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ALT.OYS IN PROCESS OF COMPOUNDING. :53

parts of copper and zinc ; and Manheim gold, compounded
of parts copper and i of zinc.
3
The se\-eral properties peculiar to alloys enhances the
value of many metals for industrial purposes. Copper,
taken as an instance, has a fusing" point too high for
ordinary casting, and is too tough for turning, but with the
addition of a little zinc it becomes harder and more elastic;
the fusing point is lowered so much that castings may be
made, and it may be readily turned in a lathe.
Composition of the more familiar alloys, though variable,
is about as follows

Gold Coin. Gold Plate and Jewelry.
Gold 90 Gold So
Copper 10 Copper 20

Silver Coin. Silver Jewelry-.
Silver 90 Silver 80
Copper ID Copper 20
Aluminium Bronze. Pinchbeck.
Copper 90 Copper 90
Aluminium 10 Zinc 10
Brass. Bronze Cannon.
Copper 70 Copper 90
Zinc 30 Tin 10

German Silver. Babbitt Metal.
Copper 45 Copper 2
Zinc 30 Antimony 3
Nickel 25 Tin 12
Pewter. Plumber's Solder.
Tin . 92 Tin (>7
Lead Lead 33
The affinity of an alloy for oxygen is greater than that
of the separate metals, a phenomenon that is ascribed by
some to the increase of affinity for oxygen which results
from the tendency of one of the oxids to combine with the
other by others it is attributed to galvanic action. Accord-
;