COPPER AND ITS ALLOYS, BRASS, BRONZE, ETC.
Copper.—Copper is a very ductile and malleable metal, melting at a point somewhat lower than gold, but higher than silver. It is the best known conductor of electricity, weighs about nine times as much as water, is hard, elastic, tough, and of a density only less than that of iron. It is found nearly pure in various parts of the world, also in a number of ores, in small quantities in most soils, in seaweeds, and in the animal body. A compound of carbon with copper is sold as a pigment under the name of blue verditer, and from another com pound of copper Brunswick green is obtained. The blue and green verdi gris of commerce is made by the ac tion of acetic acid on oxide of copper. The blue vitriol used in dyeing is sul phate of copper.
Copper is used for ship sheathing and bolts, and for a great variety of wares. It is also largely used in transmitting electricity. It is exten sively used in various alloys, as brass, gun metal, bell metal, bronze, alu minum bronze, German silver, and others.
To Improve Copper Castings.—To 100 pounds of melted copper add 1 pound of pulverized cryolite, 41 ounces cf sugar of lead, and 1 pound of bo rax. Continue the heat 10 minutes be fore pouring the copper into the mold.
Feather-shot Copper.—To prepare, melt the copper and pour it in a thin stream in cold water.
Bean-shot Copper. — To prepare, pour melted copper in a thin stream in boiling water.
To Test for Copper.—To detect the presence of copper in liquids, put some of the liquid in kt wineglass and add a few drops of aqua ammonia. If copper is present, the liquid will turn blue. This is a useful test for tea, which sometimes is injured by being dried on copper.
It may also be applied to cider, yin egar, and the like, and likewise to pickles to make sure that they were not rendered poisonous by having been prepared in copper kettles.
To Whiten Copper. — Melt with 8 ounces of copper ounce of neutral arsenical salt in the presence of a mixture of burnt borax, charcoal dust, and prepared glass.
Or, for 1 pound of copper, mix 4 ounces of saltpeter and 4 ounces of arsenic in powder form, and melt in the crucible with gentle heat. Re
move, cool, and grind to powder. Add 1 ounces of Venetian borax and ounces of white tartar. Melt the mix ture and pour into an iron receiver. It will appear as clear crystals. Heat the copper in thin sheets six or seven times and quench in water. Melt the sheets and throw the above crys tals in small pieces into the melted copper, at intervals of 5 minutes, un til all have been thrown in. Continue the heat 15 minutes, and pour.
Brass. — This important alloy of copper and zinc is used for many pur poses, because it is easy to work and of an acceptable color. It is made by melting together copper and zinc in a crucible, the zinc being placed under the copper to prevent its pass ing off as a gas.
Or the zinc is first melted, and the copper added in strips or sheets. At first the copper is taken up rapidly, then more slowly. When all the cop per has been added, the alloy is cooled and remelted with charcoal, and more zinc or copper added to produce the desired quality of brass.
Or heat the copper in small grains or sheets with the oxide of zinc and charcoal.
Or heat the copper with calamine, a native ore of zinc, and charcoal. This was the ancient method.
There are different kinds of brass adapted to special uses according to composition. Common brass for cast ings contains about 70 parts of cop per and 30 parts of zinc. The addi tion of lead makes brass less ductile; tin makes it harder. Articles of brass may be cleaned by dipping them in nitric acid, and colored by lacquers of shellac and other resins in alcohol. Brass is harder than copper, is malle able, ductile, can be readily cast, rolled, stamped, and turned in the lathe. Next to iron it is the most im portant metal used in the arts.
Some of the various kinds of brass are as follows: Metal sheathing for ships (known as Muntz or yellow metal), copper, 50 to 62 parts; zinc, 38 to 50 parts. This is used to prevent decay from sea water in the wooden bottoms of ves sels and to keep off barnacles.