Page images
PDF
EPUB

XLIII. THORIUM.

This metal is derived from an earth, thorina, found in an extremely scarce mineral obtained from Norway. earth itself is an oxide of the metal, and the metallic base is derived from it by a process similar to that pursued in the case of aluminum. The metal is obtained as a dark heavy powder, which, when pressed by the burnisher, exhibits a metallic lustre, and an iron-gray colour. It is not oxidated by water, whether hot or cold. When gently heated in the open air it takes fire, and burns with amazing brilliancy. The result is thorina, which is as white as snow, and exhibits no trace of fusion. The combining weight of thorium has been calculated at 59.83.

XLIV. ZIRCONIUM.

Zirconium, so named from zircon, a precious stone, derived from the Island of Ceylon, is found in the zircon, the hyacinth, and three other rare minerals. It may be procured by heating potassium with the double fluoride of potassium and zirconium. It is obtained as a black powder, which may be compressed by the burnisher into thin shining scales of a dark gray colour and faint metallic lustre. Its particles adhere so slightly, that it is incapable of conducting electricity. It is not oxidated by being boiled in water. When heated in the open air, it takes fire at a moderate temperature, burns brightly, and is converted into zirconia. Its combining weight is calculated at 33.67.

XLV. ALUMINUM.

Aluminum is derived from the oxide, alumina, a substance, which, along with silica, forms the greater part of the solid crust of the globe. The oxide forms the basis of numerous mineral species, generally as a base, but often as an acid, and some of them amongst the most beautiful of the mineral kingdom, and only surpassed, if they can be said to be surpassed, by the diamond. The metal itself may be obtained by heating the oxide to whiteness, and passing through it the vapour of potassium. But it is best obtained by the action of potassium on chloride of aluminum. Minute pieces of potassium are put into a crucible of porcelain or platinum, over which is placed a quantity of anhydrous chloride of aluminum, containing as nearly as possible, the quantity of chlorine equivalent to the potassium employed. The lid of the crucible being fixed down, the crucible is heated. At the moment of decomposition, an intense heat is evolved, which raises the crucible to redness in an instant. The matter within the crucible is fused, and when quite cold, it is plunged into a vessel of water. The potassa is dissolved, and there is found in the solution, a gray powder, which, when closely viewed in the sunshine, is seen to consist of minute metallic scales. These being washed in cold water are filtered and dried. When this scaly powder is pressed by a burnisher on a hard substance, as steel, or in an agate mortar, the particles are partially welded together, and form a substance which strongly reflects the light. Aluminum thus obtained, resembles the noble metal platinum under the same circumstances. In this state of minute division, it is a non-conductor of electricity, but becomes a conductor when fused.

Aluminum requires an intense heat to melt it. It is not liquefied at the temperature at which cast-iron melts, and its precise point of fusion is unknown. When heated in the open air it takes fire, and burns with a brilliant light, producing alumina ; and if the combustion be in oxygen gas, the flame is splendid, and the heat excited so intense as partially to fuse the earth, although one of the least fusible substances in nature. When heated in chlorine gas, it in like manner takes fire, and is converted into chloride of aluminum.

Aluminum, although it has a powerful affinity for oxygen, is not readily acted upon by exposure to the air. It is not oxidated by water at common temperatures; but when the water is raised to the boiling state, a slight oxidation is seen to commence.

The combining weight of aluminum is generally estimated at 13.72 ; but some reckon it double, and others reduce it to 10.

The most important of the compounds of aluminum, and one of the most generally diffused products of the mineral kingdom, is the oxide. This substance is hard, and infusible in an extraordinary degree. It is found nearly pure in the class of gems comprehended under the term sapphire, namely, the sapphire proper or blue sapphire, the ruby, the topaz, the emerald, the amethyst. It is itself obtained as a white powder, destitute of taste and smell, and only fusible at an intense temperature.

It is insoluble in water, although under certain conditions it combines with water, forming hydrates. These hydrates are with difficulty soluble in water, and the solution, when condensed, produces a gelatinous mass, like hydrate of silicium under the same circumstances. Alumina unites with acids as a base, forming salts, though it does not perfectly neutralize them, but it has likewise feeble acid powers combining with earthy

and alkaline bases. In the feebleness of its acid properties it resembles silica, as it does likewise in its external characters, in its infusibility, in its insolubility in water (with the power, however, of combining with that body), and in the hardness which it communicates to the minerals in which it exists.

Silica and alumina exist associated together throughout the entire mineral kingdom. They form the basis of what are termed clays, in which the silica stands to the alumina somewhat in the relation of an acid to a base. They form the bases, further, of all the larger masses of mountain rocks, and great mineral deposites, along with magnesia, lime, and the other alkaline earths and alkalies, together with the oxides of iron and other substances. It is not without seeming reason that the ancients reckoned earth one of the pristine elements of nature. They supposed all metals and precious stones to be derived from it, all plants and even animals; and science may yet admit, that metals and precious stones are derived from the elements which constitute earth, and that the matter of plants and animals has no other origin.

XLVI. YTTRIUM.

This substance is the metallic base of an earth obtained in 1794, from a solitary mineral species found in the quarry of Ytterby, in Sweden, and since discovered in a few other minerals equally rare. The earth is an oxide, from which the metallic base is derived by the same process which has been described in the case of aluminum, that is, the chloride of the metal is subjected to the action of potassium. The metal is obtained in the state of minute scales, having the colour of iron, and a lustre much inferior to aluminum. It is brittle, whereas aluminum and glucinum are ductile. At common temperatures it does not become oxidated in the air or in water. When heated to redness it takes fire, and is converted into yttria, and in oxygen gas the combination takes place with surpassing splendour. Its combining weight is estimated at 32.25, though considerable doubt exists as to the true proportion.

« PreviousContinue »