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In Germany it is used for the manufacture of arsenious acid, and is sometimes mixed with iron ores; but it is very apt to choke the top of the blast furnace, for the arsenic, evaporating in the greater heat of the hearth, condenses at the cooler top.

The most interesting deposits of this ore are in the United States; at Franconia, N. H., Worcester, Mass., and Chatham, Conn.

A small quantity of this material, mixed with the other iron ores, does no harm to the product; a larger quantity occasions it to be cold-short, and is troublesome in the blast furnace.

VII. Chlorides of Iron.

Chloride of iron should hardly be ranged among the ores of iron, but in many respects it deserves our attention. Chlorides are frequently found among the iron ores of the hydrates as a chloride of iron, or of sodium, and in some other unimportant combinations; their presence is unquestionable. We find indications of chlorine on the top of burnt ore piles, and in the wash-water of iron ores. Chlorides are seldom or never found in the more ancient deposits, and occur only in the hydrates, or brown iron ore. Their presence in smaller quantities is very favorable, and promotes the operations in the blast furnace; it accelerates the motion of the charges, and furnishes a liquid, lively cinder. Such ores are very apt to furnish gray iron, of an excellent quality for the forge, though generally too cold-short for the foundry. Larger quantities of chlorides occasion trouble in the blast furnace, and produce white pig metal; but the metal is alway of good quality.

VIII. Sulphates of Iron.

Sulphuric acid has great affinity for the oxides of iron, and can with difficulty be entirely separated from such. Neither heat nor strong alkalies separate the oxide of iron from the sulphuric acid, and under all circumstances a part of the acid is left in an oxide or iron ore, where it is combined. Iron masters are not very apt to make use of the sulphates of iron, either as green, white, or red copperas; but in that large body of iron ores, the hydrates, particularly those of the coal formation, there is more or less sulphuric acid mixed with the ore; and, as this acid cannot be expelled entirely by heat, it is a dangerous enemy to the manufacturer. Whether sulphuric acid is, or is not, in the ore, can be ascertained by pounding, and heating it to redness along with some filings of wrought iron,

and by dissolving the protosulphate which is formed in water; that is, wash the whole mass in rain water, and test with chloride of barium for sulphuric acid. Sulphuric acid is generally found in the yellow hydrates, but may be observed in the whole class of hydrates.

The great disadvantage arising from sulphuric acid in iron ores, is its indestructibility by heat; and if, besides heat, carbon is present, then the sulphuric acid is decomposed, and leaves sulphuret of iron. This happens either in the calcining process, or in the blast furnace, and on that account sulphuric acid acts in the same manner as sulphur itself, or pyrites, and occasions hot-short iron.

IX. Phosphate of Iron.

Phosphate of iron, green iron ore, is of a dull blue color, and turns yellowish-brown before the blowpipe; or, in the reducing flame, into a black, porous slag; it is not magnetic, and it is soluble in hydrochloric acid. It is often dark lake green, and of a vitreous, silky lustre.

Its composition is, in 100 parts,

62.52 oxide of iron

28.50 phosphoric acid

8.98 water

100.00 phosphate of iron.

This ore is seldom found in large masses, but frequently interspersed in other ores, and for that reason we take notice of it. It occurs in small particles of aggregated plates, sometimes only visible by means of a microscope. Generally, this phosphate is mixed with the yellow hydrates, fossiliferous and bog ores, and is the cause of very cold-short iron; and on this account is, if not to be rejected, at least to be regarded with great suspicion. Still, the ores of this kind have one great advantage-that is, of furnishing a cheaper iron than that from all the other ores; the phosphorus can be completely removed in the puddling furnace. Where such ore occurs, it is generally in large bodies, and can be easily wrought; so that the price of the ore is not to be considered an objection to it. It is, of all classes of ore, the best in the blast furnace, and consumes less fuel than any other kind. Where forges are in such a condition as to work the cold-short metal into salable bar iron, or into any particular form, it is, beyond question, the

most available. In the course of this work we shall have opportunities to refer to this subject again.

In Europe, particularly in the plains of Russia and Prussia, there are immense masses of bog ore, from which large quantities of iron are manufactured. These ores contain more or less of the phosphate, and the iron produced is cold-short. In the United States, we believe, there is but little of this ore; Michigan and Ohio contain it in small quantity. There may be bog ore in Alabama, Arkansas, and Florida but the fossiliferous ore of Pennsylvania and Maryland contains phosphate of iron.

X. Carbonate of Iron.

Sparry Iron; Brown Spar.-This most important species contains two varieties; the spathose, or sparry iron ore, and the compact

carbonate.

a. Sparry, or Spathic Iron, Steel Iron Ore, is of a lamellar sparry fracture. Color, yellowish-gray, Isabella, or even brownish-red; turns brown before the blowpipe, and is then attracted by the magnet. After being taken from the mine, it assumes a brown tint by exposure to the atmosphere; gives a slight effervescence with nitric acid, and changes to a brown color. Manganese and magnesia, as well as carbonate of lime, are frequently found mixed with it. It melts into a green glass with borax.

Its composition varies, but a specimen from Europe contained 63.75 protoxide of iron 34.00 carbonic acid

0.75 oxide of manganese

0.72 magnesia

0.78 lime and water

100.00 sparry iron ore.

Sparry carbonate belongs to the primitive formation, forming vast veins and layers in gneiss and primitive slate and limestone; it is associated with quartz, copper pyrites, gray copper, fibrous brown oxide of iron, and carbonate of lime. Beds of immense quantities are found in Styria, forming at Eisenerz a mountain as high as the snow line, from which ore was dug by the ancient Romans. These beds appear inexhaustible. In Carinthia an excellent ore of this kind exists, from which iron and steel of the first quality are produced. In fact, most of the iron and steel of Austria is derived

from this ore. It is distributed all over Germany; and the cheap, though celebrated, German steel is manufactured from sparry iron ore. The cutlery and weapons of Solingen, in Western Germany, are made from iron and steel of the sparry ore, which is dug in Siegen, occurring in heavy veins and beds in transition slate. This ore is found in France, England, Scotland, Russia, Spain, Switzerland, and various other countries.

A very considerable vein of spathic iron is found near Roxbury, Conn., traversing a vein of quartz, imbedded in gneiss; also in Plymouth, Vt.; and in small quantity in Monroe, Conn.

This is a very valuable and interesting species. It affords steel with the greatest facility, and is one of the most favorable ores in the Catalonian forge. By proper treatment, it produces an excellent kind of bar iron, which is sufficiently esteemed by the black- smith.

b. The Compact Carbonate of Iron-spherosiderite argillaceous iron ore has no relation externally with the sparry variety; it comprehends most of the clay iron stones of the coal measures, particularly those which occur in flattened spheroidal masses, varying in size from the dimensions of a small bean to pieces weighing a ton. The color of this ore is commonly a dirty blue or gray, brown, reddish-brown, and yellowish-brown. Fracture close-grained, hard, streaked white or brown. Blackens before the blowpipe, and, if calcined, is attracted by the magnet.

This carbonate of iron, though belonging to the coal formation, is found in various places in the tertiary strata. It is the principal ore from which iron is smelted in England and Scotland, and yields usually from 30 to 33 per cent. of metal. It is largely distributed over the United States. Pennsylvania abounds in it. It exists in Maryland, Virginia, Ohio, Illinois, North Carolina, and Kentucky. The difficulty of working this kind of ore in the blast furnace, of which we shall speak in another chapter, may be assigned as the reason why it is not more generally in use. England and Scotland use it extensively, and work scarcely any other kind.

Prof. Rogers, in his Reports of the Geology of Pennsylvania, has given a great many analyses of argillaceous ores, of which we shall select the following:

In 100 parts of or were found:

53.03 protoxide of iron

35.17 carbonic acid

3.33 lime

1.77 magnesia

1.40 silica

0.63 alumina

0.23 peroxide of iron

3.03 bitumen

1.41 water

100.00 argillaceous ore.

This may be considered, an analysis of one of the best specimens. Generally these ores contain no more than 30 per cent. of iron; and an average of the argillaceous ores of the Pennsylvania and Maryland coal measures would not go further than 25 per cent. The compact carbonates afford with charcoal and cold blast an excellent forge iron; by the hot blast the quality is greatly injured; but if properly calcined, and the burden not too heavy, it forms an excellent gray foundry metal. Still, the operations in the yard, of roasting and those of the blast furnace, are somewhat difficult, particularly for those who are not very experienced founders, and acquainted by practice with this kind of ore. In the chapter on blast furnaces we will refer to this subject.

XI. Titanate of Iron.

Titaniferous Iron, Iron Sand, is an oxide of iron and titanic acid, and belongs to the class of the magnetic oxides. It is attracted by the magnet, is of a deep black color, metallic lustre, very hard, and perfectly opaque; melts into a black slag by a high temperature. It is generally found near volcanoes or volcanic rocks, but seldom in quantities sufficient to justify the erection of iron works; nevertheless, the quality is mostly good, and the volcanic regions around the lakes may present, in the course of time, encouraging prospects.

There are two classes of iron ore which do not belong properly to our department, but are interesting as well on account of their belonging to the United States alone, as on account of their large quantity and usefulness. For this reason we shall notice them.

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