SECONDARY PLATINUM.
Large
quantities of platinum, probably amounting to at least one-third of the
metal produced and imported into this country, are recovered as scrap
or secondary platinum. It is practically impossible to obtain from the
few refineries exact data as to the quantity of this secondary metal
recovered.
CONSUMPTION OF PLATINUM IN THE UNITED STATES.
It
is not possible, owing to the peculiar conditions obtaining in the
platinum industry, to obtain statements of stocks in hand at the
various refineries, and the exact consumption can therefore not be
stated. The apparent consumption is measured by the approximate
production of refined metal in the United States, which was about
29,140 fine ounces, added to the imports of bars, unmanufactured metal,
and manufactured products, amounting to approximately 91,600 fine
ounces. The total apparent consumption was, therefore, 120,740 fine
ounces, which is about one-half of the world's production of refined
platinum. This estimate takes no account of the secondary platmum
recovered from scrap.
THE PLATINUM METALS.1
Six
closely related metals are usually referred to as the "platinum group."
They are platinum, iridium, osmium, ruthenium, rhodium, and palladium.
According to their atomic weights, they fall into two groups, the first
including ruthenium (101.7), rhodium (103), and palladium (107); the
second group including osmium (191), iridium (193.1), and platinum
(194.9). The atomic weight of gold (197.2) is close to that of
platinum. In specific gravity the purified metals range as follows:
Osmium, 22.48; iridium, 22.42; platinum, 21.48; ruthenium, 12.26;
rhodium 12.1; palladium, 11.4.
In
fusibility the order is as follows: Osmium is the most refractory of
the metals, melting considerably above 2,000° C; ruthenium, iridium,
and rhodium follow in order; the fusion point of iridium is from 2,150°
to 2,250° C. At 1,100° C. iridium begins to oxidize to a purple oxide.
The melting point of platinum is 1,779° C. Palladium is the most
fusible and melts at about 1,549° C., or at about the same temperature
as wrought iron.
Platinum.—The
mineral called platinum is really an alloy of platinum, iridium,
rhodium, palladium, and often osmium, with varying amounts of iron,
copper, and gold. It is usually found as small nuggets, scales, and
rounded or irregular grains; its color is steel gray. The specific
gravity of the crude platinum varies from 14 to 19. The
p
ercentage of platinum
varies also within wide limits, but is generally from 70 to 85 per
cent. The native platinum may be strongly magnetic or comparatively
inert. The metal platinum is of grayish-white color and is hard,
malleable, and ductile.
Iridium.—Iridium
is generally present in crude platinum sand in alloy with osmium, as
iridosmine, or more rarely in alloy with platinum as native metal. In
its manufacture from crude platinum it is obtained as a sponge, which
is then melted with the addition of a
i The following paragraphs are in part taken from Kemp, J. F., Geological relations and distribution of platinum and associated metals: Bull. U. S. Geol. Survey No. 193,1902.
