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250 MECHANICAL DENTISTRY AN U METALLIKGV.
tricity, and, in a greater or less degree, are ductile, malleable,
elastic, and sonorous. Some alloys, as brass and gong
metal, are usually ma]leal)le in the cold and 1)rittle when hot.
IMctals sometimes unite in atomic ratios, forming com-
pounds of definite or equivalent proportions of the compo-
nent metals, as certain alloys of copper and zinc, gold and
copper, gold and silver, mercurial alloys, etc., while, on the
other hand, many are formed in all proportions, like mix-
tures of salt and water.
Metals differ in respect to their affinity for each other,
and do not, therefore, alloy with ecjual facility; thus it is
difficult to unite silver and iron, but the former combines
readily with gold, copper, or lead.
The ductility of an alloy is, in general, less than that of
its constituent metals, and this difference is, in some in-
stances, remarkably prominent, as in the case of certain
alloys of copper and tin, already mentioned.
An alloy is generally harder than the mean hardness of
its components, a property which, when taken in connection
with their increased fusibility, gives to alloys peculiar value
in the formation of dies for stamping purposes. To the
rule stated, amalgams, or mercurial alloys, are cited as
exceptions.
The density of an alloy varies with the peculiar metals
composing- it, being g^enerally either greater or less than the
mean density of its several conponents.
Usual Methods of Producing Alloys.—Alloys are usually
formed by fusion, that is, by causing metals to unite by
fusing or melting them together. One metal is melted, and
then one or more metals, as the case may be, is added to it
sometimes in the fluid state, but more frequently in a solid.
It does not follow, however, that the metals will remain in
a proper state of mixture by simply fusing them together.
The difference in their specific gravity must frequently be
250 MECHANICAL DENTISTRY AN U METALLIKGV.
tricity, and, in a greater or less degree, are ductile, malleable,
elastic, and sonorous. Some alloys, as brass and gong
metal, are usually ma]leal)le in the cold and 1)rittle when hot.
IMctals sometimes unite in atomic ratios, forming com-
pounds of definite or equivalent proportions of the compo-
nent metals, as certain alloys of copper and zinc, gold and
copper, gold and silver, mercurial alloys, etc., while, on the
other hand, many are formed in all proportions, like mix-
tures of salt and water.
Metals differ in respect to their affinity for each other,
and do not, therefore, alloy with ecjual facility; thus it is
difficult to unite silver and iron, but the former combines
readily with gold, copper, or lead.
The ductility of an alloy is, in general, less than that of
its constituent metals, and this difference is, in some in-
stances, remarkably prominent, as in the case of certain
alloys of copper and tin, already mentioned.
An alloy is generally harder than the mean hardness of
its components, a property which, when taken in connection
with their increased fusibility, gives to alloys peculiar value
in the formation of dies for stamping purposes. To the
rule stated, amalgams, or mercurial alloys, are cited as
exceptions.
The density of an alloy varies with the peculiar metals
composing- it, being g^enerally either greater or less than the
mean density of its several conponents.
Usual Methods of Producing Alloys.—Alloys are usually
formed by fusion, that is, by causing metals to unite by
fusing or melting them together. One metal is melted, and
then one or more metals, as the case may be, is added to it
sometimes in the fluid state, but more frequently in a solid.
It does not follow, however, that the metals will remain in
a proper state of mixture by simply fusing them together.
The difference in their specific gravity must frequently be
