Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metalin group 7 of the periodic table. With an average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. Sony VAIO VGN-CR11H/B Battery
The free element has the third-highestmelting point and highest boiling point of any element. Rhenium resembles manganese chemically and is obtained as a by-product of molybdenum and copper refinement. Rhenium shows in its compounds a wide variety of oxidation states ranging from ?1 to +7. Sony VAIO VGN-CR11S/L Battery
Discovered in 1925, rhenium was the last stable element to be discovered. It was named after the river Rhine in Europe.
Nickel-based superalloys for use in jet engines contain up to 6% rhenium, making jet engine construction the largest use for the element, with chemical industry catalytic uses being next-most important. Sony VAIO VGN-CR11H/B Battery
Because of the low availability relative to demand, rhenium is among the most expensive industrial metals, with an average price of approximately US$4,575 perkilogram, on 1 August 2011.[1]
Rhenium (Latin: Rhenus meaning: "Rhine")[2] was the last element to be discovered having a stable isotope (other new radioactive elements have been discovered in nature since then, such as neptunium and plutonium). Sony VAIO VGN-CR11S/L Battery
The existence of a yet undiscovered element at this position in the periodic table had been first predicted by Dmitry Mendeleev. Other calculated information was obtained by Henry Moseley in 1914.[4] It is generally considered to have been discovered byWalter Noddack, Ida Tacke, and Otto Berg in Germany. Sony VAIO VGN-CR11S/P Battery
In 1925 they reported that they detected the element in platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite.[5] In 1928 they were able to extract 1 g of the element by processing 660 kg of molybdenite.[6] The process was so complicated and expensive that production was discontinued until early 1950 when tungsten-rhenium and molybdenum-rhenium alloys were prepared. Sony VAIO VGN-CR11S/W Battery
These alloys found important applications in industry that resulted in a great demand for the rhenium produced from the molybdenite fraction of porphyry copper ores.
In 1908, Japanese chemist Masataka Ogawa announced that he discovered the 43rd element and named it nipponium (Np) afterJapan (which is Nippon in Japanese). Sony VAIO VGN-CR11Z/R Battery
However, later analysis indicated the presence of rhenium (element 75), not element 43.[7] The symbol Np was later used for the element neptunium.
Characteristics
Rhenium is a silvery-white metal with one of the highest melting points of all elements, exceeded by only tungsten andcarbon. It is also one of the densest, exceeded only by platinum, iridium and osmium. Sony VAIO VGN-CR120E/L Battery
Sony VAIO VGN-CR120E/P Battery
Its usual commercial form is a powder, but this element can be consolidated by pressing and sintering in a vacuum orhydrogenatmosphere. This procedure yields a compact solid having a density above 90% of the density of the metal. Sony VAIO VGN-CR120E/R Battery
Whenannealed this metal is very ductile and can be bent, coiled, or rolled.[8] Rhenium-molybdenum alloys are superconductiveat 10 K; tungsten-rhenium alloys are also superconductive[9] around 4-8 K, depending on the alloy. Rhenium metal superconducts at 2.4 K.[10][11] Sony VAIO VGN-CR120E/W Battery
Rhenium has a stable isotope, rhenium-185, which nevertheless occurs in minority abundance, a situation found only in one other element (indium). Naturally occurring rhenium is 37.4% 185Re, which is stable, and 62.6% 187Re, which is unstablebut has a very long half-life (~1010 years). Sony VAIO VGN-CR125E/B Battery
This lifetime is affected by the charge state of rhenium atom.[12][13] Thebeta decay of 187Re is used for rhenium-osmium dating of ores. The available energy for this beta decay (2.6 keV) is one of the lowest known among all radionuclides. There are twenty-six other recognized radioactive isotopes of rhenium.[14] Sony VAIO VGN-CR13/B Battery
Compounds
Rhenium has nine known oxidation states: ?1, 0, +1, +2, +3, +4, +5, +6 and +7.[15] The oxidation states +7, +6, +4, and +2 are the most common.[15] Sony VAIO VGN-CR13/L Battery
The most common rhenium compounds are the oxides and the halides exhibiting a broad oxidation number spectrum: Re2O7, ReO3, Re2O5, ReO2, and Re2O3 are the known oxides, and ReF7, ReCl6, ReCl5, ReCl4 and ReCl3 are a few of the known halogen derivatives.[16] Known sulfides are ReS2 and Re2S7.[16] Sony VAIO VGN-CR13/P Battery
Reaction of rhenium with hydrogen produces the negatively charged hydride [ReH9]2? ion, which is isostructural with [TcH9]2?. It consists of a trigonal prism with Re atom in the center and six hydrogen atoms at the corners. Sony VAIO VGN-CR13/R Battery
Three more hydrogens make a triangle lying parallel to the base and crossing the prism in its center (see figure). Although those hydrogen atoms are not equivalent geometrically, their electronic structure is almost the same. The coordination number 9 in this complex is the highest for a rhenium complex. Sony VAIO VGN-CR13/W Battery
Sony VAIO VGN-CR131E/L Battery
Two protons in it can be replaced by sodium (Na+) or potassium (K+) ions.[17]
Rhenium is most available commercially as the sodium and ammonium perrhenates. It is also readily available as dirhenium decacarbonyl; these three compounds are common entry points to rhenium chemistry. Sony VAIO VGN-CR13G Battery
Various perrhenate salts may be easily converted to tetrathioperrhenate by the action of ammonium hydrosulfide.[18] It is possible to reduce the dirhenium decacarbonylRe2(CO)10 by reacting it with sodium amalgam to Na[Re(CO)5] with rhenium in the formal oxidation state ?1.[19Sony VAIO VGN-CR13G/B Battery
]Dirhenium decacarbonyl may be oxidatively cleaved with bromine to givebromopentacarbonylrhenium(I),[20] then reduced with zincand acetic acid topentacarbonylhydridorhenium:[21] Sony VAIO VGN-CR13G/L Battery
Re2(CO)10 + Br2 ? 2 Re(CO)5Br
Re(CO)5Br + Zn + HOAc ? Re(CO)5H + ZnBr(OAc)
Bromopentacarbonylrhenium(I) may be decarbonylated to give the rhenium tricarbonyl fragment either by refluxing in water:[22] Sony VAIO VGN-CR13G/P Battery
Re(CO)5Br + 3 H2O ? [Re(CO)3(H2O)3]Br + 2 CO
or by reacting with tetraethylammonium bromide:[23]
Re(CO)5Br + 2 NEt4Br ? [NEt4]2[Re(CO)3Br3] + 2 CO
Rhenium diboride (ReB2) is a hard compound having the hardness similar to that of tungsten carbide, silicon carbide, titanium diboride or zirconium diboride.[24] Sony VAIO VGN-CR13G/R Battery
Rhenium was originally thought to form the rhenide anion, Re?
, in which it has the ?1 oxidation state. This was based on the product of the reduction of perrhenatesalts, such as the reduction of potassium perrhenate (KReO4) by potassium metal.[25] "Sony VAIO VGN-CR13G/W Battery
Potassium rhenide" was shown to exist as a tetrahydrated complex, with the postulated chemical formula KRe·4H2O.[26] This compound exhibits strongly reducing properties, and slowly yields hydrogen gas when dissolved in water. The lithium and thallous salts were also reported. Sony VAIO VGN-CR13T/L Battery
Later rese
"Potassium rhenide" was shown to be in fact the nonahydridorhenate, K2ReH9, containing the ReH92? anion in which the oxidation state of rhenium is actually +7.[27][28] Other methods of reduction of perrhenate salts yield compounds containing other hydrido- complexes, including ReH3(OH)3(H2O)?. arch, however, indicates that the "rhenide" ion is actually a hydridorhenate complex. Sony VAIO VGN-CR13T/P Battery
Occurrence
Rhenium is one of the rarest elements in Earth's crust with an average concentration of 1 ppb;[16] other sources quote the number of 0.5 ppb making it the 77th most abundant element in Earth's crust.[30] Rhenium is probably not found free in nature (its possible natural occurrence is uncertain), but occurs in amounts up to 0.2%[1Sony VAIO VGN-CR13T/R Battery
6] in the mineral molybdenite (which is primarily molybdenum disulfide), the major commercial source, although single molybdenite samples with up to 1.88% have been found.[31]Chile has the world's largest rhenium reserves, part of the copper ore deposits, and was the leading producer as of 2005.[32] Sony VAIO VGN-CR13T/W Battery
It was only recently that the first rhenium mineral was found and described (in 1994), a rhenium sulfide mineral (ReS2) condensing from a fumaroleon Russia's Kudriavy volcano, Iturup island, in the Kurile Islands.[33] Kudryavy discharges up to 20–60 kg rhenium per year mostly in the form of rhenium disulfide. Sony VAIO VGN-CR15/B Battery
Named rheniite, this rare mineral commands high prices among collectors.[36]
Production
Commercial rhenium is extracted from molybdenum roaster-flue gas obtained from copper-sulfide ores. Some molybdenum ores contain 0.001% to 0.2% rhenium.[ Sony VAIO VGN-CR150E/B Battery
Rhenium(VII) oxide and perrhenic acid readily dissolve in water; they are leached from flue dusts and gasses and extracted by precipitating with potassium or ammonium chloride as the perrhenate salts, and purified byrecrystallization.[37] Total world production is between 40 and 50 tons/year; the main producers are in Chile, the United States, Peru, and Kazakhstan.[38] Sony VAIO VGN-CR190 Battery
Recycling of used Pt-Re catalyst and special alloys allow the recovery of another 10 tons per year. Prices for the metal rose rapidly in early 2008, from $1000–$2000 per kg in 2003-2006 to over $10,000 in February 2008.[39][40]The metal form is prepared by reducing ammonium perrhenate with hydrogen at high temperatures:[37] Sony VAIO VGN-CR190E/L Battery
2 NH4ReO4 + 7 H2 ? 2 Re + 8 H2O + 2 NH3
Applications
The F-15 engine uses rhenium-containing second-generation superalloys
Rhenium is added to high-temperature superalloys that are used to make jet engine parts, making 70% of the worldwide rhenium production.[41] Sony VAIO VGN-CR190E/P Battery
Another major application is in platinum-rhenium catalysts, which are primarily used in making lead-free, high-octane gasoline.[42]
Alloys
The nickel-based superalloys have improved creep strength with the addition of rhenium. The alloys normally contain 3% or 6% of rhenium.[43] Sony VAIO VGN-CR190E/R Battery
Second generation alloys contain 3%; these alloys were used in the engines of the F-16 and F-15, while the newer single-crystal third generation alloys contain 6% of rhenium; they are used in the F-22 and F-35 engines.[42][44] Rhenium is also used in the superalloys, such as CMSX-4 (2nd gen) and CMSX-10 (3rd gen) that are used in industrial gas turbine engines like the GE 7FA. Sony VAIO VGN-CR190E/W Battery
Rhenium can cause superalloys to become microstructurally unstable, forming undesirable TCP (topologically close packed)phases. In 4th and 5th generation superalloys, ruthenium is used to avoid this effect. Among others the new superalloys are EPM-102 (with 3 % Ru) and TMS-162 (with 6 % Ru), both containing 6 % rhenium,[45] as well as TMS-138[46] and TMS-174.[47][48] Sony VAIO VGN-CR19VN/B Battery
For 2006, the consumption is given as 28% for General Electric, 28% Rolls-Royce plc and 12% Pratt & Whitney, all for superalloys, while the use for catalysts only accounts for 14% and the remaining applications use 18%.[41] In 2006, 77% of the rhenium consumption in the United States was in alloys.[42] Sony VAIO VGN-CR19XN/B Battery
The rising demand for military jet engines and the constant supply made it necessary to develop superalloys with a lower rhenium content. For example the newer CFM International CFM56 high-pressure turbine (HPT) blades will use Rene N515 with a rhenium content of 1.5 % instead of Rene N5 with 3 %.[49][50] Sony VAIO VGN-CR20 Battery
Rhenium improves the properties of tungsten and is therefore the most important alloying material for tungsten. Tungsten-rhenium alloys are more ductile at low temperature making them easier to machine, while the high-temperature stability is also improved. Sony VAIO VGN-CR21/B Battery
The effect increases with the rhenium concentration, and therefore tungsten alloys are produced with up to 27% of Re, which is the solubility limit.[51] One application for the tungsten-rhenium alloys is X-ray sources. The high melting point of both compounds, together with the high atomic mass, makes them stable against the prolonged electron impact.[52] Sony VAIO VGN-CR21E/L Battery
Rhenium tungsten alloys are also applied as thermocouples to measure temperatures up to 2200 °C.[53]
The high temperature stability, low vapor pressure, good wear resistance and ability to withstand arc corrosion of rhenium are useful in self-cleaning electrical contacts. In particular, the discharge occurring during the switching oxidizes the contacts. Sony VAIO VGN-CR21E/P Battery
However, rhenium oxide Re2O7 has poor stability (sublimates at ~360 °C) and therefore is removed during the discharge.[41]
Rhenium has a high melting point and a low vapor pressure similar to tantalum and tungsten, however, rhenium forms no volatile oxides. Sony VAIO VGN-CR21E/W Battery
Therefore, rhenium filaments exhibit a higher stability if the filament is operated not in vacuum, but in oxygen-containing atmosphere.[54] Those filaments are widely used in mass spectrometers, in ion gauges.[55] and in photoflash lamps in photography.[56] Sony VAIO VGN-CR21S/L Battery
Catalysts
Rhenium in the form of rhenium-platinum alloy is used as catalyst for catalytic reforming, which is a chemical process to convert petroleum refinery naphthas with low octane ratings into high-octane liquid products. Sony VAIO VGN-CR21S/P Battery
Worldwide, 30% of catalysts used for this process contain rhenium.[57] The olefin metathesis is the other reaction for which rhenium is used as catalyst. Normally Re2O7on alumina is used for this process.[58] Rhenium catalysts are very resistant to chemical poisoningfrom nitrogen, sulfur and phosphorus, and so are used in certain kinds of hydrogenation reactions. Sony VAIO VGN-CR21S/W Battery
Other uses
188Re and 186Re isotopes are radioactive and are used for treatment of liver cancer. They both have similar penetration depth in tissue (5 mm for 186Re and 11 mm for188Re), but 186Re has advantage of longer lifetime (90 hours vs. 17 hours). Sony VAIO VGN-CR21Z/N Battery
Related by periodic trends, rhenium has a similar chemistry with technetium; work done to label rhenium onto target compounds can often be translated to technetium. This is useful for radiopharmacy, where it is difficult to work with technetium – especially the 99m isotope used in medicine – due to its expense and short half-life. Sony VAIO VGN-CR21Z/R Battery
Precaution
Very little is known about the toxicity of rhenium and its compounds because they are used in very small amounts. Soluble salts, such as the rhenium halides or perrhenates, could be hazardous due to elements other than rhenium or due to rhenium itself.[ Sony VAIO VGN-CR220E/R Battery
Only a few compounds of rhenium have been tested for their acute toxicity; two examples are potassium perrhenate and rhenium trichloride, which were injected as a solution into rats. The perrhenate had an LD50 value of 2800 mg/kg after seven days (this is very low toxicity, similar to that of table salt) and the rhenium trichloride showed LD50 of 280 mg/kg. Sony VAIO VGN-CR23/B Battery
Sony VAIO VGN-CR23/L Battery
Osmium is a chemical element with the symbol Os and atomic number 76. Osmium is a hard, brittle, blue-gray or blue-black transition metal in the platinum family, and is the densest natural element. Osmium is twice as dense as lead. Sony VAIO VGN-CR23/N Battery
The density of osmium is 22.59 g/cm3, slightly greater than that of iridium, the second densest element. Osmium is found in nature as an alloy, mostly in platinum ores. Osmium is also used in alloys, with platinum, iridium and other platinum group metals. Those alloys are employed in fountain pen tips, electrical contacts and in other applications where extreme durability and hardness are needed.[2] Sony VAIO VGN-CR23/P Battery
Physical properties
Osmium has a blue-gray tint and is the densest stable element, slightly denser thaniridium.[3] Calculations of density from the X-ray diffraction data may produce the most reliable data for these elements, giving a value of 22.562±0.009 g/cm3 for iridium versus 22.587±0.009 g/cm3 for osmium.[4] The high density of osmium is a consequence of the lanthanide contraction.[4][5] Sony VAIO VGN-CR23/R Battery
Osmium is a hard but brittle metal that remains lustrous even at high temperatures. It has a very low compressibility. Correspondingly, its bulk modulus is extremely high, reported between 395 and 462 GPa, which rivals that of diamond (443 GPa). Sony VAIO VGN-CR23/W Battery
The hardness of osmium is moderately high at 4 GPa.[6][7][8] Because of its hardness, brittleness, low vapor pressure (the lowest of the platinum group metals), and very high melting point (the fourth highest of all elements), solid osmium is difficult to machine, form or work. Sony VAIO VGN-CR240E/B Battery
Chemical properties
Osmium forms compounds with the oxidation states ranging from ?2 to +8. The most common oxidation states are +2, +3, +4, and +8. The +8 oxidation state is notable for being the highest attained by any chemical element, and aside from osmium, is encountered only inxenon, iron [9] and ruthenium.[10] Sony VAIO VGN-CR240N/B Battery
The oxidation state ?1 and ?2 represented by the two reactive compounds Na2[Os4(CO)13] and Na2[Os(CO)4] are used in the synthesis of osmiumcluster compounds.[11][12]
The most common compound exhibiting the +8 oxidation state is osmium tetroxide. Sony VAIO VGN-CR25G/N Battery
This toxic compound is formed when powdered osmium is exposed to air, and is a very volatile, water-soluble, pale yellow, crystalline solid with a strong smell. Therefore, osmium powder has a characteristic smell of osmium tetroxide.[13] Osmium tetroxide forms red osmates OsO4(OH)2?
2 upon reaction with a base. Sony VAIO VGN-CR290EAL Battery
With ammonia, it forms the nitrido-osmatesOsO3N?.[14][15][16] Osmium tetroxide boils at 130 °C and is a powerful oxidizing agent. By contrast, osmium dioxide (OsO2) is black, non-volatile, and much less reactive and toxic.
Only two osmium compounds have major applications: osmium tetroxide — for stainingtissue in electron microscopy and the non-volatile osmates for organic oxidation reactions.[17] Sony VAIO VGN-CR290EAN Battery
Osmium heptafluoride (OsF7) and osmium pentafluoride (OsF5) are known, but osmium trifluoride (OsF3) has not been synthesized yet. The lower oxidation states are stabilized by the larger halogens. Therefore, the trichloride, tribromide, triiodide and even osmium diiodide are known. Sony VAIO VGN-CR290EAP Battery
The oxidation state +1 is only known for the osmium iodide (OsI), whereas several carbonyl complexes of osmium, such as triosmium dodecacarbonyl (Os3(CO)12), represent the oxidation state 0.[14][15][18][19]
In general, the lower oxidation states of osmium are stabilized by ligands that are good ?-donors (such as amines) and ?-acceptors (heterocycles containing nitrogen).
The higher oxidation states are stabilized by strong ?- and ?-donors, such as O2? and N3?.[20]
Osmium has seven naturally occurring isotopes, six of which are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. Sony VAIO VGN-CR290EAR Battery
186Os undergoes alpha decay with such long half-life ((2.0±1.1)×1015 years) that for practical purposes it can be considered stable. Alpha decay is predicted for all 7 naturally occurring isotopes, but due to very long half-lives, it was observed only for 186Os. It is predicted that 184Os and 192Os can undergo double beta decay but this radioactivity has not been observed yet.[21] Sony VAIO VGN-CR290EAW Battery
187Os is the daughter of 187Re (half-life 4.56×1010 yr) and is used extensively in dating terrestrial as well as meteoricrocks(see rhenium-osmium dating). It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. Sony VAIO VGN-CR29XN/B Battery
This decay is a reason why rhenium-rich minerals are abnormally rich in 187Os.[22] However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the K-T boundary that marks the extinction of thedinosaurs 65 million years ago.[23] Sony VAIO VGN-CR305E/RC Battery
Osmium (from Greek osme (????) meaning "smell") was discovered in 1803 by Smithson Tennant and William Hyde WollastoninLondon, England.[24] The discovery of osmium is intertwined with that of platinum and the other metals of the platinum group. Platinum reached Europe as platina ("small silver"), first encountered in the late 17th century in silver mines around the Chocó Department, in Colombia.[25] Sony VAIO VGN-CR31S/D Battery
The discovery that this metal was not an alloy, but a distinct new element, was published in 1748.[26]Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids) to create soluble salts. They always observed a small amount of a dark, insoluble residue.[27] Sony VAIO VGN-CR323/W Battery
Joseph Louis Proustthought that the residue was graphite.[27]Victor Collet-Descotils, Antoine François, comte de Fourcroy, and Louis Nicolas Vauquelin also observed the black residue in 1803, but did not obtain enough material for further experiments.[27]
In 1803, Smithson Tennant analyzed the insoluble residue and concluded that it must contain a new metal. Sony VAIO VGN-CR33 Battery
Vauquelin treated the powder alternately with alkali and acids[28] and obtained a volatile new oxide, which he believed to be of this new metal—which he named ptene, from the Greek word ?????? (ptènos) for winged.[29][30] However, Tennant, who had the advantage of a much larger amount of residue, continued his research and identified two previously undiscovered elements in the black residue, iridium and osmium.[27][28] Sony VAIO VGN-CR382 Battery
He obtained a yellow solution (probably of cis–[Os(OH)2O4]2?) by reactions with sodium hydroxide at red heat. After acidification he was able to distill the formed OsO4.[29] He named osmium after Greek osme meaning "a smell", because of the ashen and smoky smell of the volatile osmium tetroxide.[31]Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.[27][32] Sony VAIO VGN-CR490EBL Battery
Uranium and osmium were early successful catalysts in the Haber process, the nitrogen fixation reaction of nitrogen andhydrogen to produce ammonia, giving enough yield to make the process economically successful. However, in 1908 cheaper catalysts based on iron and iron oxides were introduced for the first pilot plants.[33] Sony VAIO VGN-CR490EBN Battery
Nowadays, osmium is primarily obtained from the processing of platinum and nickel ores.[34]
Occurrence
Osmium is the least abundant stable element in the Earth's crust with an average mass fraction of 0.05 ppb in thecontinental crust.[35] Sony VAIO VGN-CR490EBP Battery
Osmium is found in nature as an uncombined element or in natural alloys; especially the iridium–osmium alloys, osmiridium(osmium rich), and iridiosmium (iridium rich).[28] In the nickel and copper deposits, the platinum group metals occur as sulfides(i.e., (Pt,Pd)S)), tellurides (e.g., PtBiTe), antimonides (e.g., PdSb), and arsenides (e.g., PtAs2); Sony VAIO VGN-CR490EBR Battery
in all these compounds platinum is exchanged by a small amount of iridium and osmium. As with all of the platinum group metals, osmium can be found naturally in alloys with nickel or copper.[36]
Within the Earth's crust, osmium, like iridium, is found at highest concentrations in three types of geologic structure: Sony VAIO VGN-CR490EBT Battery
igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one of the former structures. The largest known primary reserves are in the Bushveld igneous complex in South Africa,[37] though the large copper–nickel deposits nearNorilsk in Russia, and the Sudbury Basin in Canada are also significant sources of osmium. Sony VAIO VGN-CR490EBW Battery
Smaller reserves can be found in the United States.[37] The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum group metals. The second large alluvial deposit was found in the Ural Mountains, Russia, which is still mined.[34][38] Sony VAIO VGN-CR50B/W Battery
Production
Osmium is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copperand nickel, noble metals such as silver, gold and the platinum group metals, together with non-metallic elements such as seleniumand tellurium settle to the bottom of the cell as anode mud, which forms the starting material for their extraction. Sony VAIO VGN-CR51B/W Battery
In order to separate the metals, they must first be brought into solution. Several methods are available depending on the separation process and the composition of the mixture; two representative methods are fusion with sodium peroxide followed by dissolution inaqua regia, and dissolution in a mixture of chlorine with hydrochloric acid.[37][41] Sony VAIO VGN-CR520E/J Battery
Osmium, ruthenium, rhodium and iridium can be separated from platinum, gold and base metals by their insolubility in aqua regia, leaving a solid residue. Rhodium can be separated from the residue by treatment with molten sodium bisulfate. The insoluble residue, containing Ru, Os and Ir, is treated with sodium oxide, in which Ir is insoluble, producing water-soluble Ru and Os salts. Sony VAIO VGN-CR52B/W Battery
After oxidation to the volatile oxides,RuO4 is separated from OsO4 by precipitation of (NH4)3RuCl6 with ammonium chloride.
After it is dissolved, osmium is separated from the other platinum group metals by distillation or extraction with organic solvents of the volatile osmium tetroxide.[42] Sony VAIO VGN-CR590EBL Battery
The first method is similar to the procedure used by Tennant and Wollaston. Both methods are suitable for industrial scale production. In either case, the product is reduced using hydrogen, yielding the metal as a powder or sponge that can be treated using powder metallurgy techniques.[43] Sony VAIO VGN-CR590EBN Battery
Neither the producers nor the United States Geological Survey published any production amounts for osmium. Estimations of the United States consumption date published from 1971,[44] which gives a consumption in the United States of 2000 troy ounces(62 kg), would suggest that the production is still less than 1 ton per year. Sony VAIO VGN-CR590EBP Battery
Applications
Because of the volatility and extreme toxicity of its oxide, osmium is rarely used in its pure state, and is instead often alloyed with other metals. Those alloys are utilized in high-wear applications. Sony VAIO VGN-CR590EBR Battery
Osmium alloys such as osmiridium are very hard and, along with other platinum group metals, are used in the tips of fountain pens, instrument pivots, and electrical contacts, as they can resist wear from frequent operation. The stylus (needle) in early phonograph designs was also made of osmium, especially for 78-rpm records, until sapphire and synthetic diamond replaced the metal in later designs for 45-rpm and 33-rpmlong-playing records.[45] Sony VAIO VGN-CR590EBT Battery
Osmium tetroxide has been used in fingerprint detection[46] and in staining fattytissue for optical and electron microscopy. As a strong oxidant, it cross-links lipids mainly by reacting with unsaturated carbon-carbon bonds, and thereby both fixes biological membranes in place in tissue samples and simultaneously stains them. Sony VAIO VGN-CR590EBW Battery
Because osmium atoms are extremely electron dense, osmium staining greatly enhances image contrast in transmission electron microscopy (TEM) studies of biological materials. Those carbon materials have otherwise very weak TEM contrast (see image).[17] Another osmium compound, osmium ferricyanide (OsFeCN), exhibits similar fixing and staining action.[47] Sony VAIO VGN-CR60B/L Battery
An alloy of 90% platinum and 10% osmium is used in surgical implants such as pacemakers and replacement of pulmonaryvalves.[48]
The tetroxide and a related compound, potassium osmate, are important oxidants for chemical synthesis, despite being very poisonous. Sony VAIO VGN-CR60B/P Battery
For the Sharpless asymmetric dihydroxylation, which uses osmate for the conversion of a double bond into a vicinaldiol, Karl Barry Sharpless won the Nobel Prize in Chemistry in 2001.[49][50]
In 1898 an Austrian chemist, Auer von Welsbach, developed the Oslamp with a filament made of osmium, which he introduced commercially in 1902. Sony VAIO VGN-CR60B/R Battery
After only a few years, osmium was replaced by the more stable metal tungsten (also known as wolfram). Tungsten has the highest melting point of any metal, and using it in light bulbs increases the luminous efficacy and life of incandescent lamps.[29] Sony VAIO VGN-CR61B/L Battery
The light bulb manufacturer OSRAM (founded in 1906 when three German companies, Auer-Gesellschaft, AEG and Siemens & Halske, combined their lamp production facilities) derived its name from the elements of OSmium and wolfRAM.[53]
Like palladium, powdered osmium effectively absorbs hydrogen atoms. Sony VAIO VGN-CR61B/N Battery
This could make osmium a potential candidate for a metal hydride battery electrode. However, osmium is expensive and would react with potassium hydroxide, the most common battery electrolyte.[54]
Osmium has high reflectivity in the ultraviolet range of the electromagnetic spectrum; for example, at 600 Å osmium has a reflectivity twice that of gold.[55] Sony VAIO VGN-CR61B/P Battery
This high reflectivity is desirable in space-based UV spectrometers which have reduced mirror sizes due to space limitations. Osmium-coated mirrors were flown in several space missions aboard the Space Shuttle, but it soon became clear that the oxygen radicals in the low earth orbit are abundant enough to significantly deteriorate the osmium layer.[56] Sony VAIO VGN-CR61B/R Battery
Precautions
Finely divided metallic osmium is pyrophoric.[44] Osmium reacts with oxygen at room temperature forming volatile osmium tetroxide. Some osmium compounds are also converted to the tetroxide if oxygen is present.[44] This makes osmium tetroxide the main source of contact with the environment. Sony VAIO VGN-CR62B/L Battery
Osmium tetroxide is highly volatile and penetrates skin readily, and is very toxic by inhalation, ingestion, and skin contact.[57] Airborne low concentrations of osmium tetroxide vapor can cause lung congestion and skin or eye damage, and should therefore be used in a fume hood.[13] Sony VAIO VGN-CR62B/N Battery
Osmium tetroxide is rapidly reduced to relatively inert compounds by polyunsaturated vegetable oils, such as corn oil.[58]
Price
Osmium is usually sold as a 99% pure powder. Like other precious metals, it is measured by troy weight and by grams. Sony VAIO VGN-CR62B/P Battery
Its price at 2010 is about $400 per Troy ounce (or about $13 per gram), depending on the quantity and its supplier.[
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. Sony VAIO VGN-CR62B/R Battery
A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element (after osmium) and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts andhalogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable. Sony VAIO VGN-CR70B/W Battery
Iridium was discovered in 1803 among insoluble impurities in natural platinum. Smithson Tennant, the primary discoverer, named the iridium for the goddess Iris, personification of the rainbow, because of the striking and diverse colors of its salts. Sony VAIO VGN-CR71B/W Battery
Iridium is one of the rarest elements in the Earth's crust, with annual production and consumption of only threetonnes. 191Ir and 193Ir are the only two naturally occurring isotopes of iridium as well as the only stable isotopes; the latter is the more abundant of the two. Sony VAIO VGN-CR72B/W Battery
The most important iridium compounds in use are the salts and acids it forms with chlorine, though iridium also forms a number of organometallic compounds used in industrial catalysis, and in research. Iridium metal is employed when high corrosion resistance at high temperatures is needed, Sony VAIO VGN-CR90HS Battery
as in high-end spark plugs, crucibles for recrystallization of semiconductors at high temperatures, and electrodes for the production of chlorine in the chloralkali process. Iridium radioisotopes are used in some radioisotope thermoelectric generators. Sony VAIO VGN-CR90NS Battery
The unusually high abundance of iridium in the clay layer at the K–T geologic boundary gave rise to the Alvarez hypothesisthat the impact of a massive extraterrestrial object caused the extinction of dinosaurs and many other species 65 million years ago. Sony VAIO VGN-CR90S Battery
Iridium is found in meteorites with an abundance much higher than its average abundance in the Earth's crust. It is thought that the total amount of iridium in the planet Earth is much higher than that observed in crustal rocks, but as with other platinum group metals, the high density and tendency of iridium to bond with iron caused most iridium to descend below the crust when the planet was young and still molten. Sony VAIO VGN-CR92HS Battery
Physical properties
A member of the platinum group metals, iridium is white, resembling platinum, but with a slight yellowish cast. Because of its hardness, brittleness, and very high melting point (the ninth highest of all elements), solid iridium is difficult to machine, form, or work, and thus powder metallurgy is commonly employed instead. Sony VAIO VGN-CR92NS Battery
It is the only metal to maintain good mechanical properties in air at temperatures above 1600 °C.[4] Iridium has a very high boiling point (10th among all elements) and becomes a superconductor at temperatures below 0.14 K.[5]
Iridium's modulus of elasticity is the second highest among the metals, only being surpassed by osmium.[4] Sony VAIO VGN-CR92S Battery
This, together with a high modulus of rigidity and a very low figure for Poisson's ratio (the relationship of longitudinal to lateral strain), indicate the high degree of stiffness and resistance to deformation that have rendered its fabrication into useful components a matter of great difficulty. Sony VAIO VGN-CS118E/Q Battery
Despite these limitations and iridium's high cost, a number of applications have developed where mechanical strength is an essential factor in some of the extremely severe conditions encountered in modern technology.[4]
The measured density of iridium is only slightly lower (by about 0.12%) than that of osmium, the densest element known.[6][7] Sony VAIO VGN-CS118E/R Battery
There had been some ambiguity regarding which of the two elements was denser, due to the small size of the difference in density and difficulties in measuring it accurately,[8] but, with increased accuracy in factors used for calculating densityX-ray crystallographicdata yielded densities of 22.56 g/cm3 for iridium and 22.59 g/cm3 for osmium.[9] Sony VAIO VGN-CS118E/W Battery
Chemical properties
Iridium is the most corrosion-resistant metal known:[10] it is not attacked by almost any acid, aqua regia, molten metals or silicates at high temperatures. It can, however, be attacked by some molten salts, such as sodium cyanide and potassium cyanide,[10] as well as oxygen and the halogens (particularly fluorine)[11] at higher temperatures.[12] Sony VAIO VGN-CS11S/P Battery
Compounds
Iridium forms compounds in oxidation states between ?3 to +6; the most common oxidation states are +3 and +4.[3] Well-characterized examples of the highest oxidation state are rare, but includeIrF6 and two mixed oxides Sr2MgIrO6and Sr2CaIrO6.[3][13] Sony VAIO VGN-CS11S/Q Battery
In addition, it was reported in 2009 that iridium(VIII) tetroxide (IrO4) was prepared under matrix isolation conditions (6 K in Ar) by UV irradiation of an iridium-peroxo complex. This species, however, is not expected to be stable as a bulk solid at higher temperatures.[14] Sony VAIO VGN-CS11S/W Battery
Iridium dioxide, IrO2, a brown powder, is the only well-characterized oxide of iridium.[3] Asesquioxide, Ir2O3, has been described as a blue-black powder which is oxidized to IrO2 byHNO3.[11] The corresponding disulfides, diselenides, sesquisulfides and sesquiselenides are known and IrS3 has also been reported.[3] Sony VAIO VGN-CS11Z/R Battery
Iridium also forms iridates with oxidation states +4 and +5, such as K2IrO3 and KIrO3, which can be prepared from the reaction of potassium oxide or potassium superoxide with iridium at high temperatures.[15] Sony VAIO VGN-CS120J/P Battery
While no binary hydrides of iridium, IrxHy are known, complexes are known that contain IrH4?5 and IrH3?6, where iridium has the +1 and +3 oxidation states, respectively.[16] The ternary hydride Mg6Ir2H11 is believed to contain both the IrH4?
5 and the 18-electron IrH5?4 anion.[17] Sony VAIO VGN-CS120J/Q Battery
No monohalides or dihalides are known, whereas trihalides, IrX3, are known for all of the halogens.[3] For oxidation states +4 and above, only the tetrafluoride, pentafluoride and hexafluoride are known.[3] Iridium hexafluoride, IrF6, is a volatile and highly reactive yellow solid, composed of octahedral molecules. Sony VAIO VGN-CS120J/R Battery
It decomposes in water and is reduced to IrF4, a crystalline solid, by iridium black.[3] Iridium pentafluoride has similar properties but it is actually a tetramer, Ir4F20, formed by four corner-sharing octahedra.[3]
Hexachloroiridic(IV) acid, H2IrCl6, and its ammonium salt are the most important iridium compounds from an industrial perspective.[18] Sony VAIO VGN-CS190JTB Battery
They are involved in the purification of iridium and used as precursors for most other iridium compounds, as well as in the preparation of anode coatings. The IrCl2?
6 ion has an intense dark brown color, and can be readily reduced to the lighter-colored IrCl3?6 and vice versa.[18] Sony VAIO VGN-CS190JTP Battery
Iridium trichloride,IrCl3, which can be obtained in anhydrous form from direct oxidation of iridium powder bychlorine at 650 °C,[18] or in hydrated form by dissolving Ir2O3 in hydrochloric acid, is often used as a starting material for the synthesis of other Ir(III) compounds.[3] Sony VAIO VGN-CS190JTQ Battery
Another compound used as a starting material is ammonium hexachloroiridate(III), (NH4)3IrCl6. Iridium(III) complexes are diamagnetic (low-spin) and generally have an octahedral molecular geometry.[3]
Organoiridium compounds contain iridium–carbon bonds where the metal is usually in lower oxidation states. Sony VAIO VGN-CS190JTR Battery
For example, oxidation state zero is found in tetrairidium dodecacarbonyl, Ir4(CO)12, which is the most common and stable binary carbonylof iridium.[3] In this compound, each of the iridium atoms is bonded to the other three, forming a tetrahedral cluster. Some organometallic Ir(I) compounds are notable enough to be named after their discoverers. Sony VAIO VGN-CS190JTW Battery
One is Vaska's complex,IrCl(CO)[P(C6H5)3]2, which has the unusual property of binding to the dioxygen molecule, O2.[19] Another one is Crabtree's catalyst, a homogeneous catalyst for hydrogenation reactions.[20] These compounds are both square planar, d8 complexes, with a total of 16 valence electrons, which accounts for their reactivity.[21] Sony VAIO VGN-CS190NAB Battery
Iridium has two naturally occurring, stable isotopes, 191Ir and 193Ir, with natural abundances of 37.3% and 62.7%, respectively.[22] At least 34 radioisotopes have also been synthesized, ranging in mass number from 164 to 199. 192Ir, which falls between the two stable isotopes, is the most stable radioisotope, with a half-lifeof 73.827 days, Sony VAIO VGN-CS190NAC Battery
and finds application in brachytherapy[23] and in industrial radiography, particularly for non-destructive testing of welds in steel in the oil and gas industries; iridium-192 sources have been responsible for a number of radiological accidents. Three other isotopes have half-lives of at least a day—188Ir,189Ir, 190Ir.[22] Sony VAIO VGN-CS190NAD Battery
Isotopes with masses below 191 decay by some combination of ?+ decay, ? decay, and proton emission, with the exceptions of 189Ir, which decays byelectron capture, and 190Ir, which decays by positron emission. Synthetic isotopes heavier than 191 decay by ?? decay, although 192Ir also has a minor electron capture decay path.[22] Sony VAIO VGN-CS190NBB Battery
All known isotopes of iridium were discovered between 1934 and 2001; the most recent is 171Ir.[24]
At least 32 metastable isomers have been characterized, ranging in mass number from 164 to 197. Sony VAIO VGN-CS190NCA Battery
The most stable of these is 192m2Ir, which decays by isomeric transition with a half-life of 241 years,[22] making it more stable than any of iridium's synthetic isotopes in their ground states. The least stable isomer is190m3Ir with a half-life of only 2 µs.[22] The isotope 191Ir was the first one of any element to be shown to present a Mössbauer effect. Sony VAIO VGN-CS190NCB Battery
This renders it useful forMössbauer spectroscopy for research in physics, chemistry, biochemistry, metallurgy, and mineralogy.[25]
The discovery of iridium is intertwined with that of platinum and the other metals of the platinum group. Sony VAIO VGN-CS190NCC Battery
Native platinum used by ancient Ethiopians[26] and by South American cultures[27] always contained a small amount of the other platinum group metals, including iridium. Platinum reached Europe as platina ("small silver"), found in the 17th century by the Spanish conquerors in a region today known as the department of Chocó in Colombia.[ Sony VAIO VGN-CS50B/W Battery
The discovery that this metal was not an alloy of known elements, but instead a distinct new element, did not occur until 1748.[29]
Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids) to create soluble salts. Sony VAIO VGN-CS51B/W Battery
Sony VAIO VGN-CS52JB/W Battery
They always observed a small amount of a dark, insoluble residue.[4] Joseph Louis Proust thought that the residue was graphite.[4] The French chemists Victor Collet-Descotils, Antoine François, comte de Fourcroy, and Louis Nicolas Vauquelin also observed the black residue in 1803, but did not obtain enough for further experiments.[4] Sony VAIO VGN-CS60B/P Battery
In 1803, British scientist Smithson Tennant (1761–1815) analyzed the insoluble residue and concluded that it must contain a new metal. Vauquelin treated the powder alternately with alkali and acids[10] and obtained a volatile new oxide, which he believed to be of this new metal—which he named ptene, from the Greek word?????? (ptènos) for winged.[30][31] Sony VAIO VGN-CS60B/Q Battery
Tennant, who had the advantage of a much greater amount of residue, continued his research and identified the two previously undiscovered elements in the black residue, iridium and osmium.[4][10] He obtained dark red crystals (probably of Na2[IrCl6]·nH2O) by a sequence of reactions withsodium hydroxide and hydrochloric acid.[31] Sony VAIO VGN-CS60B/R Battery
He named iridium after Iris (????), the Greek winged goddess of the rainbow and the messenger of the Olympian gods, because many of the salts he obtained were strongly colored.[note 2][32] Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.[4][33] Sony VAIO VGN-CS61B/P Battery
British scientist John George Children was the first to melt a sample of iridium in 1813 with the aid of "the greatest galvanic battery that has ever been constructed" (at that time).[4] The first to obtain high purity iridium was Robert Hare in 1842. He found that it had a density of around 21.8 g/cm3 and noted that the metal is nearly unmalleable and very hard. Sony VAIO VGN-CS61B/Q Battery
The first melting in appreciable quantity was done by Henri Sainte-Claire Deville and Jules Henri Debray in 1860. They required burning more than 300 L of pure O2and H2 for each kilogram of iridium.[4]
These extreme difficulties in melting the metal limited the possibilities for handling iridium. Sony VAIO VGN-CS61B/R Battery
John Isaac Hawkins was looking to obtain a fine and hard point for fountain pen nibs and in 1834 managed to create an iridium-pointed gold pen. In 1880 John Hollandand William Lofland Dudley were able to melt iridium by adding phosphorus and patented the process in the United States; Sony VAIO VGN-CS62JB/P Battery
British company Johnson Matthey later stated that they had been using a similar process since 1837 and had already presented fused iridium at a number of World Fairs.[4] The first use of an alloy of iridium with ruthenium in thermocouples was made by Otto Feussner in 1933. These allowed for the measurement of high temperatures in air up to 2000 °C.[4] Sony VAIO VGN-CS62JB/Q Battery
In 1957 Rudolf Mössbauer, in what has been called one of the "landmark experiments in twentieth century physics",[34] discovered the resonant and recoil-free emission and absorption of gamma rays by atoms in a solid metal sample containing only 191Ir.[35] Sony VAIO VGN-CS62JB/R Battery
This phenomenon, known as the Mössbauer effect (which has since been observed for other nuclei, such as 57Fe), and developed asMössbauer spectroscopy, has made important contributions to research in physics, chemistry, biochemistry, metallurgy, and mineralogy.[25] Mössbauer received the Nobel Prize in Physics in 1961, just three years after he published his discovery.[36] Sony VAIO VGN-CS71B/W Battery
Occurrence
The Willamette Meteorite, the sixth-largest meteorite found in the world, has 4.7 ppm iridium.[37]
Iridium is one of the least abundant elements in the Earth's crust, having an average mass fraction of 0.001 ppm in crustal rock; Sony VAIO VGN-CS72JB/W Battery
goldis 40 times more abundant, platinum is 10 times more abundant, and silver and mercury are 80 times more abundant.[3]Telluriumis about as abundant as iridium, and only three naturally occurring elements are less abundant: rhenium, ruthenium, andrhodium, iridium being 10 times more abundant than the last two.[3] Sony VAIO VGN-CS90HS Battery
In contrast to its low abundance in crustal rock, iridium is relatively common in meteorites, with concentrations of 0.5 ppm or more.[38] It is thought that the overall concentration of iridium on Earth is much higher than what is observed in crustal rocks, but because of the density and siderophilic ("iron-loving") character of iridium, it descended below the crust and into the Earth's core when the planet was still molten.[18] Sony VAIO VGN-CS90NS Battery
Iridium is found in nature as an uncombined element or in natural alloys; especially the iridium–osmium alloys, osmiridium(osmium rich), and iridiosmium (iridium rich).[10] In the nickel and copper deposits the platinum group metals occur as sulfides(i.e. (Pt,Pd)S), tellurides (i.e. PtBiTe), antimonides (PdSb), and arsenides (i.e. PtAs2). Sony VAIO VGN-CS90S Battery
In all of these compounds platinum is exchanged by a small amount of iridium and osmium. As with all of the platinum group metals, iridium can be found naturally in alloys with raw nickel or raw copper.[39]
Within the Earth's crust, iridium is found at highest concentrations in three types of geologic structure: Sony VAIO VGN-CS91HS Battery
igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one of the former structures. The largest known primary reserves are in the Bushveld igneous complex in South Africa,[40] though the large copper–nickel deposits near Norilsk inRussia, and the Sudbury Basin in Canada are also significant sources of iridium. Sony VAIO VGN-CS91NS Battery
Smaller reserves are found in the United States.[40] Iridium is also found in secondary deposits, combined with platinum and other platinum group metals in alluvialdeposits. The alluvial deposits used by pre-Columbian people in the Chocó Department of Colombia are still a source for platinum-group metals. As of 2003 the world reserves had not been estimated.[10] Sony VAIO VGN-CS91S Battery
K–T boundary presence
The K–T boundary of 65 million years ago, marking the temporal border between the Cretaceous and Tertiary periods of geological time, was identified by a thin stratum of iridium-rich clay.[41] Sony VAIO VGN-CS92DS Battery
A team led by Luis Alvarez proposed in 1980 an extraterrestrial origin for this iridium, attributing it to an asteroid or comet impact.[41] Their theory, known as the Alvarez hypothesis, is now widely accepted to explain the demise of the dinosaurs. A large buried impact crater structure with an estimated age of about 65 million years was later identified under what is now the Yucatán Peninsula (the Chicxulub crater).[42][43] Sony VAIO VGN-CS92JS Battery
Dewey M. McLean and others argue that the iridium may have been of volcanic origin instead, as the Earth's core is rich in iridium, and active volcanoes such as Piton de la Fournaise, in the island of Réunion, are still releasing iridium.[44][45] Sony VAIO VGN-CS92XS Battery
Production
Iridium is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copperand nickel, noble metals such as silver, gold and the platinum group metals as well as selenium and tellurium settle to the bottom of the cell as anode mud, which forms the starting point for their extraction. Sony VAIO VGN-FW11E Battery
In order to separate the metals, they must first be brought into solution. Several methods are available depending on the separation process and the composition of the mixture; two representative methods are fusion with sodium peroxide followed by dissolution in aqua regia, and dissolution in a mixture of chlorinewith hydrochloric acid.[18][40] Sony VAIO VGN-FW11L Battery
After it is dissolved, iridium is separated from the other platinum group metals by precipitating (NH4)2IrCl6 or by extracting IrCl2?
6with organic amines.[50] The first method is similar to the procedure Tennant and Wollaston used for their separation. Sony VAIO VGN-FW11M Battery
The second method can be planned as continuous liquid–liquid extraction and is therefore more suitable for industrial scale production. In either case, the product is reduced using hydrogen, yielding the metal as a powder or sponge that can be treated using powder metallurgytechniques.[51][52] Sony VAIO VGN-FW11S Battery
Annual production of iridium circa 2000 was around 3 tonnes or about 100,000 troy ounces (ozt).[note 3][10] The price of iridium as of 2007 was $440 USD/ozt,[46] but the price fluctuates considerably, as shown in the table. Sony VAIO VGN-FW11ZU Battery
The high volatility of the prices of the platinum group metals has been attributed to supply, demand, speculation, and hoarding, amplified by the small size of the market and instability in the producing countries.[53] Sony VAIO VGN-FW139E/H Battery
Applications
The global demand for iridium in 2007 was 119,000 troy ounces (3,700 kg), out of which 25,000 ozt (780 kg) were used for electrical applications such as spark plugs; 34,000 ozt (1,100 kg) for electrochemical applications such as electrodes for the chloralkali process; 24,000 ozt (750 kg) for catalysis; and 36,000 ozt (1,100 kg) for other uses.[54] Sony VAIO VGN-FW140AE Battery
Industrial and medical
The high melting point, hardness and corrosion resistance of iridium and its alloys determine most of its applications. Iridium and especially iridium–platinum alloys or osmium–iridium alloys have a low wear and are used, for example, for multi-pored spinnerets, through which a plastic polymer melt is extruded to form fibers, such as rayon.[55] Sony VAIO VGN-FW140D Battery
Osmium–iridium is used for compass bearings and for balances.[10]
Corrosion and heat resistance makes iridium an important alloying agent. Certain long-life aircraft engine parts are made of an iridium alloy and an iridium–titanium alloy is used for deep-water pipes because of its corrosion resistance.[10] Sony VAIO VGN-FW140E Battery
Iridium is also used as a hardening agent in platinum alloys. The Vickers hardness of pure platinum is 56 HV while platinum with 50% of iridium can reach over 500 HV.[56][57]
Devices that must withstand extremely high temperatures are often made from iridium. Sony VAIO VGN-FW140E/H Battery
For example, high-temperature cruciblesmade of iridium are used in the Czochralski process to produce oxide single-crystals (such as sapphires) for use in computer memory devices and in solid state lasers.[58][59] The crystals, such as gadolinium gallium garnet and yttrium gallium garnet, are grown by melting pre-sintered charges of mixed oxides under oxidizing conditions at temperatures up to 2100 °C.[4] Sony VAIO VGN-FW140E/W Battery
Its resistance to arc erosion makes iridium alloys ideal for electrical contacts for spark plugs.[59][60]
Iridium compounds are used as catalysts in the Cativa process for carbonylation of methanol to produce acetic acid.[61] Iridium itself is used as a catalyst in a type of automobile engine introduced in 1996 called the direct-ignition engine.[10] Sony VAIO VGN-FW140FE Battery
The radioisotope iridium-192 is one of the two most important sources of energy for use in industrial ?-radiography for non-destructive testing of metals.[62][63]Additionally, 192Ir is used as a source of gamma radiation for the treatment of cancer using brachytherapy, a form of radiotherapy where a sealed radioactive source is placed inside or next to the area requiring treatment. Sony VAIO VGN-FW140N Battery
Specific treatments include high dose rate prostate brachytherapy, bilary duct brachytherapy, and intracavitary cervix brachytherapy.[10]
Scientific
An alloy of 90% platinum and 10% iridium was used in 1889 to construct the International Prototype Meter and kilogram mass, kept by the International Bureau of Weights and Measures near Paris.[10] Sony VAIO VGN-FW140N/W Battery
The meter bar was replaced as the definition of the fundamental unit of length in 1960 by a line in the atomic spectrum of krypton,[note 4][64] but the kilogram prototype is still the international standard of mass.[65]
Iridium has been used in the radioisotope thermoelectric generators of unmanned spacecraft such as the Voyager, Viking, Pioneer,Cassini, Galileo, and New Horizons. Sony VAIO VGN-FW145E Battery
Iridium was chosen to encapsulate the plutonium-238 fuel in the generator because it can withstand the operating temperatures of up to 2000 °C and for its great strength.[4]
Another use concerns X-ray optics, especially X-ray telescopes.[66] The mirrors of the Chandra X-ray Observatory are coated with a layer of iridium 60 nm thick. Sony VAIO VGN-FW145E/W Battery
Iridium proved to be the best choice for reflecting X-rays after nickel, gold, and platinum were also tested. The iridium layer, which had to be smooth to within a few atoms, was applied by depositing iridium vapor under high vacuumon a base layer of chromium.[67] Sony VAIO VGN-FW160AE Battery
Iridium is used in particle physics for the production of antiprotons, a form of antimatter. Antiprotons are made by shooting a high-intensity proton beam at aconversion target, which needs to be made from a very high density material. Although tungsten may be used instead, iridium has the advantage of better stability under the shock waves induced by the temperature rise due to the incident beam.[68] Sony VAIO VGN-FW160D Battery
Carbon–hydrogen bond activation (C–H activation) is an area of research on reactions that cleave carbon–hydrogen bonds, which were traditionally regarded as unreactive. The first reported successes at activating C–H bonds in saturated hydrocarbons, published in 1982, used organometallic iridium complexes that undergo an oxidative addition with the hydrocarbon.[69][70] Sony VAIO VGN-FW160E Battery
Iridium complexes are being investigated as catalysts for asymmetric hydrogenation. These catalysts have been used in the synthesis of natural products and able to hydrogenate certain difficult substrates, such as unfunctionalized alkenes, enantioselectively (generating only one of the two possible enantiomers).[71][72]
Iridium forms a variety of complexes of fundamental interest in triplet harvesting.[73][74][75] Sony VAIO VGN-FW160E/H Battery
Historical
Iridium–osmium alloys were used to tip fountain pen nibs. The first major use of iridium was in 1834 in nibs mounted on gold.[4]Since 1944, the famous Parker 51 fountain pen was fitted with a nib tipped by a ruthenium and iridium alloy (with 3.8% iridium). Sony VAIO VGN-FW160F/E Battery
The tip material in modern fountain pens is still conventionally called "iridium," although there is seldom any iridium in it; other metals such as tungsten have taken its place.[76]
An iridium–platinum alloy was used for the touch holes or vent pieces of cannon. Sony VAIO VGN-FW170J/H Battery
According to a report of the Paris Exhibition of 1867, one of the pieces being exhibited by Johnson and Matthey "has been used in a Withworth gun for more than 3000 rounds, and scarcely shows signs of wear yet. Those who know the constant trouble and expense which are occasioned by the wearing of the vent-pieces of cannon when in active service, will appreciate this important adaptation".[77] Sony VAIO VGN-FW180AE Battery
The pigment iridium black, which consists of very finely divided iridium, is used for painting porcelain an intense black; it was said that "all other porcelain black colors appear grey by the side of it".[78]
Precautions
Iridium in bulk metallic form is not biologically important or hazardous to health due to its lack of reactivity with tissues; Sony VAIO VGN-FW180D Battery
there are only about 20 parts per trillion of iridium in human tissue.[10] However, finely divided iridium powder can be hazardous to handle, as it is an irritant and may ignite in air.[40] Very little is known about the toxicity of iridium compounds because they are used in very small amounts, but soluble salts, such as the iridium halides, could be hazardous due to elements other than iridium or due to iridium itself.[23] Sony VAIO VGN-FW180E Battery
However, most iridium compounds are insoluble, which makes absorption into the body difficult.[10]
A radioisotope of iridium, 192Ir, is dangerous like other radioactive isotopes. The only reported injuries related to iridium concern accidental exposure to radiation from 192Ir used in brachytherapy.[23] Sony VAIO VGN-FW180E/H Battery
High-energy gamma radiation from 192Ir can increase the risk of cancer. External exposure can cause burns, radiation poisoning, and death. Ingestion of 192Ir can burn the linings of the stomach and the intestines.[79] 192Ir, 192mIr, and 194mIr tend to deposit in the liver, and can pose health hazards from both gamma and beta radiation. Sony VAIO VGN-FW180FU Battery
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River."[1]It is a dense, malleable, ductile, precious, gray-white transition metal. Sony VAIO VGN-FW190EBH Battery
Even though it has six naturally occurring isotopes, platinum is one of the rarest elements in the Earth's crust and has an average abundance of approximately 0.005 mg/kg. It is the least reactive metal. It occurs in some nickeland copper ores along with some native deposits, mostly in South Africa, which accounts for 80% of the world production. Sony VAIO VGN-FW190ECH Battery
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. Sony VAIO VGN-FW190EDH Battery
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. Sony VAIO VGN-FW190NAH Battery
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. Sony VAIO VGN-FW190NBH Battery
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. Its compounds, most notablycisplatin, are applied in chemotherapy against certain types of cancer.[2]
Physical
As a pure metal, platinum is silvery-white, lustrous, ductile, and malleable.[ Sony VAIO VGN-FW190NCH Battery
Platinum is more ductile than gold, silver and copper, thus being the most ductile of pure metals, but gold is still more malleable than platinum [4] [5] It does not oxidize at any temperature, although it is corroded by halogens, cyanides, sulfur, and caustic alkalis. Platinum is insoluble in hydrochloricand nitric acid, but dissolves in aqua regia to form chloroplatinic acid, H2PtCl6.[6] Sony VAIO VGN-FW190NDH Battery
Platinum's resistance to wear and tarnish is well suited for making fine jewelry. The metal has an excellent resistance to corrosion and high temperature and has stable electrical properties. All of these characteristics have been used for industrial applications.[7]
Chemical
The most common oxidation states of platinum are +2 and +4. Sony VAIO VGN-FW190NEH Battery
The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) species. As is expected, tetracoordinate platinum(II) compounds tend to adopt 16-electronsquare planar geometries. While elemental platinum is generally unreactive, it dissolves in aqua regia to give soluble hexachloroplatinic acid ("H2PtCl6", formally (H3O)2PtCl6·nH2O ):[8] Sony VAIO VGN-FW198U/H Battery
Pt + 4 HNO3 + 6 HCl ? H2PtCl6 + 4 NO2 + 4 H2O
As a soft acid, platinum has a great affinity for sulfur, such as on dimethyl sulfoxide(DMSO); numerous DMSO complexes have been reported and care should be taken in the choice of reaction solvent.[9] Sony VAIO VGN-FW260J/B Battery
Platinum has six naturally occurring isotopes: 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt. The most abundant of these is195Pt, comprising 33.83% of all platinum. It is the only stable isotope with a non-zero spin; with a spin of 1/2, 195Pt satellite peaks are often observed in 1H and 31P NMR spectroscopy (i.e. Pt-phosphine and Pt-alkyl complexes). Sony VAIO VGN-FW280J/H Battery
190Pt is the least abundant at only 0.01%. Of the naturally occurring isotopes, only 190Pt is unstable, though it decays with a half-life of 6.5×1011 years. 198Pt undergoes alpha decay, but because its half-life is estimated at longer than 3.2×1014 years, it is considered stable. Sony VAIO VGN-FW290JRB Battery
Platinum also has 31 synthetic isotopes ranging in atomic mass from 166 to 202, making the total number of known isotopes 37. The least stable of these is 166Pt with a half-life of 300 µs, while the most stable is 193Pt with a half-life of 50 years. Most platinum isotopes decay by some combination of beta decay and alpha decay. 188Pt, 191Pt, and 193Pt decay primarily by electron capture. 190Pt and 198Pt have double beta decay paths.[10] Sony VAIO VGN-FW290JTB Battery
Occurrence
Platinum is an extremely rare metal,[11] occurring at a concentration of only 0.005 ppm in the Earth's crust.[12][13] It is sometimes mistaken for silver (Ag). Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridium. Sony VAIO VGN-FW290JTH Battery
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.[6] Sony VAIO VGN-FW290JTW Battery
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. Sony VAIO VGN-FW355J/H Battery
AtPlatinum, Alaska, about 545,000 troy ounces had been mined between 1927 and 1975. The mine ceased operations in 1990.[14] The rare sulfide mineral cooperite, (Pt,Pd,Ni)S, contains platinum along with palladium and nickel. Cooperite occurs in theMerensky Reef within the Bushveld complex, Gauteng, South Africa.[15] Sony VAIO VGN-FW373J/B Battery
In 1865, chromites were identified in the Bushveld region of South Africa, followed by the discovery of platinum in 1906.[16]The largest known primary reserves are in the Bushveld complex in South Africa.[17] The large copper–nickel deposits nearNorilskin Russia, and the Sudbury Basin, Canada, are the two other large deposits. Sony VAIO VGN-FW30B Battery
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,[17]for example in the Absaroka Range in Montana.[18] In 2009, South Africa was the top producer of platinum, with an almost 80% share, followed by Russia at 11%.[19] Sony VAIO VGN-FW50B Battery
In 2010 July its been announced that Platinum is present in the state of Tamil nadu, India[20] and a MOU has been signed between Geological Survey of India with TAMIN - Tamilnadu Minerals Ltd.[21]
Platinum exists in higher abundances on the Moon and in meteorites. Sony VAIO VGN-FW51B/W Battery
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.[22] Sony VAIO VGN-FW51MF Battery
Compounds
Hexachloroplatinic acid mentioned above is probably the most important platinum compound, as it serves as the precursor for many other platinum compounds. By itself, it has various applications in photography, zinc etchings, indelible ink, plating, mirrors, porcelain coloring, and as a catalyst.[23] Sony VAIO VGN-FW51MF/H Battery
Treatment of hexachloroplatinic acid with an ammonium salt, such as ammonium chloride, gives ammonium hexachloroplatinate,[8]which is relatively insoluble in ammonium solutions. Heating this ammonium salt in the presence of hydrogen reduces it to elemental platinum. Sony VAIO VGN-FW51ZF Battery
Potassium hexachloroplatinate is similarly insoluble, and hexachloroplatinic acid has been used in the determination of potassium ions by gravimetry.[24]
When hexachloroplatinic acid is heated, it decomposes through platinum(IV) chloride and platinum(II) chloride to elemental platinum, although the reactions do not occur stepwise:[25] Sony VAIO VGN-FW51ZF/H Battery
(H3O)2PtCl6·nH2O PtCl4 + 2 HCl + (n + 2) H2O
PtCl4 PtCl2 + Cl2
PtCl2 Pt + Cl2
All three reactions are reversible. Platinum(II) and platinum(IV) bromides are known as well. Platinum hexafluoride is a strong oxidizer capable of oxidizing oxygen. Sony VAIO VGN-FW52JB Battery
Oxides
Platinum(IV) oxide, PtO2, also known as Adams' catalyst, is a black powder which is soluble in KOH solutions and concentrated acids.[26] PtO2 and the less common PtO both decompose upon heating.[3] Platinum(II,IV) oxide, Pt3O4, is formed in the following reaction: Sony VAIO VGN-FW54FB Battery
2 Pt2+ + Pt4+ + 4 O2? ? Pt3O4
Platinum also forms a trioxide, where it is present in the +4 oxidation state.
Other compounds
Unlike palladium acetate, platinum(II) acetate is not commercially available. Where a base is desired, the halides have been used in conjunction with sodium acetate.[9] The use of platinum(II) acetylacetonate has also been reported.[27] Sony VAIO VGN-FW70DB Battery
Several barium platinides have been synthesized in which platinum exhibits negative oxidation states ranging from ?1 to ?2. These include BaPt, Ba3Pt2, andBa2Pt.[28] Caesium platinide, Cs2Pt, a dark-red transparent crystalline compound[29] has been shown to contain Pt2?anions.[30] Sony VAIO VGN-FW71DB/W Battery
Platinum also exhibits negative oxidation states at surfaces reduced electrochemically.[31] The negative oxidation states exhibited by platinum are unusual for metallic elements, and they are attributed to the relativistic stabilization of the 6s orbitals.[30]
Zeise's salt, containing an ethylene ligand, was one of the first organometallic compounds discovered. Sony VAIO VGN-FW72JGB Battery
Dichloro(cycloocta-1,5-diene)platinum(II) is a commercially available olefin complex, which contains easily displaceable cod ligands ("cod" being an abbreviation of 1,5-cyclooctadiene). The cod complex and the halides are convenient starting points to platinum chemistry.[9] Sony VAIO VGN-FW73JGB Battery
Cisplatin, or cis-diamminedichloroplatinum(II) is the first of a series of square planar platinum(II)-containing chemotherapy drugs, including carboplatin andoxaliplatin. These compounds are capable of crosslinking DNA, and kill cells by similar pathways to alkylating chemotherapeutic agents.[32] Sony VAIO VGN-FW74FB Battery
Platinum occurs naturally in the alluvial sands of various rivers, though there is little evidence of its use by ancient people. However, the metal was used by pre-Columbian Americans near modern-day Esmeraldas, Ecuador to produce artifacts of a white gold-platinum alloy. Sony VAIO VGN-FW81HS Battery
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."[33]
In 1741, Charles Wood, a British metallurgist, found various samples of Colombian platinum in Jamaica, which he sent to William Brownrigg for further investigation. Sony VAIO VGN-FW81NS Battery
Antonio de Ulloa, also credited with the discovery of platinum, returned to Spain from the French Geodesic Mission in 1746 after having been there for eight years. His historical account of the expedition included a description of platinum as being neither separable norcalcinable. Ulloa also anticipated the discovery of platinum mines. Sony VAIO VGN-FW81S Battery
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 inHuancavelica.[33]
In 1750, after studying the platinum sent to him by Wood, Brownrigg presented a detailed account of the metal to the Royal Society, mentioning that he had seen no mention of it in any previous accounts of known minerals.[34Sony VAIO VGN-FW82DS Battery
Brownrigg also made note of platinum's extremely high melting point and refractoriness towardborax. Other chemists across Europe soon began studying platinum, including 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. Sony VAIO VGN-FW82JS Battery
Scheffer described platinum as being less pliable than gold, but with similar resistance to corrosion.[33]
Carl von Sickingen researched platinum extensively in 1772. He succeeded in making malleable platinum by alloying it with gold, dissolving the alloy in aqua regia,
precipitating the platinum with ammonium chloride, igniting the ammonium chloroplatinate, and hammering the resulting finely divided platinum to make it cohere. Franz Karl Achard made the first platinum crucible in 1784. He worked with the platinum by fusing it with arsenic, then later volatilizing the arsenic.[33] Sony VAIO VGN-FW82XS Battery
Since the other platinum family members were not discovered yet (platinum was the first in the list), Scheffer and Sickingen made the false assumption that due to it's hardness -which is slightly more than for pure iron , platinum was a relatively non pliable material, even brittle at times, when in fact it's ductility and malleability are close to that of gold. Sony VAIO VGN-FW83DS Battery
Their assumptions could not be avoided since the platinum they experimented with was highly contaminated with minute amounts of the platinum family elements such as Osmium and Iridium amongst others, which embrittled the platinum alloy. Sony VAIO VGN-FW83JS Battery
Alloying this impure platinum residue called "plyoxen" with gold was the only solution at the time to obtain a pliable compound, but nowadays, very pure platinum is available and extremely long wire can be drawn from pure platinum, very easily, due to it's crystalline structure which is similar to that of many soft metals.[35] Sony VAIO VGN-FW83XS Battery
In 1786, Charles III of Spain provided a library and laboratory to Pierre-François Chabaneau to aid in his research of platinum. Chabaneau succeeded in removing various impurities from the ore, including gold, mercury, lead, copper, and iron. This led him to believe he was working with a single metal, but in truth the ore still contained the yet-undiscovered platinum group metals. Sony VAIO VGN-FW90HS Battery
Sony VAIO VGN-FW90NS Battery
This led to inconsistent results in his experiments. At times, the platinum seemed malleable, but when it was alloyed with iridium, it would be much more brittle. Sometimes the metal was entirely incombustible, but when alloyed with osmium, it would volatilize. After several months, Chabaneau succeeded in producing 23 kilograms of pure, malleable platinum by hammering and compressing the sponge form while white-hot. Sony VAIO VGN-FW90S Battery
Chabeneau realized the infusibility of platinum would lend value to objects made of it, and so started a business with Joaquín Cabezas producing platinum ingots and utensils. This started what is known as the "platinum age" in Spain.[33]
In 2007, Gerhard Ertl won the Nobel Prize in Chemistry for determining the detailed molecular mechanisms of the catalytic oxidation of carbon monoxide over platinum (catalytic converter).[36] Sony VAIO VGN-FW91NS Battery
Production
Platinum, along with the rest of the platinum metals, is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper, noble metals such as silver, gold and the platinum group metals as well as seleniumand tellurium settle to the bottom of the cell as "anode mud", which forms the starting point for the extraction of the platinum group metals. Sony VAIO VGN-FW91S Battery
If pure platinum is found in placer deposits or other ores, it is isolated from them by various methods of subtracting impurities. Because platinum is significantly denser than many of its impurities, the lighter impurities can be removed by simply floating them away in a liquid. Platinum is also nonmagnetic, while nickel and iron are both magnetic. Sony VAIO VGN-FW92DS Battery
These two impurities are thus removed by running an electromagnet over the mixture. Because platinum has a higher melting point than most other substances, many impurities can be burned or melted away without melting the platinum. Finally, platinum is resistant to hydrochloric and sulfuric acids, while other substances are readily attacked by them. Sony VAIO VGN-FW92JS Battery
Metal impurities can be removed by stirring the mixture in either of the two acids and recovering the remaining platinum.[39]
One suitable method for purification for the raw platinum, which contains platinum, gold, and the other platinum group metals, is to process it with aqua regia, in which palladium, Sony VAIO VGN-FW93DS Battery
gold and platinum are dissolved, while osmium, iridium, ruthenium and rhodium stay unreacted. The gold is precipitated by the addition of iron(III) chloride and after filtering off the gold, the platinum is precipitated as ammonium chloroplatinate by the addition of ammonium chloride. Ammonium chloroplatinate can be converted to the metal by heating.[40] Sony VAIO VGN-FW93JS Battery
Applications
Of the 239 tonnes of platinum sold in 2006, 130 tonnes were used for vehicle emissions control devices, 49 tonnes for jewelry, 13.3 tonnes in electronics, and 11.2 tonnes in the chemical industry as a catalyst. The remaining 35.5 tonnes went to various other minor applications, such as electrodes, anticancer drugs, oxygen sensors, spark plugs and turbine engines.[41] Sony VAIO VGN-FW93XS Battery
Catalysis
The most common use of platinum is as a catalyst in chemical reactions, many times as platinum black. It has been employed in this application since the early 19th century, when platinum powder was used to catalyze the ignition of hydrogen. Sony VAIO VGN-FW94FS Battery
Its most important application is in automobiles as a catalytic converter, which allows the complete combustion of low concentrations of unburned hydrocarbons from the exhaust into carbon dioxide and water vapor. Platinum is also used in the petroleum industry as a catalyst in a number of separate processes, Sony VAIO VGN-FW94GS Battery
but especially in catalytic reforming of straight run naphthas into higher-octane gasoline which becomes rich in aromatic compounds. PtO2, also known as Adams' catalyst, is used as a hydrogenation catalyst, specifically for vegetable oils.[23] Platinum metal also strongly catalyzes the decomposition of hydrogen peroxide into water and oxygen gas.[42] Sony VAIO VGN-FW94HS Battery
Standard
From 1889 to 1960, the meter was defined as the length of a platinum-iridium (90:10) alloy bar, known as the International Prototype Meter bar. The previous bar was made of platinum in 1799. The International Prototype Kilogram remains defined by a cylinder of the same platinum-iridium alloy made in 1879.[43] Sony VAIO VGN-G118CN Battery
The standard hydrogen electrode also uses a platinized platinum electrode due to its corrosion resistance, and other attributes.[44]
Precious metal
Platinum is a precious metal commodity; its bullion has the ISO currency code of XPT. Coins, bars, and ingots are traded or collected. Sony VAIO VGN-G118GN/B Battery
Platinum finds use in jewelry, usually as a 90–95% alloy, due to its inertness and shine. Jewelry trade publications advise jewelers to present minute surface scratches (which they term patina) as a desirable feature.[45][46]
In watchmaking, Vacheron Constantin, Patek Philippe, Rolex, Breitling, and other companies use platinum for producing their limited edition watch series. Sony VAIO VGN-G118GN/T Battery
Watchmakers appreciate the unique properties of platinum, as it neither tarnishes nor wears out (relative to gold).[47]
Average price of platinum from 1991 to 2007 in US$ per troy ounce(~$20/g)[48]
The price of platinum, like other industrial commodities, is more volatile than that of gold. Sony VAIO VGN-G118TN/B Battery
In 2008, the price of platinum dropped from $2,252 to $774 per oz,[49] a loss of nearly 2/3 of its value. By contrast, the price of gold dropped from ~$1,000 to ~$700/ozt during the same time frame, a loss of only 1/3 of its value.
During periods of sustained economic stability and growth, the price of platinum tends to be as much as twice the price of gold, Sony VAIO VGN-G118TN/S Battery
whereas during periods of economic uncertainty,[50] the price of platinum tends to decrease due to reduced industrial demand, falling below the price of gold. Gold prices are more stable in slow economic times, as gold is considered a safe haven and gold demand is not driven by industrial uses. In the 18th century, platinum's rarity made King Louis XV of France declare it the only metal fit for a king.[51] Sony VAIO VGN-G11VN/T Battery
Other uses
In the laboratory, platinum wire is used for electrodes; platinum pans and supports are used in thermogravimetric analysisbecause of the stringent requirements of chemical inertness upon heating to high temperatures (~1000 °C). Sony VAIO VGN-G11VN/TC Battery
Platinum is used as an alloying agent for various metal products, including fine wires, noncorrosive laboratory containers, medical instruments, dental prostheses, electrical contacts, and thermocouples. Platinum-cobalt, an alloy of roughly three parts platinum and one part cobalt, is used to make relatively strong permanent magnets.[23] Sony VAIO VGN-G11XN/B Battery
Platinum-based anodes are used in ships, pipelines, and steel piers.[6]
Symbol of prestige
Platinum's rarity as a metal has caused advertisers to associate it with exclusivity and wealth. "Platinum" debit cards have greater privileges than do "gold" ones.[52] Sony VAIO VGN-G1AAPS Battery
"Platinum awards" are the second highest possible, ranking above "gold", "silver" and "bronze", but below diamond. For example, in the United States, a musical album that has sold more than 1 million copies, will be credited as "platinum", whereas an album that sold more than 10 million copies will be certified as "diamond".[53] Sony VAIO VGN-G1AAPSA Battery
Some products, such as blenders and vehicles, with a silvery-white color 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 frame of the Crown of Queen Elizabeth the Queen Mother, manufactured for her coronation as Consort of King George VI, is made of platinum. It was the first British crown to be made of this particular metal.[54] Sony VAIO VGN-G1AAPSB Battery
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 both respiratory and skin allergies. The current OSHA standard is 2 micrograms per cubic meter of air averaged over an 8-hour work shift.[55] Sony VAIO VGN-G1AAPSC Battery
Certain platinum complexes are used in chemotherapy, and show good activity against some tumors. Cisplatin is particularly effective against testicular cancer; the cure rate was improved from 10% to 85%.[56] However, the side effects are severe. Cisplatin causes cumulative, irreversible kidney damage and deafness.[57] Sony VAIO VGN-G1ABNS Battery
As with other ototoxic agents, deafness may be secondary to interactions with melanin in the stria vascularis. Binding of platinum to RNA has been reviewed.Sony VAIO VGN-G1KBN Battery
As platinum is a catalyst in the manufacture of the silicone rubber and gel components of several types of medical implants (breast implants, joint replacement prosthetics, artificial lumbar discs, vascular access ports, etc.), the possibility platinum could enter the body and cause adverse effects has merited study. Sony VAIO VGN-G1KAP Battery
TheFood and Drug Administration and other institutions have reviewed the issue and found no evidence to suggest toxicity in vivo.Sony VAIO VGN-G1KBNA Battery,Sony VAIO VGN-G1LAP Battery,Sony VAIO VGN-G1LBN Battery,Sony VAIO VGN-G218LN/T Battery,Sony VAIO VGN-G218N/B Battery
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