The art of obtaining metals from their ores, comprising the processes of a.s.saying, refining, smelting, &c. By a.s.saying is meant, the particular manner of examining an ore or mixed metal, according to its nature, so as to discover not only what metals and what proportions of metal may be obtained from it, but also what other mineral substances or earths may be contained in it.

What do the terms Refining and Smelting signify?

Refining is the art of rendering the metal free from all impurities.

Smelting means the melting of a metal from its ore in a smelting furnace, in order to separate the metallic parts from the sulphur, a.r.s.enic, and the earthy and stony substances with which they may be combined.

What is Sulphur?

An inflammable, fossil substance, of a dry, solid, friable nature, melting with a small proportion of heat;--when fired in the open air, burning almost entirely away with a blue flame and noxious vapor. It is abundantly diffused in many places, especially where metallic minerals are found; but more particularly in those districts where subterranean fires and volcanoes exist. It is also found combined with many different substances.

Describe the nature of Sulphur, and the places where it is mostly found.

Sulphur almost pure, called native or virgin sulphur, is found in volcanoes and grottoes, in the form of transparent crystals; but the greatest quant.i.ty which exists naturally is combined with metals in ores. Sulphur is both fusible and volatile,--which qualities enable us to procure it from those minerals by the process of sublimation: it unites easily, in different degrees, with all metallic matters, excepting gold, platina, and zinc.

_Sublimation_, the act of bringing a solid substance into the state of vapor by heat, and condensing it again by cold.

Are not its uses very extensive?

Yes, both in the arts and in chemistry: it is well known to be a princ.i.p.al ingredient in the preparation of gunpowder and fire-works; it is also used for whitening wool, straw, silk, &c.; many other matters exposed to the vapors of sulphur when burning, quickly lose their color, which no other substance had been able to destroy.

Sulphur is also frequently found in mineral waters.

Whence are the greatest quant.i.ties of Sulphur brought?

The largest quant.i.ties are brought from Saxony, in irregular ma.s.ses, which are afterwards melted and cast into small rolls. There are about four species of sulphur; namely, the yellow native sulphur, which in its purest state is clear, and of a pale straw color, found in the gold mines of Peru; in Hungary, and some other places: the green native sulphur, which is harder than the other, is found in small crust-like ma.s.ses; this sort is chiefly confined to Mount Vesuvius: and the grey native sulphur, common in Iceland and many other places.

Native sulphur is also found at the coal mines, near Richmond, Virginia; in Connecticut, Pennsylvania, and other parts of the United States.

Which is the most rare and beautiful of all the kinds?

The red native sulphur; it is mostly of a fine glowing red, very bright and transparent; it is found, like the first-mentioned sort, in the gold mines of Peru. Common sulphur, such as is used in trade and the arts, is of a pale yellow color; and possesses a peculiar and disagreeable smell, particularly when heated or rubbed. This is mostly extracted from the metallic sulphurets, and is commonly called brimstone. It is the sort employed in making matches.

Is there not another substance also employed in the manufacture of matches?

Yes: Phosphorus, a peculiar substance, chiefly of animal origin. It is mostly procured by the decomposition of the phosphoric acid which is found in bones. It was accidentally discovered at Hamburgh, in 1669, by an alchemist named Brandt.

_Alchemist_, one skilled in Alchemy.[15]

[Footnote 15: See Chapter XVIII., article Chemistry.]

What is the nature of Phosphorus?

It is a solid, inflammable substance, which burns when in contact with atmospheric air. It is used in various chemical experiments, and for making matches; for various kinds of fire-works, &c. It will combine with all metals except gold and zinc; and also with some earths. Some animals, as the glow-worm, possess very peculiar phosph.o.r.escent qualities.

_Phosph.o.r.escent_, having a phosphoric property, emitting peculiar light like phosphorus.

What is a.r.s.enic?

A heavy metallic substance, very volatile, and highly inflammable; so caustic or corrosive to animals, as to become a violent poison in all its states. In its metallic state it is used in several of the arts: it is employed in the manufacture of fact.i.tious metals: it is of use to the dyer in forming some of his colors; and for that purpose is generally combined with pota.s.sa. It is used in the making of small shot, and also in the manufacture of gla.s.s, to which it gives transparency; in whitening copper; in calico printing; in the preparation of colors for the painter; and in the working of platina, and some other metals, to render them more easily fusible.

_Caustic_, dry, burning.

_Corrosive_, apt to corrode, to eat away, to penetrate.

How is the white powdered a.r.s.enic prepared?

By submitting the ore to a strong heat in a peculiar kind of furnace; this produces a dark grey powder, which is again heated in close iron vessels; this separates it from its impurities, and the a.r.s.enic is obtained in thick, solid ma.s.ses; these, by exposure to the air, fall into a fine, white powder.

From what is the word a.r.s.enic derived?

From a Greek word, signifying _masculine_--powerful (as a poison).

a.r.s.enic is dug out of mines in Saxony, near Goslar; in Bohemia; in England, in the Mendip Hills, in great quant.i.ties. It has so strong a corrosive quality as sometimes to burn the hands and feet of the miners; it is a deadly poison for all known animals. This poisonous mineral is not found native in its perfect form, being generally united with metallic ores.

What do you mean by Gems?

The word gem is used as a common name for all precious stones or jewels; they consist of the siliceous earths; and are much valued for their l.u.s.tre, transparency, color, hardness, and rarity. There are many different kinds of precious stones, each distinguished by its peculiar character.

How are they divided?

Into the pellucid gems, which are of great l.u.s.tre, and extremely hard, as the diamond; the semi-pellucid, those which are not so transparent, but yet of great beauty; those of one color, as the emerald or turquois; and those variegated or veined with different colors. Gems are sometimes found of regular shapes, with a natural polish, near the beds of rivers after great rains; these are of the pebble kind.

Sometimes they are found of irregular shapes, with a rough coat, in mines and the clefts of rocks. Pearls, though not stones, are also ranked among the number of gems.

_Pellucid_, clear as a drop of water.

_Semi-pellucid_, half pellucid.

Describe the Diamond.

The diamond is a precious stone, the first in rank of all the gems, and valued for its beautiful l.u.s.tre; it is the hardest of all stones, as well as the most valuable. The most esteemed are colorless. A diamond in its natural state as it comes out of the mine, and before it is cut, is called rough, because it has no brilliancy, but is covered with an earthy crust. The diamond is the Adamant of the ancients; hence the expression "hard as adamant," from its being the hardest substance in nature. The cutting of diamonds is a work of labor, and requires great skill; the polishing is performed by a mill of simple construction.

Where are they mostly found?

In yellow ochreous earths; in mines; and likewise in torrents, which have torn them from their beds. In former times, all the diamonds that were known were brought from the famous mines of Golconda, in Hindostan; the islands of Molucca and Borneo have also produced many valuable stones. The diamond mines of Golconda are now so exhausted, that they are not thought worth the expense of working; these gems are now brought chiefly from Brazil, in South America.