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252 MECHANICAL DENTISTRY AND METALLURGY.

and the theory of the subject, point to the conclusion that
the eutectic alloy is not generally a compound, and hence
should not have a formula. Further research, however, is
necessary before any definite conclusion on this point can be
generally accepted. The tendency of the constituents to
separate on cooling is knoAvn as liquidation, and is a matter
of importance in casting alloys for industrial purjjoses. In
some instances where liquidation has taken place a more
homogeneous alloy may be obtained by breaking up the
ingot and remelting.*
The Fusing Point.—It is impossible to predict with cer-
tainty the melting point of an alloy from that of its separate
constituents, but, generally, the fusibility of the alloy is
increased, sometimes in a most remarkable degree. The
alloy of 5 parts of bismuth, 3 of lead, and 2 of tin is a
striking example of this fact, this compound melting at
197°, while the mean melting point of its constituent is
514°. Silver solder is also a familiar illustration of the
influence of alloying on the fusibility of metals ; copper,
melting at 1996°, and silver at 1873°, when combined fuse
at a heat much below that required to melt silver, the more
fusible component of the alloy. Examples might be mul-
tiplied, but it will be sufificient to add that, in general,
inefallic alloys melt at a lozucr Jicat than is required to fuse
tJie most refractory or infusible component, and sometimes
tJian the most fusible ingredient.
The color of an alloy cannot, in general, be inferred from
that of component metals ; thus it would be conjectured that
copper would be rendered very much paler by adding to it
zinc in considerable quantities, but the fallacy of such an
inference is at once shown by an examination of some of
the richlooking gold-colored varieties of brass, as Prince's
metal, pinchbeck, and similor, composed each of nearly ec[ual
* Smith's Metallurgy.