ness, and treated with strong nitric acid, which will take up the oxide of zinc. The manganese may then be dissolved by nitric acid with the addition of sugar ; and the remaining iron being dissolved by munatic acid, and precipitated by sub carbonate of soda, will afford 22.5 grains of precipitate for every 100 grains of metallic iron.
To examine the ores of iron in the dry way, the only requisite is fusion, in con tact with charcoal. For this purpose eight parts of pulverized glass, one of calcined borax, and half a part of char coal, are to be well mixed together. Two or three parts of this flux being mixed with one of the pounded ore, and placed in a crucible, lined with a mixture of a little clay, and pounded charcoal, with a cover lilted on, is to be urged with the strong heat of a smith's forge for half an hour. The weight of the ore, in this ex periment, should not exceed sixty grains. Other processes for determining the con tents, or metallic product, of iron ores, are instituted, by performing the same operations in the small, as are intended to be used in the large way.