Manufactured
platinum exhibits in general the same physical properties as the crude
metal. Its specific gravity is increased to 19.7 for melted metal and
to 21.23 for hammered ware. Pure platinum is quite soft, very
malleable, and can be drawn into the finest of wire. Its melting point,
as already stated, is 1,750° C. Platinum forms readily fusible alloys
with lead, tin, bismuth, antimony, and zinc; therefore these metals, or
their compounds, should never be treated in platinum vessels. Heated
platinum ware is also attacked by free sulphur, selenium, iodine,
arsenic, and phosphorus.
Iridium
is the hardest known metal. It has a lustrous white color and is about
20 per cent heavier than pure gold, haying a specific gravity of 22.4.
It is somewhat malleable when hot, but brittle when cold. It fuses at
1,950° C, and, when pure, is insolubie even in aqua regia.
Osmium
is the heaviest of the known metals, having a specific gravity of 22.47
to 22.5. It is also practically infusible, with a melting point in the
vicinity of 2,500° C. It is easily oxidized when heated to the volatile tetroxide (OsO4).
Palladium
has a specific gravity of 11.4, and approaches steel in hardness. Its
melting point, 1,500° C, is the lowest of any of the platinum metals.
It is more malleable than platinum, can be welded much more easily, and
has a brilliant metallic luster. The one notable property of palladium
is its peculiar power to absorb hydrogen, first forming palladium
hydride (Pd2H), which in turn absorbs further hydrogen. At
ordinary temperatures palladium foils will absorb about 370 volumes of
hydrogen, and if the foil be heated to 100° C. the quantity of hydrogen
absorbed will be increased to 650 volumes. Palladium sponge is even
more active, and at 100° C. will absorb nearly 1,000 times its volume
of hydrogen.a
Rhodium
is steel gray in color, has a specific gravity of 12.1; it fuses at
2,000° C, and is less malleable and ductile than platinum. It oxidizes
at a red heat, but when pure is insoluble in all acids.
Ruthenium
is a hard and brittle metal, haying a specific gravity of 11.4. It is
almost as infusible as osmium, melting at about 2,500° C. It oxidizes
slowly at ordinary temperature and very rapidly when heated, forming
ruthenic oxide (Ru2O3)
PRODUCTION.
The
production of platinum in 1905 is reported as 818 ounces, valued at
$5,320, as against 200 ounces, valued at $4,160, in 1904.
IMPORTS.
The
imports of platinum during 1905 were valued at 82,173,263, as against
81,879,155 in 1904, an increase in value of 8294,108. The imports in
1905 were distributed as follows: Unmanufactured, 1,598 pounds
(8296,883); ingots, bar sheets, and wire, 6,228 pounds (81,688,224);
vases, retorts, and other apparatus, vessels and parts thereof for
chemical uses, $186,742; manufactures of, not specially provided for,
§1,414. The imports in 1903 were valued at $2,055,938, in 1902 at
$1,987,980, and in 1901 at $1,695,895.
Considering
the increased demand for platinum, the gain in importation is slight,
but if the high price and scarcity of the metal be taken into account
the wonder is that there was not a large decrease in the quantity
imported.
USES.
On
account of its many valuable physical and chemical properties platinum
has a diversity of uses exceeded by no other metal. Its employment is
of course restricted by its scarcity and high price, but to many of the
arts and sciences it is an indispensable adjunct. The principal
consumption of platinum is in the chemical and elec-
a Wharton, Joseph, Palladium: Proc. Am. Phil. Soc, vol. 43, No. 177.
