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definitions - Iridium

iridium (n.)

1.a heavy brittle metallic element of the platinum group; used in alloys; occurs in natural alloys with platinum or osmium

Iridium (n.)

1.(MeSH)A metallic element with the atomic symbol Ir, atomic number 77, and atomic weight 192.22.

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Merriam Webster

iridiumi*rid"i*um (�*rĭd"ĭ*ŭm), n. [NL., fr. L. iris, iridis, the rainbow. So called from the iridescence of some of its solutions. See Iris.] (Chem.) A rare metallic element of atomic number 77, of the same group as platinum, which it much resembles, being silver-white and indifferent to most corrosive agents, but harder, more brittle, and with a higher melting temperature (2410° C, versus platinum 1772° C). With the exception of osmium, it is the heaviest substance known, its specific gravity being 22.4. Symbol Ir. Atomic weight 192.22.

☞ Iridium usually occurs as a native alloy with osmium (iridosmine or osmiridium), which may occur alone or with platinum. Iridium, as an alloy with platinum, is used in bushing the vents of heavy ordnance. It is also used for the points of gold pens, and in a finely powdered condition (iridium black), for painting porcelain black.

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synonyms - Iridium

iridium (n.)

atomic number 77, Ir

see also - Iridium

iridium (n.)

iridic

phrases

-Eka-Iridium • Eka-iridium • Iridium (disambiguation) • Iridium 33 • Iridium Jazz Club • Iridium Satellite LLC • Iridium anomaly • Iridium chloride • Iridium satellite constellation • Iridium(III) chloride • Iridium(IV) fluoride • Iridium(IV) oxide • Iridium(V) fluoride • Iridium(VI) fluoride • Iridium-164 • Iridium-165 • Iridium-166 • Iridium-167 • Iridium-168 • Iridium-169 • Iridium-170 • Iridium-171 • Iridium-172 • Iridium-173 • Iridium-174 • Iridium-175 • Iridium-176 • Iridium-177 • Iridium-178 • Iridium-179 • Iridium-180 • Iridium-181 • Iridium-182 • Iridium-183 • Iridium-184 • Iridium-185 • Iridium-186 • Iridium-187 • Iridium-188 • Iridium-189 • Iridium-190 • Iridium-191 • Iridium-192 • Iridium-193 • Iridium-194 • Iridium-195 • Iridium-196 • Iridium-197 • Iridium-198 • Iridium-199 • Isotopes of iridium • Pentamethylcyclopentadienyl iridium dichloride dimer

analogical dictionary

Wikipedia - see also

Wikipedia

Iridium

                   
osmiumiridiumplatinum
Rh

Ir

Mt
Appearance
silvery white
Two square pieces of gray foil
General properties
Name, symbol, number iridium, Ir, 77
Pronunciation /ɨˈrɪdiəm/
i-RID-ee-əm
Element category transition metal
Group, period, block 96, d
Standard atomic weight 192.217
Electron configuration [Xe] 4f14 5d7 6s2
Electrons per shell 2, 8, 18, 32, 15, 2 (Image)
Physical properties
Phase solid
Density (near r.t.) 22.56 [1] g·cm−3
Liquid density at m.p. 19 g·cm−3
Melting point 2739 K, 2466 °C, 4471 °F
Boiling point 4701 K, 4428 °C, 8002 °F
Heat of fusion 41.12 kJ·mol−1
Heat of vaporization 563 kJ·mol−1
Molar heat capacity 25.10 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2713 2957 3252 3614 4069 4659
Atomic properties
Oxidation states −3,−1, 0, 1, 2, 3, 4, 5, 6
Electronegativity 2.20 (Pauling scale)
Ionization energies 1st: 880 kJ·mol−1
2nd: 1600 kJ·mol−1
Atomic radius 136 pm
Covalent radius 141±6 pm
Miscellanea
Crystal structure face-centered cubic
Magnetic ordering paramagnetic[2]
Electrical resistivity (20 °C) 47.1 nΩ·m
Thermal conductivity 147 W·m−1·K−1
Thermal expansion 6.4 µm/(m·K)
Speed of sound (thin rod) (20 °C) 4825 m·s−1
Young's modulus 528 GPa
Shear modulus 210 GPa
Bulk modulus 320 GPa
Poisson ratio 0.26
Mohs hardness 6.5
Vickers hardness 1760 MPa
Brinell hardness 1670 MPa
CAS registry number 7439-88-5
Most stable isotopes
Main article: Isotopes of iridium
iso NA half-life DM DE (MeV) DP
188Ir syn 1.73 d ε 1.64 188Os
189Ir syn 13.2 d ε 0.532 189Os
190Ir syn 11.8 d ε 2.000 190Os
191Ir 37.3% 191Ir is stable with 114 neutrons
192Ir syn 73.827 d β 1.460 192Pt
ε 1.046 192Os
192m2Ir syn 241 y IT 0.161 192Ir
193Ir 62.7% 193Ir is stable with 116 neutrons
193mIr syn 10.5 d IT 0.080 193Ir
194Ir syn 19.3 h β 2.247 194Pt
194m2Ir syn 171 d IT  ? 194Ir
· r

Iridium (play /ɨˈrɪdiəm/ i-RID-ee-əm) is the chemical element with atomic number 77, and is represented by the symbol Ir. 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 and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable.

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. Iridium is one of the rarest elements in the Earth's crust, with annual production and consumption of only three tonnes. 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.

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, 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.

Iridium is found in meteorites with an abundance much higher than its average abundance in the Earth's crust. For this reason the unusually high abundance of iridium in the clay layer at the Cretaceous–Paleogene boundary gave rise to the Alvarez hypothesis that the impact of a massive extraterrestrial object caused the extinction of dinosaurs and many other species 65 million years ago. 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.

Contents

  Characteristics

  Physical properties

A flattened drop of dark gray substance.
  1 troy ounce (31 g) of arc-melted iridium

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.[3] 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] This, together with a high shear modulus 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. 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] 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 density X-ray crystallographic data yielded densities of 22.56 g/cm3 for iridium and 22.59 g/cm3 for osmium.[9]

  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]

  Compounds

Oxidation states[note 1]
−3 [Ir(CO)3]3−
−1 [Ir(CO)3(PPh3)]
0 Ir4(CO)12
+1 [Ir(CO)Cl(PPh3)2]
+2 IrCl2
+3 IrCl3
+4 IrO2
+5 Ir4F20
+6 IrF6

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 include IrF6 and two mixed oxides Sr2MgIrO6 and Sr2CaIrO6.[3][13] 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]

Iridium dioxide, IrO2, a brown powder, is the only well-characterized oxide of iridium.[3] A sesquioxide, Ir2O3, has been described as a blue-black powder which is oxidized to IrO2 by HNO3.[11] The corresponding disulfides, diselenides, sesquisulfides and sesquiselenides are known and IrS3 has also been reported.[3] 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]

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]

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. 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] 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] Iridium trichloride, IrCl3, which can be obtained in anhydrous form from direct oxidation of iridium powder by chlorine 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] 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. For example, oxidation state zero is found in tetrairidium dodecacarbonyl, Ir4(CO)12, which is the most common and stable binary carbonyl of 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. 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]

  Isotopes

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-life of 73.827 days, 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] Isotopes with masses below 191 decay by some combination of β+ decay, α decay, and proton emission, with the exceptions of 189Ir, which decays by electron capture, and 190Ir, which decays by positron emission. Synthetic isotopes heavier than 191 decay by β decay, although 192Ir also has a minor electron capture decay path.[22] 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. 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 is 190m3Ir 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. This renders it useful for Mössbauer spectroscopy for research in physics, chemistry, biochemistry, metallurgy, and mineralogy.[25]

  History

The discovery of iridium is intertwined with that of platinum and the other metals of the platinum group. 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.[28] 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. 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]

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 πτηνος (ptènos) for winged.[30][31] 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[IrCl6nH2O) by a sequence of reactions with sodium hydroxide and hydrochloric acid.[31] He named iridium after Iris (Ιρις), 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]

Photo of part of a black vase with brown picture on it: A woman with wings on her back hold an arrow with right hand and gives a jar to a man. A small deer is standing in front of the woman.
  The Greek goddess Iris, after whom iridium was named.

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. 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 O2 and H2 for each kilogram of iridium.[4]

These extreme difficulties in melting the metal limited the possibilities for handling iridium. 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 Holland and William Lofland Dudley were able to melt iridium by adding phosphorus and patented the process in the United States; 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]

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] This phenomenon, known as the Mössbauer effect (which has since been observed for other nuclei, such as 57Fe), and developed as Mössbauer 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]

  Occurrence

A large black egg)shaped boulder of porous structure standing on its top, tilted.
  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; gold is 40 times more abundant, platinum is 10 times more abundant, and silver and mercury are 80 times more abundant.[3] Tellurium is about as abundant as iridium, and only three naturally occurring elements are less abundant: rhenium, ruthenium, and rhodium, iridium being 10 times more abundant than the last two.[3] 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]

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). 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: 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 in Russia, and the Sudbury Basin in Canada are also significant sources of iridium. 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 alluvial deposits. 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]

  Cretaceous–Paleogene boundary presence

A cliff with pronounced layered structure: yellow, gray, white, gray. A red arrow points between the yellow and gray layers.
  The red arrow points to the Cretaceous–Paleogene boundary.

The Cretaceous–Paleogene boundary of 65 million years ago, marking the temporal border between the Cretaceous and Paleogene periods of geological time, was identified by a thin stratum of iridium-rich clay.[41] 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] 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]

  Production

Year Price
($/ozt)[46][47][48]
2001 415.25
2002 294.62
2003 93.02
2004 185.33
2005 169.51
2006 349.45
2007 444.43
2008 448.34
2009 420.4
2010 635

Iridium is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper and 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.[46][49] 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 chlorine with hydrochloric acid.[18][40]

After it is dissolved, iridium is separated from the other platinum group metals by precipitating (NH4)2IrCl6 or by extracting IrCl2−
6
with organic amines.[50] The first method is similar to the procedure Tennant and Wollaston used for their separation. 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 metallurgy techniques.[51][52]

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. 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]

  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]

  Industrial and medical

Skeletal formula of a chemical compound with iridium atom in its center, bonded to 6 benzol rings. The rings are pairwise connected to each other.
  Molecular structure of Ir(mppy)3

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] 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] 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. For example, high-temperature crucibles made 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] 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]

The radioisotope iridium-192 is one of the two most important sources of energy for use in industrial γ-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. 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] 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. 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. 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 vacuum on a base layer of chromium.[67]

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 a conversion 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]

Skeletal formula presentation of a chemical transformation. The initial compounds have a C5H5 ring on their top and an iridium atom in the center, which is bonded to two hydrogen atoms and a P-PH3 group or to two C-O groups. Reaction with alkane under UV light alters those groups.
  Oxidative addition to hydrocarbons in organoiridium chemistry[69][70]

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]

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]

  Historical

Fountain pen tip made of yellowish metal
  Fountain pen nib labeled Iridium Point

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). 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. 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]

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; 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] 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] 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.[38]

  Notes

  1. ^ Most common oxidation states of iridium are in bold. The right column lists one representative compound for each oxidation state.
  2. ^ Iridium literally means "of rainbows".
  3. ^ Like other precious metals, iridium is customarily traded in troy ounces, which are equivalent to about 31.1 grams.
  4. ^ The definition of the meter was changed again in 1983. The meter is currently defined as the distance traveled by light in a vacuum during a time interval of 1299,792,458 of a second.

  References

  1. ^ J. W. Arblaster: Densities of Osmium and Iridium, in: Platinum Metals Review, 1989, 33, 1, S. 14–16; Volltext.
  2. ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
  3. ^ a b c d e f g h i j k l m n Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth–Heinemann. pp. 1113–1143, 1294. ISBN 0-7506-3365-4. OCLC 37499934 41901113 213025882 37499934 41901113. 
  4. ^ a b c d e f g h i j k l m n o Hunt, L. B. (1987). "A History of Iridium". Platinum Metals Review 31 (1): 32–41. http://www.platinummetalsreview.com/pdf/pmr-v31-i1-032-041.pdf. 
  5. ^ Kittel, C. (2004). Introduction to Solid state Physics, 7th Edition. Wiley-India. ISBN 81-265-1045-5. 
  6. ^ Arblaster, J. W. (1995). "Osmium, the Densest Metal Known". Platinum Metals Review 39 (4): 164. http://www.platinummetalsreview.com/dynamic/article/view/pmr-v39-i4-164-164. 
  7. ^ Cotton, Simon (1997). Chemistry of Precious Metals. Springer-Verlag New York, LLC. p. 78. ISBN 978-0-7514-0413-5. 
  8. ^ Lide, D. R. (1990). CRC Handbook of Chemistry and Physics (70th Edn.). Boca Raton (FL):CRC Press. 
  9. ^ Arblaster, J. W. (1989). "Densities of osmium and iridium: recalculations based upon a review of the latest crystallographic data" (PDF). Platinum Metals Review 33 (1): 14–16. http://www.platinummetalsreview.com/pdf/pmr-v33-i1-014-016.pdf. 
  10. ^ a b c d e f g h i j k l m n Emsley, J. (2003). "Iridium". Nature's Building Blocks: An A–Z Guide to the Elements. Oxford, England, UK: Oxford University Press. pp. 201–204. ISBN 0-19-850340-7. 
  11. ^ a b Perry, D. L. (1995). Handbook of Inorganic Compounds. CRC Press. pp. 203–204. ISBN [[Special:BookSources/0-8492-8671-3|0-8492-8671-3]]. 
  12. ^ Lagowski, J. J., ed. (2004). Chemistry Foundations and Applications. 2. Thomson Gale. pp. 250–251. ISBN [[Special:BookSources/0-02-865732-3|0-02-865732-3]]. 
  13. ^ Jung, D.; Demazeau, Gérard (1995). "High Oxygen Pressure and the Preparation of New Iridium (VI) Oxides with Perovskite Structure: Sr2MIrO6 (M = Ca, Mg)". Journal of Solid State Chemistry 115 (2): 447–455. Bibcode 1995JSSCh.115..447J. DOI:10.1006/jssc.1995.1158. 
  14. ^ Gong, Y.; Zhou, M.; Kaupp, M.; Riedel, S. (2009). "Formation and Characterization of the Iridium Tetroxide Molecule with Iridium in the Oxidation State +VIII". Angewandte Chemie International Edition 48: 7879–7883. DOI:10.1002/anie.200902733. 
  15. ^ Gulliver, D. J; Levason, W. (1982). "The chemistry of ruthenium, osmium, rhodium, iridium, palladium and platinum in the higher oxidation states". Coordination Chemistry Reviews 46: 1–127. DOI:10.1016/0010-8545(82)85001-7. 
  16. ^ Holleman, A. F.; Wiberg, E.; Wiberg, N. (2001). Inorganic Chemistry, 1st Edition. Academic Press. ISBN 0-12-352651-5. OCLC 47901436. 
  17. ^ Černý, R.; Joubert, J.-M.; Kohlmann, H.; Yvon, K. (2002). "Mg6Ir2H11, a new metal hydride containing saddle-like IrH5−
    4
    and square-pyramidal IrH4−
    5
    hydrido complexes". Journal of Alloys and Compounds 340 (1–2): 180–188. DOI:10.1016/S0925-8388(02)00050-6.
     
  18. ^ a b c d e Renner, H.; Schlamp, G.; Kleinwächter, I.; Drost, E.; Lüschow, H. M.; Tews, P.; Panster, P.; Diehl, M.; Lang, J.; Kreuzer, T.; Knödler, A.; Starz, K. A.; Dermann, K.; Rothaut, J.; Drieselman, R. (2002). "Platinum group metals and compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley. DOI:10.1002/14356007.a21_075. 
  19. ^ Vaska, L.; DiLuzio, J.W. (1961). "Carbonyl and Hydrido-Carbonyl Complexes of Iridium by Reaction with Alcohols. Hydrido Complexes by Reaction with Acid". Journal of the American Chemical Society 83 (12): 2784–2785. DOI:10.1021/ja01473a054. 
  20. ^ Crabtree, R. H. (1979). "Iridium compounds in catalysis". Accounts of Chemical Research 12 (9): 331–337. DOI:10.1021/ar50141a005. 
  21. ^ Crabtree, R. H. (2005). The Organometallic Chemistry of the Transition Metals. Wiley. ISBN 978-0-471-66256-3. OCLC 224478241. http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471662569.html. 
  22. ^ a b c d e Audi, G. (2003). "The NUBASE Evaluation of Nuclear and Decay Properties". Nuclear Physics A (Atomic Mass Data Center) 729: 3–128. Bibcode 2003NuPhA.729....3A. DOI:10.1016/j.nuclphysa.2003.11.001. 
  23. ^ a b c Mager Stellman, J. (1998). "Iridium". Encyclopaedia of Occupational Health and Safety. International Labour Organization. pp. 63.19. ISBN 978-92-2-109816-4. OCLC 45066560 35279504 45066560. http://books.google.com/?id=nDhpLa1rl44C&pg=PT125. 
  24. ^ Arblaster, J. W. (2003). "The discoverers of the iridium isotopes: the thirty-six known iridium isotopes found between 1934 and 2001". Platinum Metals Review 47 (4): 167–174. http://www.platinummetalsreview.com/dynamic/article/view/47-4-167-174. 
  25. ^ a b Chereminisoff, N. P. (1990). Handbook of Ceramics and Composites. CRC Press. p. 424. ISBN 0-8247-8006-X. 
  26. ^ Ogden, J. M. (1976). "The So-Called 'Platinum' Inclusions in Egyptian Goldwork". The Journal of Egyptian Archaeology 62: 138–144. DOI:10.2307/3856354. JSTOR 3856354. 
  27. ^ Chaston, J. C. (1980). "The Powder Metallurgy of Platinum". Platinum Metals Rev. 24 (21): 70–79. 
  28. ^ McDonald, M. (959). "The Platinum of New Granada: Mining and Metallurgy in the Spanish Colonial Empire". Platinum Metals Review 3 (4): 140–145. http://www.platinummetalsreview.com/dynamic/article/view/pmr-v3-i4-140-145. 
  29. ^ Juan, J.; de Ulloa, A. (1748) (in Spanish). Relación histórica del viage a la América Meridional. 1. p. 606. 
  30. ^ Thomson, T. (1831). A System of Chemistry of Inorganic Bodies. Baldwin & Cradock, London; and William Blackwood, Edinburgh. p. 693. 
  31. ^ a b Griffith, W. P. (2004). "Bicentenary of Four Platinum Group Metals. Part II: Osmium and iridium – events surrounding their discoveries". Platinum Metals Review 48 (4): 182–189. DOI:10.1595/147106704X4844. 
  32. ^ Weeks, M. E. (1968). Discovery of the Elements (7 ed.). Journal of Chemical Education. pp. 414–418. ISBN 0-8486-8579-2. OCLC 23991202. 
  33. ^ Tennant, S. (1804). "On Two Metals, Found in the Black Powder Remaining after the Solution of Platina". Philosophical Transactions of the Royal Society of London 94: 411–418. DOI:10.1098/rstl.1804.0018. JSTOR 107152. 
  34. ^ Trigg, G. L. (1995). Landmark Experiments in Twentieth Century Physics. Courier Dover Publications. pp. 179–190. ISBN 0-486-28526-X. OCLC 31409781. 
  35. ^ Mössbauer, R. L. (1958). "Gammastrahlung in Ir191" (in German). Zeitschrift für Physik A 151 (2): 124–143. Bibcode 1958ZPhy..151..124M. DOI:10.1007/BF01344210. 
  36. ^ Waller, I. (1964). "The Nobel Prize in Physics 1961: presentation speech". Nobel Lectures, Physics 1942–1962. Elsevier. http://nobelprize.org/nobel_prizes/physics/laureates/1961/press.html. 
  37. ^ Scott, E. R. D.; Wasson, J. T.; Buchwald, V. F. (1973). "The chemical classification of iron meteorites—VII. A reinvestigation of irons with Ge concentrations between 25 and 80 ppm". Geochimica et Cosmochimica Acta 37 (8): 1957–1983. Bibcode 1973GeCoA..37.1957S. DOI:10.1016/0016-7037(73)90151-8. 
  38. ^ a b "Iridium" (PDF). Human Health Fact Sheet. Argonne National Laboratory. 2005. http://www.ead.anl.gov/pub/doc/Iridium.pdf. Retrieved 2008-09-20. 
  39. ^ Xiao, Z.; Laplante, A. R. (2004). "Characterizing and recovering the platinum group minerals—a review". Minerals Engineering 17 (9–10): 961–979. DOI:10.1016/j.mineng.2004.04.001. 
  40. ^ a b c d Seymour, R. J.; O'Farrelly, J. I. (2001). "Platinum-group metals". Kirk Othmer Encyclopedia of Chemical Technology. Wiley. DOI:10.1002/0471238961.1612012019052513.a01.pub2. 
  41. ^ a b Alvarez, L. W.; Alvarez, W.; Asaro, F.; Michel, H. V. (1980). "Extraterrestrial cause for the Cretaceous–Tertiary extinction". Science 208 (4448): 1095–1108. Bibcode 1980Sci...208.1095A. DOI:10.1126/science.208.4448.1095. PMID 17783054. 
  42. ^ Hildebrand, A. R.; Penfield, Glen T.; Kring, David A.; Pilkington, Mark; Zanoguera, Antonio Camargo; Jacobsen, Stein B.; Boynton, William V. (1991). "Chicxulub Crater; a possible Cretaceous/Tertiary boundary impact crater on the Yucatan Peninsula, Mexico". Geology 19 (9): 867–871. Bibcode 1991Geo....19..867H. DOI:10.1130/0091-7613(1991)019<0867:CCAPCT>2.3.CO;2. http://geology.geoscienceworld.org/cgi/content/abstract/19/9/867. 
  43. ^ Frankel, C. (1999). The End of the Dinosaurs: Chicxulub Crater and Mass Extinctions. Cambridge University Press. ISBN 0-521-47447-7. OCLC 40298401. 
  44. ^ Ryder, G.; Fastovsky, D. E.; Gartner, S. (1996). The Cretaceous-Tertiary Event and Other Catastrophes in Earth History. Geological Society of America. p. 47. ISBN 0-8137-2307-8. 
  45. ^ Toutain, J.-P.; Meyer, G. (1989). "Iridium-Bearing Sublimates at a Hot-Spot Volcano (Piton De La Fournaise, Indian Ocean)". Geophysical Research Letters 16 (12): 1391–1394. Bibcode 1989GeoRL..16.1391T. DOI:10.1029/GL016i012p01391. 
  46. ^ a b c George, M. W. (2008). "Platinum-group metals" (PDF). U.S. Geological Survey Mineral Commodity Summaries (USGS Mineral Resources Program). http://minerals.usgs.gov/minerals/pubs/commodity/platinum/mcs-2008-plati.pdf. 
  47. ^ George, M. W. (2006). "Platinum-group metals" (PDF). U.S. Geological Survey Mineral Commodity Summaries (USGS Mineral Resources Program). http://minerals.usgs.gov/minerals/pubs/commodity/platinum/platimcs06.pdf. 
  48. ^ Platinum-group metals. U.S. Geological Survey Mineral Commodity Summaries (January 2011 )
  49. ^ George, M. W. (PDF). 2006 Minerals Yearbook: Platinum-Group Metals. United States Geological Survey USGS. http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2006-plati.pdf. 
  50. ^ Gilchrist, Raleigh (1943). "The Platinum Metals". Chemical Reviews 32 (3): 277–372. DOI:10.1021/cr60103a002. 
  51. ^ Ohriner, E. K. (2008). "Processing of Iridium and Iridium Alloys". Platinum Metals Review 52 (3): 186–197. DOI:10.1595/147106708X333827. 
  52. ^ Hunt, L. B.; Lever, F. M. (1969). "Platinum Metals: A Survey of Productive Resources to industrial Uses" (PDF). Platinum Metals Review 13 (4): 126–138. http://www.platinummetalsreview.com/pdf/pmr-v13-i4-126-138.pdf. 
  53. ^ Hagelüken, C. (2006). "Markets for the catalysts metals platinum, palladium, and rhodium" (PDF). Metall 60 (1–2): 31–42. http://www.preciousmetals.umicore.com/publications/articles_by_umicore/general/show_Metal_PGMmarkets_200602.pdf. 
  54. ^ Jollie, D. (2008) (PDF). Platinum 2008. Johnson Matthey. ISSN 0268-7305. http://www.platinum.matthey.com/uploaded_files/Pt2008/08_complete_publication.pdf. Retrieved 2008-10-13. 
  55. ^ Egorova, R. V.; Korotkov, B. V.; Yaroshchuk, E. G.; Mirkus, K. A.; Dorofeev N. A.; Serkov, A. T. (1979). "Spinnerets for viscose rayon cord yarn". Fibre Chemistry 10 (4): 377–378. DOI:10.1007/BF00543390. 
  56. ^ Darling, A. S. (1960). "Iridium Platinum Alloys" (PDF). Platinum Metals Review 4 (l): 18–26. http://www.platinummetalsreview.com/pdf/pmr-v4-i1-018-026.pdf. Retrieved 2008-10-13. 
  57. ^ Biggs, T.; Taylor, S. S.; van der Lingen, E. (2005). "The Hardening of Platinum Alloys for Potential Jewellery Application". Platinum Metals Review 49 (1): 2–15. DOI:10.1595/147106705X24409. 
  58. ^ Crookes, W. (1908). "On the Use of Iridium Crucibles in Chemical Operations". Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character 80 (541): 535–536. Bibcode 1908RSPSA..80..535C. DOI:10.1098/rspa.1908.0046. JSTOR 93031. 
  59. ^ a b Handley, J. R. (1986). "Increasing Applications for Iridium". Platinum Metals Review 30 (1): 12–13. http://www.platinummetalsreview.com/pdf/pmr-v30-i1-012-013.pdf. 
  60. ^ Stallforth, H.; Revell, P. A. (2000). Euromat 99. Wiley-VCH. ISBN 978-3-527-30124-9. http://books.google.com/?id=I03qepnj2IwC. 
  61. ^ Cheung, H.; Tanke, R. S.; Torrence, G. P. (2000). "Acetic acid". Ullmann's Encyclopedia of Industrial Chemistry. Wiley. DOI:10.1002/14356007.a01_045. 
  62. ^ Halmshaw, R. (1954). "The use and scope of Iridium 192 for the radiography of steel". British Journal of Applied Physics 5 (7): 238–243. Bibcode 1954BJAP....5..238H. DOI:10.1088/0508-3443/5/7/302. 
  63. ^ Hellier, Chuck (2001). Handbook of Nondestructive Evlaluation. The McGraw-Hill Companies. ISBN 978-0-07-028121-9. 
  64. ^ Penzes, W. B. (2001). "Time Line for the Definition of the Meter". National Institute for Standards and Technology. http://www.mel.nist.gov/div821/museum/timeline.htm. Retrieved 2008-09-16. 
  65. ^ General section citations: Recalibration of the U.S. National Prototype Kilogram, R. S. Davis, Journal of Research of the National Bureau of Standards, 90, No. 4, July–August 1985 (5.5 MB PDF, here); and The Kilogram and Measurements of Mass and Force, Z. J. Jabbour et al., J. Res. Natl. Inst. Stand. Technol. 106, 2001, 25–46 (3.5 MB PDF, here) 
  66. ^ Ziegler,, E.; Hignette, O.; Morawe, Ch.; Tucoulou, R. (2001). "High-efficiency tunable X-ray focusing optics using mirrors and laterally-graded multilayers". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 467–468: 954–957. Bibcode 2001NIMPA.467..954Z. DOI:10.1016/S0168-9002(01)00533-2. 
  67. ^ "Face-to-Face with Jerry Johnston, CXC Program Manager & Bob Hahn, Chief Engineer at Optical Coating Laboratories, Inc., Santa Rosa, CA". Harvard-Smithsonian Center for Astrophysics; Chandra X-ray Center. 1995. http://chandra.harvard.edu/press/bios/johnston.html. Retrieved 2008-09-24. 
  68. ^ Möhl, D. (1997). "Production of low-energy antiprotons". Zeitschrift Hyperfine Interactions 109: 33–41. Bibcode 1997HyInt.109...33M. DOI:10.1023/A:1012680728257. 
  69. ^ a b Janowicz, A. H.; Bergman, R. G. (1982). "Carbon-hydrogen activation in completely saturated hydrocarbons: direct observation of M + R-H -> M(R)(H)". Journal of the American Chemical Society 104 (1): 352–354. DOI:10.1021/ja00365a091. 
  70. ^ a b Hoyano, J. K.; Graham, W. A. G. (1982). "Oxidative addition of the carbon-hydrogen bonds of neopentane and cyclohexane to a photochemically generated iridium(I) complex". Journal of the American Chemical Society 104 (13): 3723–3725. DOI:10.1021/ja00377a032. 
  71. ^ Källström, K; Munslow, I; Andersson, P. G. (2006). "Ir-catalysed asymmetric hydrogenation: Ligands, substrates and mechanism". Chemistry – A European Journal 12 (12): 3194–3200. DOI:10.1002/chem.200500755. PMID 16304642. 
  72. ^ Roseblade, S. J.; Pfaltz, A. (2007). "Iridium-catalyzed asymmetric hydrogenation of olefins". Accounts of Chemical Research 40 (12): 1402–1411. DOI:10.1021/ar700113g. PMID 17672517. 
  73. ^ Wang, X.; Andersson, M. R.; Thompson, M. E.; Inganäsa, O. (2004). "Electrophosphorescence from substituted poly(thiophene) doped with iridium or platinum complex". Thin Solid Films 468 (1–2): 226–233. Bibcode 2004TSF...468..226W. DOI:10.1016/j.tsf.2004.05.095. 
  74. ^ Tonzetich, Zachary J. (2002). "Organic Light Emitting Diodes—Developing Chemicals to Light the Future" (PDF). Journal of Undergraduate Research (Rochester University) 1 (1). http://sa.rochester.edu/jur/issues/fall2002/tonzetich.pdf. Retrieved 2008-10-10. 
  75. ^ Holder, E.; Langefeld, B. M. W.; Schubert, U. S. (2005-04-25). "New Trends in the Use of Transition Metal-Ligand Complexes for Applications in Electroluminescent Devices". Advanced Materials 17 (9): 1109–1121. DOI:10.1002/adma.200400284. 
  76. ^ Mottishaw, J. (1999). "Notes from the Nib Works—Where's the Iridium?". The PENnant XIII (2). http://www.nibs.com/ArticleIndex.html. 
  77. ^ Crookes, W., ed. (1867). "The Paris Exhibition". The Chemical News and Journal of Physical Science XV: 182. 
  78. ^ Pepper, J. H. (1861). The Playbook of Metals: Including Personal Narratives of Visits to Coal, Lead, Copper, and Tin Mines, with a Large Number of Interesting Experiments Relating to Alchemy and the Chemistry of the Fifty Metallic Elements. Routledge, Warne, and Routledge. p. 455. 
  79. ^ "Radioisotope Brief: Iridium-192 (Ir-192)" (PDF). Radiation Emergencies. Centers for Disease Control and Prevention. 2004-08-18. http://emergency.cdc.gov/radiation/isotopes/pdf/iridium.pdf. Retrieved 2008-09-20. 

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