Man's physical universe

xanabras

METALLURGY 641

Aluminum and its alloys make possible modern transportation

alone.

by the all-metal airplane, the streamlined train, and trucks, where

dead weight must be eliminated. It is even finding application in the

construction of bridges, booms, and other structures where lightness

is at a premium.

Aluminum is now meeting with some competition from other light

metals. Magnesium, which is lighter than aluminum, is now produced

at prices which enable it to compete with aluminum for some

purposes. Magnesium metal is used not only in making light, strong

alloys but also in producing flashlights and flares; for example,

320,000-candle-power flares lasting ten minutes enable airmen to aim

bombs or take pictures at night.

Beryllium is the other contender among the light metals. It is a

very light metal; but, unfortunately, large deposits are not available,

and it is expensive to extract from its ores. However, it is a valuable

alloying element in small amounts in other metals; a good example is

beryllium bronze.

Other Metals Are Finding Fields of Usefulness.

Tungsten is a metal with many valuable properties.

It is very hard,

is insoluble in acids, and has a very high melting-point. Because of

its high melting-point and low electrical resistance, it is used as an

electric-light filament.

Platinum is a useful metal, most of which is wasted in making

jewelry, so that its price is very high. Many substitutes for platinum

are now available.

The other members of the platinum family, palladium,

rhodium, osmium, and iridium, are now used for many purposes

where a metal that will resist the action of other substances is

needed.

Nickel (the United States nickel coin is 75 per cent copper and

25 per cent nickel) is especially valuable in the preparation of alloys.

Nickel imparts toughness, heat resistance, and noncorrosive qualities

to other metals. Stainless steels have a high nickel content, while

monel metal is an alloy of nickel and copper. German silver is an

alloy of nickel, copper, and zinc.

Copper also plays a versatile role in alloys, but its most important

applications are in the electrical industry, because it is the most economical

electrical conductor.

Bismuth is used to prepare low-melting-point alloys. Metallic

barium has recently been produced as a commercial article. Pure

molybdenum is now used in the form of sheet, rod, and wire in the

electrical and radio industries.

Cerium, which, when alloyed with other

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