| IRON, | MERCURY, |
| COPPER, | NICKEL, |
| LEAD, | GOLD, |
| TIN, | SILVER, |
| ZINC, | PLATINUM. |
But in the state of oxide many are used which are seldom seen in the metallic state, such are the earths and alkalies; and for colors, and several other purposes, many other preparations are in use. The chief alloys, or compound metals in use, are, brass, made of copper and zinc; pewter, made of lead and tin; bell metal and gun metal, made of copper and tin; and solder, which is a kind of pewter, and made of the same metals; the silvering for looking-glasses is made of mercury and tin; the gold and silver used for coin are not pure metals, but alloyed with two parts of silver or copper to every twenty-two of the pure metal, and this forms the “standard” gold or silver. The gold used by jewellers has often a much greater proportion of alloy—for this name is given both to a compound metal and the cheaper metal made to combine with the more precious. The object gained by thus alloying the coinage, is that of rendering the metals harder, so that they shall not suffer much loss in wearing; thus a small quantity of copper mixed with either gold or silver, renders them both harder, although itself softer than either. The combination of certain metals forming alloys, is often not exactly the mean of their respective qualities, for instance, a small quantity of silver is sometimes fused with cast steel for penknife blades, and although the silver is itself much softer than the steel, yet the combination is found to be both closer in the grain and harder; it is known as silver-steel in commerce. Bismuth, although itself not very fusible, increases the fusibility of other metals; a combination of 2 parts tin, 3 lead, and 5 bismuth, forms a metal fusible by boiling water.
IRON.
NATIVE OXIDE OF IRON.
Iron stands first in usefulness of all the metals, for railways, bridges, ships, and a thousand other purposes; it can be both cast and wrought, having that peculiar property, the capability of being “welded,” that is to say, of softening while hot to such an extent that when two pieces are made white hot and laid together, a few blows of the hammer will cause them to unite into one piece, and it is by means of this most useful quality that large masses of wrought iron are produced, such, for instance, as anchors and cranks for steam-boats. This property of welding, and the abundance of the ores of iron, render it one of the most useful materials supplied by nature for the various purposes of manufacture. In combination with carbon it forms that hardly less useful article known by the name of steel.
Cast Iron has scarcely any of the metallic lustre, and is only fitted for solid work; it is brittle, like steel, without its elasticity, and is too soft and too porous to be made into any of the numerous tools and instruments for which steel is so eminently suitable. Cast iron contains many impurities, the chief of which are carbon, sulphur, and silica, got from the coke whilst being smelted in contact with it, and from the fluxes used in the process; it is coarse in grain, and much more fusible than wrought iron, which is iron in a nearly pure state and can be fused only by the very highest heat capable of being produced. Cast iron is converted into wrought or malleable iron by being re-melted and stirred for a long time in contact with the air, this process is called “puddling,” its object is to get rid of all the impurities (chiefly carbon and sulphur) which, by being brought into contact with the air at a high temperature, are said to be burnt out, that is to say, they combine with oxygen and form carbonic and sulphurous acids. After puddling, the iron is rolled or hammered out, folded up, and again extended, and as a general rule it may be said, the more this is continued the purer and softer is the iron.