Platinum
Its name is derived from the Spanish term platina, which is literally translated into "little silver". It is a dense, malleable, ductile, precious, gray-white transition metal.
Platinum has six naturally occurring isotopes. It is one of the rarest elements in the Earth's crust and has an average abundance of approximately 5 μg/kg. It is the least reactive metal. 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.
As a member of the platinum group of elements, as well as of the group 10 of the periodic table of elements, platinum is generally non-reactive. It exhibits a remarkable resistance to corrosion, even at high temperatures, and as such is considered a noble metal. As a result, 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 16th century, but it was not until Antonio de Ulloa published a report on a new metal of Colombian origin in 1748 that it became investigated by scientists.
Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewelry. Because only a few hundred tonnes are produced annually, it is a scarce material, and is highly valuable and is a major precious metal commodity. Being a heavy metal, it leads to health issues upon exposure to its salts, but due to its corrosion resistance, it is not as toxic as some metals. Compounds containing platinum, most notably cisplatin, are applied in chemotherapy against certain types of cancer.
Occurrence
Platinum is an extremely rare metal, occurring at a concentration of only 0.005 ppm in the Earth's crust. It is sometimes mistaken for silver (Ag). Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridium. Most often the native platinum is found in secondary deposits; platinum is combined with the other platinum group metals in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum group metals. Another large alluvial deposit is in the Ural Mountains, Russia, and it is still mined.
In nickel and copper deposits, platinum group metals occur as sulfides (e.g. (Pt,Pd)S), tellurides (e.g. PtBiTe), antimonides (PdSb), and arsenides (e.g. PtAs2), and as end alloys with nickel or copper. Platinum arsenide, sperrylite (PtAs2), is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. At Platinum, Alaska, about 545,000 troy ounces had been mined between 1927 and 1975. The mine ceased operations in 1990.[16] The rare sulfide mineral cooperite, (Pt,Pd,Ni)S, contains platinum along with palladium and nickel. Cooperite occurs in the Merensky Reef within the Bushveld complex, Gauteng, South Africa.
In 1865, chromites were identified in the Bushveld region of South Africa, followed by the discovery of platinum in 1906. The largest known primary reserves are in the Bushveld complex in South Africa. The large copper–nickel deposits near Norilsk in Russia, and the Sudbury Basin, Canada, are the two other large deposits. In the Sudbury Basin, the huge quantities of nickel ore processed make up for the fact platinum is present as only 0.5 ppm in the ore. Smaller reserves can be found in the United States, for example in the Absaroka Range in Montana. In 2010, South Africa was the top producer of platinum, with an almost 77% share, followed by Russia at 13%; world production in 2010 was 192,000 kg.
Platinum deposits are present in the state of Tamil Nadu, India. and a MOU has been signed between Geological Survey of India with TAMIN – Tamil Nadu Minerals Ltd.
Platinum exists in higher abundances on the Moon and in meteorites. Correspondingly, platinum is found in slightly higher abundances at sites of bolide impact on the Earth that are associated with resulting post-impact volcanism, and can be mined economically; the Sudbury Basin is one such example.
| Symbol | Pt | |
| Atomic Number | 78 | |
| Atomic Weight | 195.08 | |
| Oxidation States | +2,+4 | |
| Electronegativity, Pauling | 2.54 | |
| State at RT | solid | |
| Melting Point, K | 2045 | |
| Boiling Point, K | 4100 |
Appearance and Characteristics
Harmful effects:
Platinum is considered to be non-toxic.
Characteristics:
- Platinum is a precious metal; soft, silvery-white, and dense with a beautiful lustrous sheen.
- It is malleable and ductile and has a high melting point.
- Platinum does not oxidize in air even at high temperatures and is unaffected by common acids.
- It dissolves in aqua regia (mixture of nitric acid and hydrochloric acid in the ratio 1:3) forming chloroplatinic acid (H2PtCl6).
- It is also corroded by halogens, cyanides, sulfur, and caustic alkalis.
Uses of Platinum
- Platinum is widely used as a catalyst for chemical reactions. The most important use of platinum is in vehicles, as a catalytic converter, facilitating the complete combustion of unburned hydrocarbon passing through the exhaust.
- Platinum is used in jewelry, decoration and dental work. The metal and its alloys are also used for electrical contacts, fine resistance wires and medical / laboratory instruments.
- An alloy of platinum and cobalt is used to produce strong permanent magnets.
- The metal is also used to make electrodes sealed in glass (as its thermal coefficient of expansion is almost equal to that of glass).
Platinum acts as a catalyst for the decomposition of hydrogen peroxide into water and oxygen. Since platinum is acting as a catalyst, it is not consumed in the reaction.
Learn more about platinum’s history and properties.
