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224 MECHANICAL DENTISTRY AND METALLURGY.
The Fusing Point of platiinim is al)()ve 3500 Fahrenheit,
to reach which, in the laboratory, it is necessary to employ
the oxy-h}-(lrogen l)lo\\-pipe.
Use for Dental Purposes.—Platinum, in mechanical
practice, is chiefly employed as a base for continuous-gum
work; as a coloring ingredient of porcelain; for pins fc^-
attaching mineral teeth; for backings, and dowels in crown-
and bridge-work; and, to a limited extent, in some of the
minor operations of the laboratory.
Solder for Platinum.—Pure gold is the only proper
solder for this metal.
Alloys of Platinum.— Platinum unites with most of the
base metals, forming alloys of variable degrees of hardness,
elasticity, brittleness, color, fusibility, etc., but their prac-
tical value to the dentist is not sufficient to justify a separate
description of their properties.
With gold, it forms a straws-colored alloy, the shade de-
pending on the quantity of gold added. Sili'cr hardens it.
the resulting alloy Ijeing unaffected by sulphur.
Platinoid Metals.—The platinoid metals, palladium,
iridium, osmium, rhodium, and ruthenium, are nati\-e con-
taminations, the alloys of these metals having a close gen-
eral resemblance to platinum.
Among the platinoid metals, palladium and iridium are
the only ones that have been used for dental purposes, and
these only to a limited extent.
Palladium (Symbol, Pd. Atomic weight, 106). is of a
steel-gray color, and when planished, is a brilliant, steel-
white metal, not liable to tarnish in the air. Though closely
resembling platinum, it may be readily distinguished from
the latter metal by the following tests : ( i ) It has little more
than one-half the density of platinum. (2) If a piece of
it is heated to redness, it assumes a bronze-blue shade, of
greater or less intensity, as it is cooled more or less slowly
224 MECHANICAL DENTISTRY AND METALLURGY.
The Fusing Point of platiinim is al)()ve 3500 Fahrenheit,
to reach which, in the laboratory, it is necessary to employ
the oxy-h}-(lrogen l)lo\\-pipe.
Use for Dental Purposes.—Platinum, in mechanical
practice, is chiefly employed as a base for continuous-gum
work; as a coloring ingredient of porcelain; for pins fc^-
attaching mineral teeth; for backings, and dowels in crown-
and bridge-work; and, to a limited extent, in some of the
minor operations of the laboratory.
Solder for Platinum.—Pure gold is the only proper
solder for this metal.
Alloys of Platinum.— Platinum unites with most of the
base metals, forming alloys of variable degrees of hardness,
elasticity, brittleness, color, fusibility, etc., but their prac-
tical value to the dentist is not sufficient to justify a separate
description of their properties.
With gold, it forms a straws-colored alloy, the shade de-
pending on the quantity of gold added. Sili'cr hardens it.
the resulting alloy Ijeing unaffected by sulphur.
Platinoid Metals.—The platinoid metals, palladium,
iridium, osmium, rhodium, and ruthenium, are nati\-e con-
taminations, the alloys of these metals having a close gen-
eral resemblance to platinum.
Among the platinoid metals, palladium and iridium are
the only ones that have been used for dental purposes, and
these only to a limited extent.
Palladium (Symbol, Pd. Atomic weight, 106). is of a
steel-gray color, and when planished, is a brilliant, steel-
white metal, not liable to tarnish in the air. Though closely
resembling platinum, it may be readily distinguished from
the latter metal by the following tests : ( i ) It has little more
than one-half the density of platinum. (2) If a piece of
it is heated to redness, it assumes a bronze-blue shade, of
greater or less intensity, as it is cooled more or less slowly
