Iridium, radioactive. Iridium metal: history, properties, how it is obtained and where it is used

Iridium

IRIDIUM-I; m.[from Greek. iris (iridos) - rainbow] A chemical element (Ir), a heavy, refractory, grayish-white rare earth metal (used for protective coatings). Iridium mining.

◁ Iridium, th, th. I. alloy. I. pen tip.

(lat. Iridium), chemical element Group VIII of the periodic system, refers to the platinum metals. Density 22.65 g / cm 3, t pl 2447°C. Used for applying protective coatings. Component of alloys with Pt, Os, etc. (chemical equipment, standards of measures, parts of measuring instruments, soldering of "eternal feathers"). The name is from the Greek iris, rainbow.

IRIDIUM (lat. Iridium, from the Greek "iris" - rainbow), Ir (read "iridium"), a chemical element with atomic number 77, atomic mass 192.22. Consists of a mixture of two stable isotopes 193 Ir (62.7% by weight) and 191 Ir (37.3%). It is located in the VIIIB group, in the 6th period of the Periodic Table of the Elements. Part of the osmium triad (cm. OSMIUM)-iridium-platinum, (cm. PLATINUM) is a platinum metal. Configuration of the outer and pre-outer electron shells 5 s 2 p 6 d 7 6s 2 . Oxidation states from +1 to +6 (valencies I-VI). The most characteristic oxidation states are +3 and +4.
The radius of the atom is 0.135 nm, the ionic radius of the Ir 2+ ion is 0.089 nm, the Ir 3+ ion is 0.082 nm, Ir 4+ is 0.077 nm, Ir 5+ is 0.071 nm. Sequential ionization energies 9.1 and 17.0 eV. Electronegativity according to Pauling (cm. PAULING Linus) 2,2.
Iridium is a heavy, silvery-white metal.
Discovery history
Discovered in 1804 by the English chemist S. Tennant (cm. TENNANT Smithson) who studied the composition of platinum minerals.
Being in nature
Iridium is a very rare element, the content in the earth's crust is 1 10 -7% by weight. Occurs in nature in the form of alloys with osmium (osmium iridium), platinum, rhodium (cm. RHODIUM), ruthenium (cm. RUTHENIUM) and other platinum metals (cm. PLATINUM METALS). In a dispersed form (10–4% by mass) it is found in sulfide copper-nickel iron-bearing ores.
Receipt
The main source of iridium is anode sludge from copper-nickel production. The resulting sludge is enriched. Then, acting on him with aqua regia (cm. AQUA REGIA), when heated, platinum, palladium are transferred into a solution (cm. PALLADIUM (chemical element)), rhodium, iridium and ruthenium in the form of chloride complexes H 2 , H 2 , H 3 , H 2 and H 2 . Osmium remains in an insoluble precipitate. From the resulting solution, by adding ammonium chloride NH 4 Cl, the platinum complex (NH 4) 2 is first precipitated, and then the complex of iridium (NH 4) 2 and ruthenium (NH 4) 2 is precipitated. When calcined (NH 4) 2 in air, metallic iridium is obtained:
(NH 4) 2 \u003d Ir + N 2 + 6HCl + H 2.
Physical and Chemical properties
Iridium is a heavy silver-white metal (density at 20 ° C 22.65 kg / dm 3). The cubic lattice is face-centered, a= 0.38387 nm. Melting point 2447 °C, boiling point 4380 °C. In the series of standard potentials, it is located to the right of hydrogen (cm. HYDROGEN). Iridium is stable in air, does not react with non-oxidizing acids and water.
Differs in high chemical firmness. It interacts with non-metals only in a finely divided state at a temperature of red heat. Interaction with oxygen (cm. OXYGEN) occurs only at temperatures above 1000 ° C, with the formation of iridium dioxide IrO 2.
Iridium oxides do not dissolve in water, acids and alkalis.
Compact iridium at temperatures up to 100 °C does not react with all known acids and their mixtures, including aqua regia. To convert these metals into water-soluble chloro complexes, the powder containing these metals is chlorinated by heating in the presence of NaCl complexing agent:
Ir + 2Cl 2 + 2NaCl \u003d Na 2
Hydroxide Ir(OH) 4 (IrO 2 2H 2 O) is formed by neutralization of solutions of chloroiridates(IV) in the presence of oxidizing agents. Precipitate Ir 2 O 3 x H 2 O precipitates upon neutralization of chloroiridates (III) with alkali and is easily oxidized in air to IrO 2 . Iridium hydroxides are practically insoluble in water. Iridium oxides are converted into a soluble form by oxidizing them in the presence of a complexing agent:
IrO 2 + 4HCl + 2NaCl \u003d Na 2 + 2H 2 O.
The highest oxidation state +6 is manifested in iridium in the hexafluoride IrF 6 . It is a very strong oxidizing agent capable of oxidizing even water:
2IrF 6 + 10H 2 O \u003d 2Ir (OH) 4 + 12HF + O 2,
or NO:
NO + IrF 6 \u003d NO + -.
As for others d-elements, iridium is characterized by the formation of complex compounds with a coordination number of 6. A large number of organoiridium compounds with an Ir-C bond are known.
Application
Pure iridium is used to make crucibles for growing single crystals, foil for non-amalgamating cathodes, and critical parts of instrumentation. Iridium is used for iridating product surfaces. The radioactive isotope 192 Ir is used as a portable source of g-radiation for radiographic studies of pipelines and radiotherapy oncological diseases. Until 1960, a bar made of platinum-iridium alloy, located at the International Bureau of Weights and Measures in Sevres, served as the international standard of the meter. On one of the planes of this beam, two strokes are applied, at a distance of 1 m from each other.

encyclopedic Dictionary. 2009 .

See what "iridium" is in other dictionaries:

- (from Greek iris rainbow). Metal, from the platinum group, the compounds of which are distinguished by iridescent colors. Dictionary foreign words included in the Russian language. Chudinov A.N., 1910. IRIDIUM noble metal gray color; beats weight 22.5. It's melting... ... Dictionary of foreign words of the Russian language

M l, Ir. cube. White. Tv. 7. Beat in. 22.6. Observed only at microscopic studies as decay products in Pt. Possibly contains Pt and is close to platinum Ir. Not studied. Geological dictionary: in 2 volumes. M.: Nedra. Under… … Geological Encyclopedia

IRIDIUM, irid husband. a very hard, whitish metal, usually found in an alloy with osmium and together with platinum. Iridium, iridium, relating to the metal iridium. Iridium, containing an admixture of iridium. Dictionary Dahl. IN AND. Dal. 1863 1866 ... Dahl's Explanatory Dictionary

- (Iridium), Ir, chemical element of group VIII of the periodic system, atomic number 77, atomic mass 192.22; refers to platinum metals. Discovered by the English chemist S. Tennant in 1804 ... Modern Encyclopedia

Iridium is a chemical element with atomic number 77 in periodic system, denoted by the symbol Ir (lat. Iridium).

In 1804, the English chemist Smithson Tennant, examining the black powder remaining after the dissolution of native platinum in aqua regia, discovered two new elements in it. The salts of one of them were literally painted in all the colors of the rainbow. Tennant didn't have to rack his brains for a long time in search of a suitable name for it: the element was named iridium, since in Greek "irioeides" - iridescent.
The destinies of platinum metals are intertwined so closely that a story about one of them is unthinkable without mentioning the others. In 1840, professor of Kazan University K. K. Klaus became interested in the problems of processing the Ural platinum ore. At his request, the St. Petersburg Mint sent him samples of platinum residues - an insoluble precipitate formed after processing raw platinum with aqua regia. "At the very beginning of work," the scientist later wrote, "I was surprised at the wealth of my residue, for I extracted from it, in addition to 10% platinum, a considerable amount of iridium, rhodium, osmium, several palladium and a mixture of various metals of special content ..."
If at first Klaus set himself only a purely practical goal - to find a way to process the remains of platinum ore into platinum, then soon these studies acquired a deeper scientific character and completely captured the scientist. “For two full years,” Klaus recalled, “I groaned over it from early morning until late at night, living only in the laboratory, having dinner and drinking tea there, and in doing so I became a terrible empiricist.” The last statement had a very specific meaning: according to A. M. Butlerov -
student Klaus, he "had a habit ... when dissolving platinum ores in aqua regia, stir the liquid directly with all five fingers and determined the strength of unreacted acids by taste." However, this was characteristic not only of Klaus, but also of other chemists of the old school, who, having received any substance, always “tasted” it (until the middle of the 19th century, when describing the properties of a substance, it was necessary to indicate its taste), exposing themselves to great danger. : so, the famous Swedish scientist Karl Scheele died after tasting the anhydrous hydrocyanic acid he received. Klaus's work was crowned with success: a method for processing platinum residues was found, and now the scientist had to go to St. Petersburg to report this to the Minister of Finance E.F. Kankrin, who was interested in a successful solution to the problem. For a trip to the capital, Klaus was forced to borrow 90 rubles from one of his friends (the scientist was able to repay the debt only a few years later, when he gained worldwide fame). Upon arrival in St. Petersburg, Klaus was received by the minister two days later and obtained permission from him to obtain the materials necessary to continue research. He was given 1/2 pound of platinum residues and 1/4 pound of raw platinum. Returning to Kazan, the scientist again plunged headlong into the work, which lasted for many years and gave excellent results. The most important of them was the discovery in 1844 of a previously unknown chemical element - the last "Russian member of the platinum family". “Already at the first work,” Klaus wrote, “I noticed the presence of a new body, but at first I did not find a way to separate it from impurities. I worked on this subject for more than a year, but finally discovered an easy and the right way obtaining it in its purest state. This new metal, which I named ruthenium in honor of our fatherland (from the Latin name for Russia - S.V.), belongs without
doubts about very curious bodies."
But Klaus's discovery was not immediately recognized. The scientist sent the first samples of compounds of the new element to Stockholm J.Ya. Berzelius, who enjoyed great prestige among all chemists. What was the disappointment of Klaus when he learned that, according to this venerable scientist, the substance sent to him did not contain a new element, but was a poorly purified iridium compound. Convinced of his innocence, Klaus conducted experiments again and again, sometimes forgetting about elementary protective measures. True, a few years later, the scientist warned his colleagues: “When working with osmium iridium, one must beware of osmic acid vapors. This is a very volatile
the substance belongs to the most harmful bodies and acts mainly on the lungs and eyes, producing strong inflammations. I suffered a lot from her." Too great was Klaus's desire to convince scientific world in that a new element was actually discovered, and he finally managed to do it. Preparations of ruthenium compounds were again sent to Berzelius, and he, after careful research, realized that he had previously been mistaken in his conclusions. "Please accept my sincere congratulations on your excellent discoveries and their elegant processing," he wrote to Klaus, "thanks to them, your name will be indelibly inscribed in the history of chemistry."
The result of Klaus's hard work was the work "Chemical study of the remains of the Ural platinum ore and ruthenium metal" published in 1845, in which for the first time the properties of iridium were also comprehensively described, and Klaus himself noted that he dealt with iridium more than other metals of the platinum group. The scientist's recommendations became the scientific basis for creating a technology for producing iridium and other platinoids.

Finding iridium in nature

The content of iridium in the earth's crust is negligible (10 −7 mass %). It is much rarer than gold and platinum and, together with rhodium, rhenium and ruthenium, is one of the least common elements. However, iridium is relatively common in meteorites and it is possible that the actual content of the metal on the planet is much higher: its high density and high affinity for iron (siderophilicity) could lead to the displacement of iridium deep into the Earth, into the core of the planet, in the process of its formation from the melt.

Physical propertiesiridium

A heavy, silvery-white metal that is difficult to machine due to its hardness.
The cubic lattice is face-centered, a 0=0.38387 nm
Electrical resistance - 5.3 10 −8 Ohm m (at 0 °C)
Linear expansion coefficient - 6.5 × 10 −6 degrees
Modulus of normal elasticity - 52.029 × 10 6 kg / mm²

Chemical propertiesiridium

The most important compounds with the metal iridium

Iridium (III) hydroxide Ir (OH) 3, more precisely hydrated iridium (III) oxide Ir 2 O 3 *nH 2 O green precipitate, obtained by precipitation from a solution of sodium chloroiridate (III) Na 3 . Iridium(III) compounds are reducing agents, Ir(OH) 3 is oxidized by oxygen to Ir(OH) 4 . Ir 2 O 3 disproportionates into Ir and IrO 2 when heated.
Iridium(IV) oxide. IrO 2 is obtained as a blue-black powder by decomposition of the hydroxide or oxidation of iridium. resistor material.
Iridium hydroxide (IV) Ir (OH) 4. Dark blue amorphous substance, insoluble in water, solutions of acids and alkalis, except for concentrated sulfuric acid. Obtained by alkaline hydrolysis (NH 4) 2 .
Halides. The product of direct interaction of iridium with fluorine is iridium hexafluoride IrF 6 . This compound is very active, it not only reacts with water according to the equation
IrF 6 + 5H 2 O \u003d Ir (OH) 4 + 6HF + 1 / 2O 2,
but even oxidizes chlorine, and IrF 4 and ClF are formed. Used for coating.
Iridium(III) and (IV) chlorides, crystals, are hydrolyzed by water. The formation of complex chlorides upon interaction with alkali metal chlorides is characteristic: Na 3 - green crystals, Na 2 - dark red, soluble, potassium and ammonium hexachloroiridates (IV) - slightly soluble.
Iridium salts. In general, iridium forms few common salts. Salts of iridium(III) with complex cations are similar to the corresponding salts of chromium (III) and cobalt(III), they are strong complex compounds X 3 , X 3 , X 2 .
Iridium carbonyls: yellow-green Ir 2 (CO) 8, sublimes, and bright yellow Ir 4 (CO) 12, decomposes when heated. Used for coating.

In addition to iridium-192, which you already know, there are 14 more radioactive isotopes of this element with mass numbers from 182 to 198. The heaviest isotope has the shortest life: its half-life is less than a minute. Curiously, the half-life of iridium-183 is exactly one hour. The element has only two stable isotopes - iridium-191 and iridium-193. The share of the more "weighty" of them in the natural mixture accounts for approximately 62% of the atoms.

The iridium isotope is associated with the discovery of the so-called Mssbauer effect, on which amazingly accurate methods for measuring small quantities and weak phenomena are based, which are widely used in physics, chemistry, biology, and geology. This effect (or, to put it strictly scientifically, resonant nuclear absorption of gamma rays in solids without recoil) was discovered by a young physicist from Germany, Rudolf Mssbauer, in 1958. A few years earlier, when his studies at the Technische Hochschule in Munich were coming to an end, he began to look for a topic for thesis. One of the professors kindly offered the student a long list of topics. As Mssbauer himself recalls, he did not like any of them, except for the last one (by the way, the thirteenth in a row), the main advantage of which, according to the future physicist, was that he had not the slightest idea about it. It was about resonant absorption of gamma quanta by atomic nuclei. "The most important thing," recalls the physicist, "was that they poked me in the nose into this matter." And "this thing" went smoothly. First, the diploma was defended, two years later the turn of the dissertation came, and a year later the opening took place. Working in Heidelberg, at the Max Planck Institute for Medical Research, the scientist continued to work on resonant absorption. With a special counter, he determined the number of gamma quanta that had passed through metallic iridium, more precisely, through one of its isotopes; the sources of these gamma quanta were excited atomic nuclei of the same isotope. Nuclei in the normal state can also be "excited", but for this they must, having absorbed a gamma quantum, receive such an amount of energy that exactly corresponds to the difference between the energies of the nucleus in the excited and ground states (this absorption is called resonant). Usually, however, the energy of gamma quanta turns out to be slightly less than necessary, since part of it is lost when the emitting nucleus recoils (something similar happens, for example, when a cannon or gun is fired).

To eliminate some side processes that could distort the results of the experiments, Mssbauer decided to cool the iridium to the temperature of liquid nitrogen. At the same time, he believed that due to a decrease in the speed of the nuclei, the resonant absorption would decrease, and the number of gamma quanta passing through iridium would increase accordingly (other physicists were of the same opinion). To the surprise of the experimenter, everything turned out to be the opposite. What is the reason? The scientist concludes: in solids at a sufficiently low temperature, the recoil is perceived not by a separate nucleus, but by the whole substance, and therefore the energy loss for recoil is vanishingly small, i.e., the energy of a gamma quantum is exactly

is equal to the difference between the energies of the nucleus in the excited and ground states. This discovery was recognized as one of the most important scientific events of our time (in 1961, Mssbauer was awarded the Nobel Prize). Today, the Mssbauer effect has already been discovered on several dozen elements, but the history of science has forever linked the discovery of this most important physical phenomenon with the hero of our story - iridium.

Receiptiridium

The main source of iridium production is anode sludge from copper-nickel production. Au, Pd, Pt, etc. are separated from the concentrate of platinum group metals. The residue containing Ru, Os and Ir is alloyed with KNO 3 and KOH, the alloy is leached with water, the solution is oxidized with Cl 2, OsO 4 and RuO 4 are distilled off, and the precipitate containing iridium is fused with Na 2 O 2 and NaOH, the alloy is treated with aqua regia and a solution of NH 4 Cl, precipitating iridium in the form of (NH 4) 2, which is then calcined to obtain metallic Ir. A promising method is the extraction of iridium from solutions by extraction of hexachloroiridates with higher aliphatic amines. For the separation of iridium from base metals, the use of ion exchange is promising. To extract iridium from minerals of the osmic iridium group, the minerals are alloyed with BaO 2 , treated with hydrochloric acid and aqua regia, OsO 4 is distilled off and iridium is precipitated in the form of (NH 4) 2 .

In our time, pure iridium is isolated from native osmiridium and from the remains of platinum ores, but before that, using various reagents, platinum, osmium, palladium and ruthenium are extracted from them, and only after that comes the turn of iridium. The resulting powder is either pressed into semi-finished products and alloyed or remelted in electric furnaces in an argon atmosphere. At ordinary temperatures, iridium is brittle and cannot be processed in any way, but when hot, it is more "compliant" and allows itself to be forged.

Applicationiridium

Alloys with W and Th - materials for thermoelectric generators, with Hf - materials for fuel tanks in spacecraft, with Rh, Re, W - materials for thermocouples operated above 2000 °C, with La and Ce - materials for thermionic cathodes.

Iridium is also used to make pen nibs. A small ball of iridium can be found on the tips of pens and ink refills, it is especially visible on gold nibs, where it differs in color from the nib itself.

Iridium is a metal and a chemical element. The element is in the periodic table under the atomic number 77. It is considered a native of noble rocks, solid, has a white-gold color.

The mineral exists in pure form, but the first mention of an isotopic metal is associated with the fall of an iron-nickel meteorite to Earth. The collision with the Earth of a meteorite occurred 65 million years ago, in the era of Triceraptors and Dipladocians. In the Earth, the fallen object left a trail, the consequences of which are still visible today. A crater 180 kilometers deep was formed, the dust that rose due to the violation of the earth's crust and the fall of a meteorite made the Earth remain in darkness for 14 days, volcanic eruptions occurred in Asia, Hindustan and Madagascar.

Some scientists suggest that it was this metal that killed all dinosaurs and other large dinosaurs, due to the fact that it began to release a toxin when it came into contact with chlorine and the earth's core. As you know, the metal melts at 2300 degrees Celsius.

So, he lay in the Earth for all 65 million years, until he was accidentally discovered by people who were looking for platinum and found it at the site of an old crater.

As an earth element, iridium was discovered in 1804 by the scientist S. Tennat. As a result of the procedures for the study of platinum minerals and the detection of osmium in them, iridium was discovered.

This is how the Yucatan disaster led to the fact that in periodic table Iridium appeared.

Origin of the metal

Iridium is a platanoid, which is a product of multiphase nuclear synthesis of elements. On the planet, among other metals (out of 1005), it occupies only a 3% value, which means its infrequent detection. Scientists believe that iridium is hidden in the earth's core or in a molten nickel-iron layer (outer core).

It occurs in the earth's crust as an alloy with osmium or platinum.

How to receive

We have already said that this metal is found only in alloys. But how is it possible to obtain iridium?
The source of the rock is the anode sludge of copper-nickel production. The product - sludge is saturated, after which, under the action of "aqua regia", it is transferred from a solid to a liquid state, in the form of H2 chloride compounds.

As a result, chemists obtain a liquid mixture of metals and add ammonium chloride NH4Cl to it. After that, the precipitate is removed from platinum, and then an iridium complex (NH4) 2 is obtained. (NH4)2 is calcined with oxygen and nitrogen. The output is metallic iridium.

Mining sites

The chemical element is found in alloy form in folded terrestrial rocks of the mountains of Russia, peretonite rocks located in South Africa, Kenya, South America etc.

Where there is platinum, there is also iridium.

On the characteristics of metal as a chemical element:

The element is found in different colors, the most common is white - KIrF6, lemon - IrF5, gold - K3IrCl6, light green - Na3IrBr6, pink - Cs3IrI6, crimson - Na2IrBr6, dark blue - IrI3. The variety of colors is due to the presence of various salts in iridium.

By the way, the metal got its name due to this variety of colors. Irida is the goddess of the rainbow in Greek mythology.

Properties and features

Where applicable

Basically, not iridium itself is used, but its alloys with metals.

An alloy of iridium and platinum is used to make dishes, to conduct chemical experiments, to create surgical equipment, jewelry and insoluble anodes. Another copper-iridium mixture is used for the instrument structure. This alloy is particularly durable, it is used to cover welding units in construction projects.

Iridium is also mixed with hafnium, in which case the alloy will serve as a tool for creating fuel tanks.

When an isotopic metal is mixed with tungsten, rhodium, or rhenium, thermocouples are made from the resulting substance. Thermocouples are devices for measuring temperatures above 2000 degrees.

Iridium, together with cerium, lathanum, is used in the production of cathodes.

And here is one iridium, without auxiliary elements, used to make fountain pen nibs.

Iridium is used on a large industrial scale to create iridium spark plugs. Such candles will last 3 years longer than conventional ones and will withstand a car mileage of 160 thousand kilometers more than standard ones.

Due to iridium, the structure of flaw detectors has been facilitated, which reveal all the shortcomings of manual start mechanisms.

In addition to applications in medicine and industry, a chemical element is taken as the basis for many chemical operations. It is a thermal, chemical catalyst to accelerate the production of the final chemical product. For example, it is often used to produce nitric acid.

Due to iridium, crystals are grown in heat-resistant crucibles, which are necessary for laser technology. Thanks to scientists and this gift of nature, an operation for laser vision correction, laser crushing of kidney stones, etc., became possible.

The scope of the metal is large, but its cost is quite high, so iridium is often replaced with synthetic chemical elements, which are inferior to the natural counterpart in everything.

It is irreplaceable, which is necessary for the functioning of machines, construction sites, the creation of durable mechanisms and other things.

Pure iridium is used to make crucibles for laboratory purposes and mouthpieces for blowing refractory glass. You can, of course, use it as a cover. However, there are difficulties here. It is difficult to apply to another metal by the usual electrolytic method, and the coating is quite loose. The best electrolyte would be complex iridium hexachloride, but it is unstable in aqueous solution, and even in this case the quality of the coating leaves much to be desired.

A method has been developed for producing iridium coatings electrolytically from molten potassium and sodium cyanides at 600°C. In this case, a dense coating up to 0.08 mm thick is formed.

It is less laborious to obtain iridium coatings by cladding. A thin layer of metal-coating is laid on the base metal, and then this “sandwich” goes under a hot press. In this way, iridium-coated tungsten and molybdenum wires are obtained. A billet of molybdenum or tungsten is inserted into an iridium tube and forged in a hot state, and then drawn to the desired thickness at 500-600 ° C. This wire is used to make control grids in electron tubes.

Iridium coatings can also be applied to ceramics by chemical means. For this, they receive iridium complex salt solution, for example with phenol or some other organic matter. Such a solution is applied to the surface of the product, which is then heated to 350-400 ° C in a controlled atmosphere, i.e. in atmosphere with controlled redox potential. Under these conditions, organic matter evaporates or burns out, and the iridium layer remains on the product.

But coatings are not the main application of iridium. This metal improves mechanical and physiochemical properties other metals. It is usually used to increase their strength and hardness. The addition of 10% iridium to relatively soft platinum almost triples its hardness and tensile strength. If the amount of iridium in the alloy is increased to 30%, the hardness of the alloy will not increase much, but the tensile strength will double again - up to 99 kg / mm 2. Since these have exceptional corrosion resistance, they are used to make heat-resistant crucibles that can withstand strong heat in aggressive environments. In such crucibles, in particular, crystals for laser technology are grown. Platinum-iridium alloys also attract jewelers - jewelry made from these alloys is beautiful and hardly wears out. Standards are also made from a platinum-iridium alloy, sometimes a surgical instrument.

AT In the future, iridium with platinum may acquire particular importance in the so-called low-current technology as an ideal material for contacts. Every time a closure occurs and opening of a conventional copper contact, a spark occurs; as a result, the copper surface oxidizes rather quickly. AT contactors for strong currents, for example, for electric motors, this phenomenon does not really harm the work: the contact surface is cleaned from time to time with sandpaper, and the contactor is again ready for operation. But, when we are dealing with low-current equipment, for example, in communications technology, a thin layer of copper oxide has a very strong effect on the entire system, making it difficult for current to pass through the contact. Namely, in these devices, the switching frequency is especially large - it is enough to recall automatic telephone exchanges (automatic telephone exchanges). This is where non-burning platinum-iridium contacts come to the rescue - they may work almost forever! The only pity is that these alloys are very expensive and until they are not enough.

Add not only to platinum. Small additions of element No. 77 to tungsten and molybdenum increase the strength of these metals at high temperatures. A meager addition of iridium to titanium (0.1%) dramatically increases its already significant resistance to acids. the same applies to chrome. Thermocouples made of iridium and iridium-rhodium alloy (40% rhodium) operate reliably at high temperature in an oxidizing atmosphere. An alloy of iridium and osmium is used to make soldering points for fountain pen nibs and compass needles.

Summarizing, we can say that metallic iridium is used mainly because of its constancy - the dimensions of metal products, its physical and chemical properties are constant, and, so to speak, are constant at the highest level.

Like other Group VIII, iridium can be used in chemical industry as a catalyst. Iridium-nickel catalysts are sometimes used to produce propylene from acetylene and methane. Iridium was part of the platinum catalysts for the formation of nitrogen oxides (in the process of obtaining nitric acid). One of the oxides of iridium, IrO 2 , was tried to be used in the porcelain industry as a black paint. But this paint is too expensive ...

The reserves of iridium on Earth are small, its content in the earth's crust is calculated in millionths of a percent. The production of this element is also small - no more than a ton per year. Worldwide!

In this regard, it is difficult to assume that over time, dramatic changes will come in the fate of iridium - it will forever remain a rare and expensive metal. But where it is used, it serves flawlessly, and this unique reliability is a guarantee that science and industry of the future will not do without iridium.

IRIDIUM WATCHMAN. In many chemical and metallurgical industries, for example in domain, it is very important to know the level solid materials in aggregates. Usually for this controls use bulky probes suspended on special probe winches. AT last years probes began to be replaced small containers with artificial radioactive isotope - iridium -192. 192 Ir nuclei emit high-energy gamma rays

energy; the half-life of the isotope is 74.4 days, part of the gamma rays is absorbed by the mixture, and radiation detectors record the weakening of the flux. The latter is proportional to the distance,

which the rays pass in the mixture. Iridium-192 is also successfully used to control welds; with its help, all uncooked places and foreign inclusions are clearly recorded on the film. Gamma flaw detectors with iridium-192 are also used to control the quality of products made of steel and aluminum alloys.

Mössbauer effect. In 1958, young German physicist Rudolf

Mössbauer made a discovery that attracted the attention of all physicists in the world. The effect discovered by Mössbauer made it possible to measure very weak nuclear phenomena with amazing accuracy. Three years after the discovery, in 1961, Mössbauer received for his work Nobel Prize. For the first time this effect was discovered on the nuclei of the iridium-192 isotope.

BEATS HARDER. One of the most interesting changes platinum-iridium alloys in recent years - the manufacture of electrical stimulators of cardiac activity from them. AT a patient with angina pectoris is implanted with electrodes with platinum-iridium clamps. The electrodes are connected to a receiver, which is also in the patient's body. The generator with a ring antenna is located outside, for example, in the patient's pocket. The ring antenna is mounted on the body opposite the receiver. When the patient feels that an angina attack is coming, he turns on the generator. The ring antenna receives pulses that are transmitted to the receiver, and from it to the platinum-iridium electrodes. The electrodes, by transmitting impulses to the nerves, make them beat more actively.

STABLE AND UNSTABLE. In previous notes, quite a lot was said about the radioisotope iridium-192, which is used in numerous devices and even involved in an important scientific discovery. But, in addition to iridium-192, this element has 14 more radioactive isotopes with mass numbers from 182 to 198. The heaviest isotope at the same time is the shortest-lived one, its half-life is less than a minute. The isotope iridium-183 is interesting only because its half-life is exactly one hour. Iridium has only two stable isotopes. On theshare heavier - iridium-193 in the natural mixture accounts for 62,7%. The share of light iridium-191, respectively, is 37.3%.

The German precious metals trading company Degussa Goldhandel GmbH has begun offering iridium and ruthenium bars to private investors for the first time. The offer of these precious metals as an investment product is a new step in the market.
In addition to traditional precious metals such as gold, silver, platinum, palladium and rhodium, investors will now be able to buy investment bars of iridium and ruthenium with a purity of 999/1000 and a mass of 1 ounce (31.1 grams).

The production of iridium and ruthenium is a complex metallurgical process. Basically, these precious metals are used in industry. Also wide application they are found in medical technology, mechanical engineering and the chemical industry. For industrial customers, Degussa offers iridium and ruthenium in powder form.

Cost of 1 ingot iridium on February 23, 2018 is € 1200, ruthenium - € 372, rhodium - € 1975.

More about iridium

Iridium in paleontology and geology is an indicator of the layer that formed immediately after the fall of meteorites, which is no coincidence - iridium is relatively common in meteorites and is considered a space metal.

Even before the discovery of the Chisculub crater, many scientists drew attention to a large number of iridium in deposits dating back to the extinction of the last dinosaurs. This convinced paleontologists that the asteroid was responsible for the extinction of these giant lizards. These sediment layers contain great amount carbon in the form of soot.

It is assumed that the Chisculub crater was formed as a result of an asteroid impact with a diameter of about 10 km. The impact energy is estimated at 5 1023 joules or 100 teraton in TNT equivalent (for comparison, the largest thermonuclear device had a power of the order of 0.00005 teraton, which is 2 million times less.

A small amount of iridium has been found in the solar photosphere.

Iridium(ancient Greek ἶρις - rainbow) got its name thanks to various colors their salts
- a refractory metal belonging to the platinum group. Iridium has a silvery white color and is a refractory and hard metal. The density of iridium, along with the density of osmium, is the highest among all metals. The metal has high anti-corrosion properties at ultra-high temperatures up to 2000 C.

Iridium belongs to the group most expensive metals and in its value is second only to rhodium, platinum and gold. In nature, the metal is found together with ruthenium, rhenium and rhodium. The metal is one of the components of such minerals as aurosmiride, sysertskite and nevyanskite.

iridium mining

Industrial enterprises extract iridium from sludge generated during copper-nickel production. The extraction of iridium takes place in several stages: obtaining a concentrate, leaching of crude metal, purification from impurities. When separating iridium from metals that are not noble, the ion exchange method can be used. When extracting metal from minerals, the mining process goes through the stage of fusion with barium oxide, treatment with aqua regia and hydrochloric acid solution. As a result, when separating osmium, a complex compound is obtained, which must be calcined in order to obtain pure iridium.

An alloy of iridium with platinum makes it possible to obtain a material with high strength characteristics, this alloy is not subject to oxidation. From this alloy, in particular, kilogram standard.

Russian enterprises producing iridium:

— JSC "Krastsvetmet";
- NPP "Billon";
— OJSC MMC Norilsk Nickel.

Application of iridium

• • In the electrical and electrochemical sectors. For chemically and thermally resistant dishes, and a catalyst that accelerates reactions, in particular the production of nitric acid. In bowls made of an alloy of platinum and iridium, gold is dissolved with a mixture of acids called "royal" vodka.
  • As a source of electricity the nuclear isomer of iridium, iridium-192m2, is used. As a component of alloys, the metal is used for the manufacture of thermoelectric generators, thermocouples, thermionic cathodes and fuel tanks. Iridium-192 is a radionuclide with a half-life of 74 days, widely used in flaw detection, especially in conditions where generating sources cannot be used (explosive environments, lack of supply voltage of the required power).
  • In medicine. From iridium get high-strength protective covering for ceramics and metals. The addition of iridium improves the strength properties and hardness of other metals. The metal is used for the production of high-strength surgical instruments.
  • For the manufacture of crucibles. The metal is used as the main material in which high-purity single crystals are subsequently grown. Iridium crucibles are also used for melting high quality glass.
  • For making pen nibs. A small ball of iridium can be found on the tips of pens and ink refills, it is especially visible on gold nibs, where it differs in color from the nib itself.
  • In spark plugs as a material for the manufacture of electrodes, making such candles the most durable (100-160 thousand km of car run) and reducing the requirements for sparking voltage. Initially used in aviation and racing cars, then, as the cost of production fell, it began to be used on mass cars. Currently, such plugs are available for most engines, but are the most expensive.
  • In jewelry iridium has only recently been used. In Russia, in 1999, rings were made from it, followed by gold items decorated with iridium inlay. A favorite material for jewelers is an iridium-platinum alloy. The addition of 10% of this super-hard substance improves the strength of platinum by three times, and the products become incomparable beauty. appearance and impeccable strength.

The first set in the history of numismatics with an iridium coin

The iridium coin was included in the Rwandan coin set. The set includes five coins, the denomination of each is 10 Rwandan francs. The coins have the same diameter of 11 mm. Each coin from precious metal packed in organic glass.
On the front side coins depict the coat of arms of Rwanda, on the reverse - the head of a lion and specifications coins: the metal from which each coin is minted and the year of issue "2013".

Coin made of 999 gold (proof), its weight is 1/100 oz.
Silver coin 999 (proof), coin weight 1/25 oz.
Coin made of iridium 999 (BU), its weight is 1/25 oz.
Coin made of palladium 999 proof (proof), the weight of such a coin is 1/100 oz.
Coin made of 999 platinum (proof), its weight is 1/100 oz.

Circulation of the set - 1000 pcs.