Platinum is a chemical element with the symbol Pt and atomic number 78. It is a transition metal that is dense, malleable, tough, highly unreacted, noble, silver-white. Its name comes from the Spanish term platinum , which means "little silver".
Platinum is a member of the platinum group element and group 10 of the periodic table of elements. It has six natural isotopes. This is one of the rare elements in the Earth's crust, with an average abundance of about 5 g/kg. This occurs in some nickel ore and copper along with some of the original deposits, mostly in South Africa, which accounts for 80% of world production. Because of its scarcity in the Earth's crust, only a few hundred tons are produced each year, and given its importance, it is valuable and is a major precious metal commodity.
Platinum is one of the least reactive metals. It has tremendous resistance to corrosion, even at high temperatures, and is therefore considered a precious metal. As a result, platinum is often found to be chemically unsuitable as the original platinum. Since it occurs naturally in alluvial sand from various rivers, it was first used by pre-Columbian South American natives to produce artifacts. It was referenced in European writings at the beginning of the 16th century, but it was not until Antonio de Ulloa published a report on a new metal from Colombia in 1748 that began to be investigated by scientists.
Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dental equipment, and jewelry. Being heavy metal, it leads to health problems after exposure to salt; but because of its resistance to corrosion, metallic platinum has not been associated with adverse health effects. Platinum-containing compounds, such as cisplatin, oxaliplatin and carboplatin, are applied in chemotherapy against certain types of cancer.
Video Platinum
Characteristics
Physical
Pure platinum is a shiny, ductile, and soft, silver-white metal. Platinum is more resilient than gold, silver or copper, making it the most ductile of pure metals, but softer than gold. The metal has excellent corrosion resistance, is stable at high temperatures and has stable electrical properties. Platinum is not oxidized, forming PtO 2 , at 500 Ã, Â ° C; This oxide can be easily removed thermally. It reacts vigorously with fluorine at 500 Â ° C (932 Â ° F) to form platinum tetrafluoride. It is also attacked by chlorine, bromine, iodine, and sulfur. Platinum is insoluble in hydrochloric and nitric acid, but soluble in hot water aqua regia (nitric acid hydrochloride), to form chloroplatinic acid, H 2 PtCl 6 .
Physical characteristics and chemical stability make it useful for industrial applications. Its resistance to wear and dull is perfect for use in fine jewelry.
Chemistry
The most common oxidation state of platinum is 2 and 4. The oxidation states 1 and 3 are less common, and are often stabilized by metal bonds in bimetallic (or polymetallic) species. As expected, tetracoordinate platinum (II) compounds tend to adopt 16-electron planar square geometry. Although the platinum element is generally unreacted, it dissolves in hot aqua regia to provide dilute chloroplatinic acid (H 2 PtCl 6 ):
- Pt 4 HNO 3 6 HCl -> H 2 PtCl 6 4 NO 2 4 H 2 O
As a soft acid, platinum has a high affinity for sulfur, as in dimethyl sulfoxide (DMSO); many DMSO complexes have been reported and care should be taken in the choice of reaction solvent.
In 2007, Gerhard Ertl won the Nobel Prize in Chemistry to determine the detailed molecular mechanism of the oxidation of carbon monoxide catalytic over platinum (catalytic converter).
Isotope
Platinum has six natural isotopes: 190 Pt, 192 Pt, 194 Pt, 195 Pt, 196 Pt, and 198 Pt. The most abundant of these is 195 Pt, consisting of 33.83% of all platinum. It is the only stable isotope with non-zero spins; with spin 1 / 2 , 195 Peak satellite Pt is often observed in 1 H and 31 P NMR spectroscopy (ie, Pt-phosphine and Pt-alkyl complexes). 190 Pt is the least amount of only 0.01%. Of the naturally occurring isotopes, only 190 Pt is unstable, although it decays with a half-life of 6.5 ÃÆ' - 10 11 Ã, year, causing a natural 15 Bq/kg of platinum activity. 198 Pt may experience alpha decay, but its decay is never observed (half-life is more than 3.2 ÃÆ' - 10 14 Ã, year); therefore, is considered stable. Platinum also has 31 synthetic isotopes starting in atomic mass from 166 to 202, making the total number of known isotopes 37. The most stable of these is 166 Pt, with a half-life of 300 Âμs, while the most stable is 193 Pt with a half-life of 50 years. Most of the decay of platinum isotopes by some combination of beta decay and alpha decay. 188 Pt, 191 Pt, and 193 Pt decay mainly by electron capture. 190 Pt and 198 Pt is predicted to have a very favorable double beta decay path. Genesis
Platinum is a very rare metal, occurring at a concentration of only 0.005 ppm in the Earth's crust. Sometimes mistaken for silver. Platinum is often found chemically as an indigenous platinum and as an alloy with other platinum-group metals and most iron. Most often the original platinum is found in secondary deposits in alluvial deposits. The alluvial deposits used by pre-Columbians in the ChocÃÆ'Â Departemen Department, Colombia are still a source for platinum group metals. Other large alluvial deposits exist in the Ural Mountains, Russia, and are still mined.
In nickel and copper deposits, platinum-group metals occur as sulphides (eg (Pt, Pd) S), telluride (eg PtBiTe), antimonides (PdSb), and arsenides (eg PtAs 2 ), and as a final alloy with nickel or copper. Platinum arsenide, sperrylite (PtAs 2 ), is the main source of platinum associated with nickel ore at the Sudbury Basin deposit in Ontario, Canada. In Alaska, about 17,000 kg (550,000 ozt) was mined between 1927 and 1975. The mine halted its operations in 1990. The rare mineral sulphide emblem, (Pt, Pd, Ni) S, contains platinum along with palladium and nickel. Cooperite takes place at Merensky Reef inside the Bushveld complex, Gauteng, South Africa.
In 1865, chromite was identified in the Bushveld region of South Africa, followed by the discovery of platinum in 1906. In 1924, geologist Hans Merensky discovered a large supply of platinum at the Bushveld Igneus Complex in South Africa. The specific layer he found, named Merensky Reef, contains about 75% of the known platinum in the world. Large nickel-copper deposits near Norilsk in Russia, and Sudbury Basin, Canada, are two other major deposits. In the Sudbury Basin, a large amount of nickel ore processed to form platinum facts is present only 0.5 ppm in ore. Smaller reserves can be found in the United States, for example in the Absaroka Range in Montana. In 2010, South Africa was a major producer of platinum, with a share of nearly 77%, followed by Russia at 13%; world production in 2010 was 192,000 kg (423,000 pounds).
Large platinum deposits are present in the state of Tamil Nadu, India.
Platinum exists in higher abundance in the Moon and in meteorites. Correspondingly, platinum is found in slightly higher abundance at sites of bolide influence on Earth associated with post-impact effects of volcanism, and can be economically mined; Sudbury Basin is one such example.
Maps Platinum
​​Compound
Halide
The hexachloroplatinic acid mentioned above may be the most important platinum compound, as it serves as a precursor for many other platinum compounds. By itself, it has various applications in photography, zinc etchings, indelible ink, coating, mirrors, porcelain dyes, and as a catalyst.
The treatment of hexachloroplatinic acid with ammonium salts, such as ammonium chloride, gives ammonium hexachloroplatinate, which is relatively insoluble in ammonium solution. This ammonium salt heating in the presence of hydrogen reduces it to platinum. Potassium hexachloroplatinate is also insoluble, and hexachloroplatinic acid has been used in the determination of potassium ions by gravimetry.
When hexachloroplatinic acid is heated, it decomposes via platinum (IV) chloride and platinum (II) chloride into platinum elements, although the reaction does not occur gradually:
- (H 3 O) 2 PtCl 6 Ã, Â · n H 2 O? P
2 HCl ( n 2) H 2 O - PtCl 4 ? PtCl 2 Cl 2
- PtCl 2 ? Pt Cl 2
All three reactions are reversible. Platinum (II) and platinum (IV) bromides are also known. Platinum hexafluoride is a powerful oxidizing agent capable of oxidizing oxygen.
Oxide
Platinum (IV) oxide, PtO 2 , also known as Adams' catalyst , is a black powder soluble in potassium hydroxide (KOH) and concentrated acid solution. PtO 2 and less common PTO both decompose during heating. Platinum (II, IV) oxide, Pt 3 O 4 , is formed in the following reaction:
- 2 Pt 2 Pt 4 4 O 2 - -> Pt 3 O 4
Other compounds
Unlike palladium acetate, platinum (II) acetate is not commercially available. If a base is desired, the halide has been used in conjunction with sodium acetate. The use of platinum (II) acetylacetonate has also been reported.
Several barium platinides have been synthesized in which platinum shows negative oxidation states ranging from -1 to -2. These include BaPt, Ba
3 Pt 2 , and Ba
2 Pt . Cesium platinide, Cs
2 Pt , a transparent crystal compound of red-dark has been shown to contain Pt 2 -
anions. Platinum also exhibits a negative oxidation state on electrochemically reduced surfaces. The negative oxidation status exhibited by platinum is unusual for metallic elements, and they are associated with relativistic stabilization of the 6s orbital.
Zeise salts, containing ethylene ligands, are among the first organometallic compounds to be found. Dichloro (cycloocta-1,5-diene) platinum (II) is a commercially available olefin complex, which contains a cod lig which is an abbreviation of 1,5-cyclooxadiene. The complex cod and halide are an easy starting point for platinum chemistry.
Cisplatin, or cis -diamminedichloroplatinum (II) is the first of a series of medicinal platinum (II) planar chemotherapy drugs.. Others include carboplatin and oxaliplatin. These compounds are capable of cross-linking DNA, and killing cells with similar pathways to alkylate chemotherapeutic agents. (Side effects of cisplatin include nausea and vomiting, hair loss, tinnitus, hearing loss, and nephrotoxicity.)
History
Initial use
Archaeologists have discovered traces of platinum in gold used in the burial of ancient Egypt as early as 1200 BC. However, the level of early knowledge of Egyptians about the metal is unclear. Very likely they do not recognize there is platinum in their gold.
The metal is used by pre-Columbian Americans near modern Esmeraldas, Ecuador to produce artifacts of white gold-platinum alloys. They use a relatively sophisticated powder metallurgy system. The platinum used in such objects is not a pure element, but a natural mixture of platinum group metals, with a small amount of palladium, rhodium, and iridium.
European Discovery
The first European reference to platinum appeared in 1557 in the writings of Italian humanist Julius Caesar Scaliger as a description of an unknown precious metal found between DariÃÆ' Â © n and Mexico, "which no Spanish fire or intelligence has not been able to melt". From their first encounter with platinum, the Spaniards generally see the metal as a sort of gold impurity, and are treated as such. It is often thrown away, and there is an official decree prohibiting the forgery of gold with platinum impurities.
In 1735, Antonio de Ulloa and Don Jorge Juan y Santacilia saw native American mining, while the Spaniards traveled through Colombia and Peru for eight years. Ulloa and Juan find mines with whitish metal nugget and take them home to Spain. Antonio de Ulloa returned to Spain and founded the first mineralogical laboratory in Spain and was the first laboratory to study systematically platinum, which in 1748. His historical account of the expedition included a description of platinum that can not be separated or calcined. Ulloa also anticipates 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 a superintend operation of mercury mining in Huancavelica.
In 1741, Charles Wood, a British metallurgist, uncovered various Colombian platinum samples in Jamaica, which he sent to William Brownrigg for further investigation.
In 1750, after studying platinum sent to him by Wood, Brownrigg presented a detailed account of metal to the Royal Society, stating that he never mentioned it in his previous account of known minerals. Brownrigg also noted the high melting point and refractoriness of platinum against borax. Other chemists in Europe soon began to study platinum, including Andreas Sigismund Marggraf, Torbern Bergman, JÃÆ'¶ns 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 explanation of how he successfully combined platinum ore with the aid of arsenic. Scheffer describes platinum as less flexible than gold, but with similar resistance to corrosion.
Means of flexibility
Carl von Sickingen examined platinum extensively in 1772. He succeeded in making platinum soft by mixing it with gold, dissolving the alloy in hot aqua regia, accelerating platinum with ammonium chloride, triggering ammonium chloroplatinate, and hammering the resulting platinum divided subtly to make it united. Franz Karl Achard created the first platinum container in 1784. He worked with platinum by combining it with arsenic, then vaporizing arsenic.
Since other platinum-family members have not been found (platinum is the first on the list), Scheffer and Sickingen made the false assumption that because of its hardness - a little more than for pure iron - platinum would be a relative non-pliable material, even brittle at times, when in fact ductility and elasticity are close to gold. Their assumptions are unavoidable because their platinum experiments are heavily contaminated with minute amounts of platinum-family elements such as osmium and iridium, inter alia, which encapsulate platinum alloys. The pure platinum residue alloy called "plyoxen" with gold is the only solution at the time to obtain the bending compound, but nowadays, very pure platinum is available and very long cables can be pulled from pure platinum, very easily, because the crystal structure, which is similar to many soft metals.
In 1786, Charles III of Spain provided libraries and laboratories for Pierre-FranÃÆ'§ois Chabaneau to assist in his research on platinum. Chabaneau managed to remove various impurities from the ore, including gold, mercury, lead, copper, and iron. This led him to believe that he was working with a single metal, but actually the ore still contained undiscovered platinum group metals. This results in inconsistent results in his experiment. Occasionally, platinum looks soft, but when mixed with iridium, it will be much more fragile. Sometimes the metal completely does not burn, but when mixed with osmium, it will evaporate. After several months, Chabaneau managed to produce 23 pounds of pure, soft platinum by hammering and compressing sponge forms while white-hot. Chabeneau realizes that platinum infusion will value the objects made of it, and start a business with JoaquÃÆ'n Cabezas producing ingots and platinum equipment. It started what is known as the "platinum age" in Spain.
Production
Platinum, together with platinum-group residual metals, is commercially obtained as a by-product of mining and nickel and copper processing. During electrorefining copper, precious metals such as silver, gold and platinum-group metals as well as selenium and tellurium settle into the bottom of the cell as "anode mud", which forms the starting point for the extraction of the platinum group of metals.
If pure platinum is found in placer deposits or other ores, it is isolated from them by various methods of decomposing the dirt. Because platinum is significantly denser than many of its impurities, the milder dirt can be removed by simply dissolving it in the liquid. Platinum is paramagnetic, while nickel and iron are both ferromagnetic. These two impurities are removed by running the electromagnet over the mixture. Because platinum has a higher melting point than most other substances, many impurities can be burned or melted without melting platinum. Finally, platinum is resistant to hydrochloric acid and sulfates, while other substances are vulnerable to them. Metal impurities can be removed by stirring the mixture in one of the two acids and restoring the remaining platinum.
One suitable method for purification for crude platinum, containing platinum, gold, and other platinum group metals, is to process it by aqua regia , in which palladium, gold and platinum are dissolved, while osmium, iridium , ruthenium and rhodium remain unreacted. Gold is precipitated by the addition of iron (II) chloride and after filtering the gold, platinum is precipitated as ammonium chloroplatinate with the addition of ammonium chloride. Ammonium chloroplatinate can be converted to platinum by heating. Unpredicted Hexachloroplatinate (IV) may be reduced by elemental zinc, and similar methods are suitable for platinum small recovery from the laboratory residue. Mine and refining platinum have an environmental impact.
Apps
Of the 218 ton platinum sold in 2014, 98 tonnes were used for vehicle emissions control equipment (45%), 74.7 tonnes for jewelry (34%), 20.0 tonnes for chemical production and oil refining (9.2%) , and 5.85 Ã, tons for electrical applications such as hard disk drives (2.7%). The remaining 28.9 tons went to various other small applications, such as drugs and biomedicine, glassmaking equipment, investments, electrodes, anticancer drugs, oxygen sensors, spark plugs and turbine engines.
Catalyst
The most common use of platinum is as a catalyst in chemical reactions, often as black platinum. It has been used as a catalyst since the beginning of the 19th century, when platinum powder was used to catalyze hydrogen ignition. The most important application is in the car as a catalytic converter, which allows complete combustion of low concentrations of unburned hydrocarbons from exhaust to carbon dioxide and water vapor. Platinum is also used in the petroleum industry as a catalyst in a number of separate processes, but especially in the catalytic reform of straight-run naphthas into high-octane gasoline that becomes rich in aromatic compounds. PtO 2 , also known as Adams catalyst, is used as a hydrogenation catalyst, especially for vegetable oils. Platinum also highly catalyzes the decomposition of hydrogen peroxide into water and oxygen and is used in fuel cells as a catalyst for oxygen reduction.
Standard
From 1889 to 1960, the meter was defined as the length of the platinum-iridium (90:10) alloy bar, known as the International Prototype Meter bar. The previous bar was made of platinum in 1799. The International Kilogram Prototype was still defined by a cylinder of the same platinum-iridium alloy created in 1879.
Standard hydrogen electrodes also use platinum platinum electrodes due to their corrosion resistance, and other attributes.
As an investment
Platinum is a precious metal commodity; the bars have an ISO currency code of ISO. Coins, bars, and bars are traded or collected. Platinum finds use in jewelry, usually as a 90-95% alloy, because of its slowness. This is used for this purpose for the prestige and the value of the inherent stone. Jewelry trading publications suggest jewelry to present minute surface scratches (which they call patina) as a desirable feature in an effort to increase the value of platinum products.
In watchmaking, Vacheron Constantin, Patek Philippe, Rolex, Breitling, and other companies use platinum to produce their limited edition watch series. Clock makers appreciate the unique properties of platinum, because it does not smear or wear (the last quality relative to gold).
Platinum prices, like other industrial commodities, are more unstable than gold. In 2008, the price of platinum fell from $ 2,252 to $ 774 per oz, a loss of almost 2/3 of its value. In contrast, the price of gold fell from ~ $ 1,000 to ~ $ 700/oz over the same timeframe, losing only 1/3 of its value.
During periods of stability and sustained economic growth, platinum prices tended to double the price of gold, while during periods of economic uncertainty, platinum prices tended to decline due to reduced industrial demand, falling below the price of gold. Gold prices are more stable in times of slow economy, because gold is considered a safe place. Although gold is used in industrial applications, its demand is not so driven by industrial use. In the 18th century, the scarcity of platinum made King Louis XV of France declare it the only metal suitable for a king.
Other uses
In the laboratory, platinum wire is used for electrodes; platinum and supporting pans are used in thermogravimetry analysis due to the strict requirements of chemical inertia when heating to high temperatures (~ 1000Ã, Â ° C). Platinum is used as an alloying agent for a variety of metal products, including fine wire, non-corrosive laboratory containers, medical equipment, dental prostheses, electrical contacts, and thermocouples. Platinum-cobalt, an alloy of about three parts platinum and one part cobalt, is used to create a relatively strong permanent magnet. Platinum-based anodes are used in ships, pipes, and steel docks.
Prestige symbol in marketing
The scarcity of Platinum as a metal causes advertisers to associate it with exclusivity and wealth. Debit and credit cards "Platinum" have greater privileges than "gold" cards. The "Platinum Award" is the second highest, ranking above "gold", "silver" and "bronze", but below the diamond. For example, in the United States, a music album that has sold over 1 million copies will be credited as "platinum", while an album that has sold over 10 million copies will be certified as a "diamond". Some products, such as blenders and vehicles, in silvery white are identified as "platinum". Platinum is considered a precious metal, although its use is not as common as the use of gold or silver. The Crown Queen Queen Elizabeth's Empress, made for her coronation as Empress of King George VI, is made of platinum. It was the first British crown made of this particular metal.
Health issues
According to the Centers for Disease Control and Prevention, short-term exposure to platinum salts may cause irritation of the eyes, nose, and throat, and long-term exposure may cause respiratory and skin allergies. The current OSHA standard is 2 micrograms per cubic meter of air that is averaged over 8 hours of work shift. The National Institute for Occupational Safety and Health has set a recommended exposure limit (REL) for platinum as 1 mg/m 3 for 8 hours of work.
Platinum-based antineoplastic agents are used in chemotherapy, and show good activity against some tumors.
Because platinum is a catalyst in the manufacture of rubber components and silicone gel of some types of medical implants (breast implants, joint prosthetics, artificial lumbar discs, vascular access, etc.), the possibility that platinum may enter the body and cause adverse effects feasible. The Food and Drug Administration and other institutions have reviewed this issue and found no evidence to suggest in vivo toxicity.
See also
- List of countries by platinum production
- Mixed metal oxide electrodes
- Platinum in Africa
- Platinum nanoparticles
- Iron-platinum nanoparticles
- Print platinum
- commodity boom of the 2000s
- Platinum Group
References
Further reading
-
Young, Gordon (November 1983). "The Miracle Metal - Platinum". National Geographic . Vol.Ã, 164 no.Ã, 5. pp.Ã, 686-706. ISSNÃ, 0027-9358. OCLCÃ, 643483454.
External links
- Platinum in the Periodic Video Table (University of Nottingham)
- Nuclear and Isotopes Fourth Edition: Nuclide Chart, General Electric Company, 1989.
- NIOSH A Pocket Guide for Chemical Hazards - Platinum Center for Disease Control and Prevention
- "The PGM Database".
- "A balanced historical account of the sequence of platinum discovery, illustrated".
- "Johnson Matthey Technology Review: A free quarterly research journal exploring science and technology in industrial applications (previously published as Metal Metals Review)".
- "Platinum Metals and Information Statistics". United States Geological Survey.
Source of the article : Wikipedia
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