METALS ; METALLURGY. The metals form a numerous and highly important class of simple or elementary bodies. They amount in number to upwards of forty. They are; given alphabetically, as antimony, arsenic, barium, bismuth, cadmium, calcium, cerium, chromium, cobalt, columbium, copper, gulcinium, gold, iridium, iron, latanium, lead, lithium, magnesium, manganese, mercury, molybden, nickel, osmium, palladium, platina, potassium, rhodium, silver, sodium, strontium, tellurium, Chorine; tin,-titanium, tungsten, ura nium, vanadium, yttrium, zinc, zirconium. Some chemists rank selenium and silicium also among the metals, and a few newly discovered metals are now undergoing examination.
With the exception of mercury all metals are solid at the usual temperature of the air, and the colour of most of them is grayish white. The lustre of metals is great and pecu liar, and is well known by the name of the metallic lustre; they differ however very con siderably in the degreo in which they possess this property. When reduced to a state of minute division, the metallic lustre is lost but the colour remains. The metals are generally reckoned perfectly opaque, even when reduced to thin leaves; but it is found that gold-leaf which is part of an inch thick, suffers light to pass through it, and it has a green colour ; it is therefore extremely probable that all metals, if they could be rendered equally thin, would also be translucent. There are some metals, such as lead, tin, copper, and iron, which, when rubbed, emit a peculiar and disagreeable smell; and others, such as ar senic: and antimony, which emit an odour when heated. All the metals are heavier than water, except sodium and potassium. num is the heaviest. About one half of them are ductile or malleable, and the other half brittle. Gold is the most ductile and the most malleable, iron is the most tenacious, and titanium the hardest, in their native state. The elasticity and sonorousness of metals are generally associated with their degree of hard ness. Thero are not however any metals which are by themselves either very elastic or sono roes ; but there are alloys which possess these properties in a high degree, as for example those of copper and tin.
Metals are sometimes lamellar, sometimes granular, and frequently crystalline : indeed, some of them, and more especially copper, occur crystallised in the form of the cube and its varieties. Bismuth is a metal which may be artificially crystallised in cubes with great facility.
No particular effect has been attributed to the agency of light upon metals. The metals are good conductors of heat; some of them rank in the following order in this respect— gold, silver, platina, copper, iron, zinc, tin, lead. Their capacity for heat ranges them in a different order, bismuth and lead taking the lead. Immediately that heat pervades the metals, and before it fuses them, it expands them in all directions. This dilatation is
different in different metals ; it varies also in the same metal with every degree of the ther mometric scale ; but from the freezing to the boiling point of water it may however be re garded as nearly constant. The fusing point of metals varies extremely. [FREEZING ; MELTING.] Some metals are volatilised at moderate de grees of heat : among these are mercury, cadmium, arsenic, tellurium, zinc, potassium, and sodium ; but there are others which may be exposed to the most intense heat of a wind furnace without being at all vaporised.
The relative conducting powers of the prin• cipal metals for electricity are as follow : copper, gold, silver, zinc, platina, iron, tin, lead, mercury, potassium. Each of the follow ing metals is positive with relation to those which follow it:—zinc, lead, tin, iron, anti mony, bismuth, copper, mercury, silver, gold, tellurium, palladium, platina. There are two metals only which are capable of being ren dered permanently magnetic, namely, iron and nickel ; the former of these only is met with possessing this property in nature ; it is an oxide of iron, and commonly called the loadstone. Most of the metals combine with each other and form compounds differing very materially in properties from their constituent metals. [ALLOYS.] All metals smite with ox ygen, but with different degrees of facility and 'affinity ; most of them combine with more than one proportion of oxygen and some of them with several proportions. A few of these compounds form acids, but most of them ox ides. Hydrogen, chlorine, bromine, sulphur, iodine, and plisphorus, all combine with some or other of the metals. Some metals, as potassium, sodium, and manganese, decom• pose water even at common temperatures, combining with its oxygen and evolving the hydrogen; others, as iron and zinc, require to be strongly heated, or the presence of an acid, to effect this decomposition.
Although most metals are dissolved by acids, yet platina and gold are exceptions to it, these and some others requiring chlorine, and generally in the nascent state called aqua regia.
Metallurgy, or the separation of metals from their ores and from other compounds, varies in its processes according to the metal ; for which see COPPER, GOLD, IRON, Lunn, &e. The working of metals into useful forms con stitutes the basis of such numberless mechan ical arts that we cannot here even enumerate them; the principal among them will be found under their proper headings.
In relation to commerce, the metals form a very important section of our Exports and Imports. Among our Imports for 1819 and 1850 we find the following :— In respect to Exhibitions of Manutactures, such as that which so largely attracts public attention in 1851, the metals form by far the most bulky of the specimens.