The Republican. [volume] (Oakland, Md.) 1877-current, 1889-07-13
FACTS ABOUT METALS.
The Degree of Heat Required to Melt
Platinum, Gold and Silver.


| Platinum, Gold and Silver.
Platinum, the densest of the ordinary
metals. possesses a very high point of
fusion. The metal fuses only in the
heat of the oxyhydrogen blow-pipe.
When in the state of very fine wire il
may be melted into small globules by
the heat of an ordinary mouth blow
pipe, and is quite readily fused in very
small quantities by the aid of hot
blast supplied to an ordinary Bunson
gas flame. Platinum belongs to the
class Of metals which soften before
they attain perfect fluidity, This Pc
culiarity permits the uniting of plati-
mum surfaces without the use of solder,
and enables the finely divided metal.
technically termed the metallic
SPONGE" to be wrought into solid
and compact bar. Platinum is not
volatile at any temperature we are
able to command, though doubtless at
sufficiently high temperatures it, in
common with all substances, would be
vaporized. Platinum does not COM
bine directly with oxygen, and there
fore does not waste during the process
of melting.
Gold melts at about 2,016o to 2,190o
F., according to different authorities.
1t is affected neither by water nor air
at any temperature, and it is not at
tackled by ordinary acid. 1t is the most
malleable of all the metals, and may be
beaten into sheets OF surprising won
derful thinness. Its very great mallea-
bility renders it unfit for use for jewelry
or for coinage until its hardness and
consequent durability are increased by
alloying it with silver or copper. Ex-
posed to the heat of the oXyhydrogen
blow-pipe it is known to be vaporized;
and it was formerly supposed that it
was not volatile at flower temperatures,
but the researches of Napier and
Makins show that volatilization occurs
at temperatures of an ordinary muffle
furnace when alloys of gold and silver
are cupelled with lead. An analysis of
deposits taken from the chimney of
small reverbatory furnace, in daily use
for cupelling gold for months. showed
fourteen per cent. of silver and IL
grains OF gold for every eight ounces
of silver. Still, after the destruction of
a quantity of jewelry by fire, a great
proportion of the gold should be re-
coverable, since but small quantity,
il any, would be volatilized. Gold will
alloy readily with nearly all other
metals. Its alloys with silver and
copper are, however, the only ones
employed in the arts.
Lead melts at about $500 F.
Unlike gold, it combines readily with
the oxygen of the air, forming various
oxides, mainly litharge, product of
the direct oxidation of the metal.
When melted and exposed to the
atmosphere it absorbs oxygen very
rapidly; so that, unless caution be ex-
ercised in melting, it is apt to waste
from direct oxidation, and especially
from the fact that at a white heat it
boils and volatilizes. When in very
finely divided state. metallic lead COM
Dimes so rapidly with oxygen that it
takes fire while falling through the air,
and burns with livid flash. This
metal possesses the valuable property
Of welding in .Ae cold, provided the
surfaces joined are clean and free from
oxide. Lead forms alloys with many
of the metals. Many of its alloys are
of great value. 1t alloys but imper-
fectly with copper, zinc, nickel and
iron, though by introducing third
metal having an affinity for both the
others, this difficulty may be overcome.
The following are some of the impor-
tant alloys:
Solders-Lead alleged with tin forms
various soldiers. Fine solder contains
two parts of tin and two of lead; COM
mon solder, equal parts of tin and lead;
coarse solder contains two parts of lead
and one of tin; plumbers solder is the
same as the last.
Pewter is composed of eighty parts
of lead and twenty parts of tin; but to
these copper, antimony or zinc is gen.
orally added. Lead alleged with tin
and bismuth forms variety of alloys
that are remarkable for their extraor-
binary low melting points. on which
account they are termed fusible metals.
Roses fusible alloys, formed of two
parts of bismuth, one of tin and one of
lead. melts at about 203 . F., or below
the boiling point Of water. Britannia
metal is an alloy of equal parts of
brass, tin, anthony and bismuth.
Silver melts at about 1873 . F., or at
about bright-red heat. Like gold, it
is not attacked by air or moisture, the
tarnish which appears on silverware
being caused by gases in the air.
Blacksmith and Wheelwright.