Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish platina, a diminutive of plata "silver".
Platinum is a member of
the platinum group of elements and group 10 of the periodic
table of elements. It has six naturally occurring isotopes. It is one of
the rarer elements in Earth's crust, with an average abundance of
approximately 5 μg/kg. It occurs in some nickel and copper ores along with
some native deposits, mostly in South Africa, which accounts for
80% of the world production. Because of its scarcity in Earth's crust, only a
few hundred tonnes are produced annually, and given its important uses, it is
highly valuable and is a major precious metal commodity.
Platinum is one of
the least reactive metals. It has remarkable resistance to corrosion,
even at high temperatures, and is therefore considered a noble metal.
Consequently, platinum is often found chemically uncombined as native platinum.
Because it occurs naturally in the alluvial sands of various rivers,
it was first used by pre-Columbian South American natives to produce
artifacts. It was referenced in European writings as early as the 16th century,
but it was not until Antonio de Ulloa published a report on a new
metal of Colombian origin in 1748 that it began to be investigated by
scientists.
Platinum is used
in catalytic converters, laboratory equipment, electrical contacts
and electrodes, platinum resistance thermometers, dentistry equipment,
and jewelry. Platinum is used in the glass industry to manipulate molten
glass which does not "wet" platinum. As a heavy metal, it leads
to health problems upon exposure to its salts; but due to its corrosion
resistance, metallic platinum has not been linked to adverse health effects. Compounds containing platinum, such as cisplatin, oxaliplatin and carboplatin,
are applied in chemotherapy against certain types of cancer.
Pure platinum is less
expensive than pure gold, having been so continuously since 2015. In early 2021, the value of platinum ranged
from US$1,055 to US$1,320 per troy ounce.
History of Platinum
Early uses
Archaeologists have
discovered traces of platinum in the gold used in ancient Egyptian burials as
early as 1200 BC. For example, a small box from burial of Shepenupet II was
found to be decorated with gold-platinum hieroglyphics. However, the extent of early Egyptians'
knowledge of the metal is unclear. It is quite possible they did not recognize
there was platinum in their gold.
The metal was used
by pre-Columbian Americans near modern-day Esmeralda, Ecuador to
produce artifacts of a white gold-platinum alloy. Archeologists usually
associate the tradition of platinum-working in South America with the La
Tolita Culture (circa 600 BC – AD 200), but precise dates and location is
difficult, as most platinum artifacts from the area were bought secondhand
through the antiquities trade rather than obtained by direct
archeological excavation. To work the
metal, they would combine gold and platinum powders by sintering. The
resulting gold–platinum alloy would then be soft enough to shape with tools. The platinum used in such objects was not the
pure element, but rather a naturally occurring mixture of the platinum
group metals, with small amounts of palladium, rhodium, and iridium.
European discovery
The first European
reference to platinum appears in 1557 in the writings of the Italian humanist Julius
Caesar Scaliger as a description of an unknown noble metal found between Darién and
Mexico, "which no fire nor any Spanish artifice has yet been able to
liquefy". From their first
encounters with platinum, the Spanish generally saw the metal as a kind of
impurity in gold, and it was treated as such. It was often simply thrown away,
and there was an official decree forbidding the adulteration of gold
with platinum impurities.
In 1735, Antonio
de Ulloa and Jorge Juan y Santacilia saw Native Americans mining
platinum while the Spaniards were travelling through Colombia and Peru for
eight years. Ulloa and Juan found mines with the whitish metal nuggets and took
them home to Spain. Antonio de Ulloa returned to Spain and established the
first mineralogy lab in Spain and was the first to systematically study
platinum, which was in 1748. His historical account of the expedition included
a description of platinum as being neither separable nor calcinable. Ulloa
also anticipated the discovery of platinum mines. After publishing the report
in 1748, Ulloa did not continue to investigate the new metal. In 1758, he was
sent to superintend mercury mining operations in Huancavelica.
In 1741, Charles Wood, a
British metallurgist, found various samples of Colombian platinum in Jamaica,
which he sent to William Brownrigg for further investigation.
In 1750, after studying
the platinum sent to him by Wood, Brownrigg presented a detailed account of the
metal to the Royal Society, stating that he had seen no mention of it in
any previous accounts of known minerals.
Brownrigg also made note of platinum's extremely high melting point and
refractoriness toward borax. Other
chemists across Europe soon began studying platinum, including Andreas
Sigismund Marggraf, Torbern Bergman, Jöns Jakob Berzelius, William Lewis, and Pierre
Macquer. In 1752, Henrik Scheffer published a detailed scientific description
of the metal, which he referred to as "white gold", including an
account of how he succeeded in fusing platinum ore with the aid of arsenic. Scheffer described platinum as being less
pliable than gold, but with similar resistance to corrosion.
No comments:
Post a Comment