The oxides of lead are easily changed into glass, and unite with all the metals except gold and silver; on this account they are employed for separating other metals from these. This process is called cupellation. The mixed metal is put into a dish called a cupel, made of bone-ashes, and placed in a cupelling furnace; the lead is oxidized and vitrified, and sinks into the bone-ash cupel, carrying with it all the baser metals.

White lead, so much used in painting, is a compound of the yellow oxide and carbonic acid; or a carbonate of lead. It is made by exposing plates of pure lead to the warm vapour of vinegar. By this they are gradually corroded, and converted into a heavy white powder, which is white lead.

When the carbonate of lead is dissolved in distilled vinegar, a salt is obtained, which crystallizes, and is called commonly sugar of lead; more properly acetate of lead. All the salts of lead have a sweetish taste, and are of a poisonous quality.

The affinity of the muriatic acid (hydrochloric acid) for the oxides of lead is so great, that the latter decomposes all the combinations of this acid. They decompose the muriate of soda (common salt), and thus form muriate of lead, which, on fusion, affords mineral or patent yellow.

Sulphuric acid does not act on lead when cold; but dissolves it at a boiling heat, and forms sulphate of lead, which is insoluble in water.

Chromate of lead, or chromic acid and lead, is a very beautiful yellow pigment. It is found native in small quantities, but is now prepared largely by art. Lead is one of the most useful metals. It is much employed in covering houses, when made into thin sheets by casting or by milling. It is used also for water-pipes and cisterns, and for a variety

of well-known purposes. Its oxides are used in the manufactures of glass, and the glazings of earthenware; also as pigments. Preparations of lead are also used as external applications in diseases. The alloys of lead with tin form solder, and other alloys are employed in various arts,

ZINC.

This metal is chiefly procured from calamine, which is a hydrated oxide of zinc; and from blende, a sulphuret of zinc.

Zinc is a whitish metal of the colour of tin. It is slightly malleable when cold; but heated to between 200° and 300° it is very malleable, and has been manufactured into nails, drawn into wire, and made into sheets.

It is often known among workmen by the name of Spelter. It is easily fused, and is the most inflammable of the metals; thin leaves of it will take fire with the flame of a taper.

It is scarcely oxidized in the air at common temperatures, but is rapidly converted into oxide when kept melted in an open vessel. Its surface then becomes covered with a grey peilicle, which is oxide of zinc. When zinc is made red hot in an open vessel, it takes fire and burns with a brilliant flame, sending off white flakes of oxide. These have been called flowers of zinc.

Zinc decomposes water very slowly when cold; but with great rapidity when the vapour of water is brought into contact with it ignited.

Zinc dissolves very readily in diluted sulphurie acid; forming thus sulphate of zinc, or white vitriol. During this solution, a great quantity of hydrogen

gas is disengaged, and this is one of the best modes of procuring that gas.

The nitric and muriatic acids also act upon zinc. Zinc combines with phosphorus and sulphur.

It can be alloyed with most of the other metals. With copper, it forms brass.

ANTIMONY.

Antimony is rarely found native. It is procured from an ore called crude antimony, which is a sulphuret of antimony.

Antimony is of a silvery white colour. It is so brittle, that it may be pulverised in a mortar; and its interior texture appears to be scaly or lamellar. It requires 800° to fuse it. It does not change in the air, but when kept in fusion at a red heat, it emits white fumes, consisting of an oxide formerly called flowers of antimony.

There are two oxides of antimony. The protoxide is procured by precipitating the muriate of antimony by potash. It is of a grey colour. The peroxide is formed by causing the nitric acid to act upon the metal, or by collecting the fumes already mentioned as the flowers of antimony. It is white. The oxides of antimony are very valuable medicines. Tartrate of potash and antimony form emetic tartar. James's powder is composed of phosphate of lime and antimony. Kermes's mineral is made from sulphuret of antimony by potash.

Antimony is also used in printers' types; and in specula for telescopes. The sulphuret has been used for staining hair black.

BISMUTH.

Bismuth is found native, and also combined with sulphur and arsenic.

It is of a reddish white colour, brittle, and easily fusible. It is not quite so hard as copper. It is not oxidated by water; it tarnishes in the air, but does not undergo any other change. Kept melted in an open vessel, its surface becomes covered with a dark grey pellicle, which is renewed till the whole is converted into oxide.

The oxide of bismuth is a yellow powder. When strongly heated it melts and becomes darker coloured.

Bismuth dissolved in the nitric acid, affords a white powder, if water be added to the solution. This is the magistry of bismuth, or pearl white, which has been used as a cosmetic, but very improperly, as it is apt to turn black by sulphuretted hydrogen. Bismuth dissolved by the acetic acid forms a sympathetic ink. The characters written with it are invisible, until they are exposed to sulphuretted hydrogen, when they appear black.

Bismuth alloys with all the metals, and has the property of giving them great fusibility. If eight parts of bismuth, five of lead, and three of tin be fused together, they form what is called the fusible metal, which melts in boiling water. On this account bismuth enters into the composition of some of the soft solders.

It has also the property of rendering gold extremely brittle.

ARSENIC.

Arsenic, the poisonous effects of which are so well known, is a metallic substance, sometimes

found native, but oftener combined with sulphur. The sulphuret of arsenic is called orpiment.

Arsenic is frequently mixed in metallic ores, and is driven off by heat. It is known by its' peculiar smell, like garlic.

The colour of metallic arsenic is grey; it is very brittle. It soon loses its metallic lustre in the air, and becomes black. The oxides of arsenic have acid properties. There are two: the white oxide of arsenic is called arsenious acid. It is highly poisonous. It is soluble in water. It reddens vegetable blues. It is of a white colour, is semitransparent, and brittle. Its taste is acrid, with a nauseous sweetness. The best way of getting rid of its action as a poison, when taken into the stomach, is to produce vomiting and purging.

Arsenic acid is a white deliquescent substance, of a sour taste, obtained by distilling nitric acid off metallic arsenic. It forms salts with several of the metals. Arseniate of iron crystallizes in cubes of a green colour. The arseniates of copper are among the most beautiful minerals. The alloys of arsenic with some of the metals are used for some. purposes. It is mixed with lead to assist its granulation in making small shot. It is also used in making flint glass, and in calico-printing.

NICKEL.

Nickel is a rare metal. It is white, much resembling silver; and possesses, like iron, the magnetic property. It is not easily fused, and it is malleable. It is rather softer than iron, and soon tarnishes in the air. It is found native, and combined with arsenic.

Nickel dissolves in the acids, and its salts are distinguished by their fine green colour.