On Tuesday, Venezuelan authorities admitted that they had lost a capsule containing the radioactive substance iridium-192. The capsule was stolen on Sunday - unknown armed criminals took the truck carrying the substance from the driver. The alpha particles released by iridium-192 are very dangerous radioactive compounds for the human body. Its half-life is at least 70 years.

The first to admit the theft of a car in which a capsule with highly radioactive material was transported was the head of the Venezuelan Civil Defense Department, Colonel Antonio Rivero. True, the military man expressed confidence that the thieves’ target was a truck, not a capsule. “It’s unlikely that they knew about this most dangerous cargo,” the American television company CNN quotes him as saying.

But nevertheless, Antonio Rivero admitted in an interview with Reuters that “the situation is an emergency - all the forces of the police and military have been sent to search for the capsule.”

According to Rivero, we are talking about the substance iridium-192, used for X-ray machines in medicine. The incident occurred last Sunday evening in the state of Yaracuy. A group of armed people stopped the car, took the driver and those accompanying the cargo out of it, and then fled in this car.

Speaking on local television, the director of the atomic energy department of the Venezuelan Ministry of Energy, Angel Diaz, called on the attackers “not to touch the capsule and return it immediately,” the EFE agency reports.

Angel Diaz also asked the attackers to "immediately return the potentially lethal device." Unlike Colonel Rivero, who called the incident “a simple theft of a truck,” Diaz said that he “cannot rule out the use of the capsule for malicious purposes.”

He once again warned the thieves that careless handling of the radioactive substance could have “very serious consequences for them and ordinary residents, even death is not excluded.”

The device contains iridium-192, which emits powerful gamma radiation and is used for industrial X-rays, such as to detect faults in underground industrial pipes.

By the way, this is not the first time that iridium-192 has gone missing in Venezuela. In March, two capsules containing iridium-192 were also stolen due to the carelessness of security guards. However, later the authorities returned the dangerous cargo back.

The worst incident in Latin America involving the theft of radioactive materials occurred in Brazil in 1987. Scavengers discovered a container of cesium-137. It appears to have been accidentally dumped from a hospital where the dangerous substance was also used in X-ray equipment. Not knowing that the material was radioactive, they opened the capsule.

Later, children began playing with the dangerous substance - as CNN reports, they "smeared the material on their faces and bodies because they liked the way it warmed their bodies." As a result, five people died and 249 suffered from radiation poisoning.

Pure iridium is used to make crucibles for laboratory purposes and mouthpieces for blowing refractory glass. You can, of course, also use it as a coating. However, there are difficulties here. The usual electrolytic method is difficult to apply to another metal, and the coating turns out to be 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 labor-intensive to obtain iridium coatings using the cladding method. A thin layer of coating metal is laid on the base metal, and then this “sandwich” is put under a hot press. In this way, tungsten and molybdenum wires with iridium coating are obtained. A workpiece made of molybdenum or tungsten is inserted into an iridium tube and hot forged, and then drawn to the desired thickness at 500-600 ° C. This wire is used to make control grids in electronic tubes.

It is possible to apply iridium coatings to ceramics using a chemical method. To do this they get a solution of a complex iridium salt, for example with phenol or some other organic substance. 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. V atmosphere with controlled redox potential. Under these conditions, organic matter evaporates or burns out, and a layer of iridium remains on the product.

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

IN In the future, iridium and platinum may acquire particular importance in so-called low-current technology as an ideal material for contacts. Every time there is a short circuit And opening of a conventional copper contact causes a spark; As a result, the copper surface oxidizes quite quickly. IN In contactors for high currents, for example for electric motors, this phenomenon does not greatly harm the operation: the surface of the contacts is cleaned with sandpaper from time to time, 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 and makes it difficult for current to pass through the contact. Namely, in these devices the frequency of switching on is especially high - just remember automatic telephone exchanges (ATS). This is where non-burning platinum-iridium contacts come to the rescue - they can work almost forever! It's just a pity that these alloys are very expensive and There aren't enough of them yet.

They 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 tiny addition of iridium to titanium (0.1%) dramatically increases its already significant resistance to acids. The same applies to chromium. Thermocouples composed of iridium and iridium-rhodium alloy (40% rhodium) operate reliably at high temperatures in an oxidizing atmosphere. An alloy of iridium and osmium is used to make soldering tips for fountain pen nibs and compass needles.

To summarize, 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, constant at the highest level.

Like other Group VIIIs, iridium can be used in the chemical industry as a catalyst. Iridium-nickel catalysts are sometimes used to produce propylene from acetylene and methane. Iridium was part of platinum catalysts for the reaction of the formation of nitrogen oxides (in the process of producing nitric acid). One of the iridium oxides, 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 imagine that dramatic changes will occur in the fate of iridium over time - it will forever remain a rare and expensive metal. But where it is used, it serves reliably, and this unique reliability is the guarantee that science and industry of the future will not do without iridium.

IRIDIUM GUARDIAN. In many chemical and metallurgical industries, for example in domain, it is very important to know the level solid materials in units. Usually for this control uses bulky probes suspended on special probe winches. IN In recent years, probes have begun to be replaced small containers with artificial radioactive isotope - iridium -192. 192 Ir nuclei emit high gamma rays

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

which the rays pass through the charge. Iridium-192 is also successfully used to control welds; with its help, all uncooked areas and foreign inclusions are clearly recorded on photographic film. Gamma flaw detectors with iridium-192 are also used for quality control 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 the Nobel Prize for his work. This effect was first discovered on nuclei of the isotope iridium-192.

BEATS MORE ACTIVELY. One of the most interesting changes platinum-iridium alloys in recent years - the manufacture of electrical cardiac stimulators from them. IN In a patient with angina pectoris, electrodes with platinum-iridium clamps are implanted. The electrodes are connected to a receiver, which is also located 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-iridis electrodes. Electrodes, 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 is even involved in an important scientific discovery. But, besides 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, 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. Onshare heavier - iridium-193 in the natural mixture accounts for 62,7%. The share of light iridium-191 is 37.3%.

IRIDIUM, radioactive (Iridium; Ir), - chemical element of group VIII of the periodic system of elements of D. I. Mendeleev, serial number 77, atomic weight 192.2; belongs to the platinum metals. Silver-white metal, density 22.5 g/cm 3, temperature pl 2443°, resistant to chemicals. influences. In connections ch. arr. tri- and tetravalent.

I. has two stable isotopes with mass numbers 191 (38.5%) and 193 (61.5%), as well as 24 radioactive (including 5 isomers) with mass numbers from 182 to 198. Most radioisotopes of I. are short- and ultra-short-lived , four have half-lives of 1.7 to 11.9 days, an isotope with a mass number of 192-74.2 days. Of all the radioisotopes, only 192 Ir has found practical application: in technology - for gamma flaw detection and in medicine - for radiation therapy.

192 Ir is obtained by irradiating a natural iron target with neutrons in a nuclear reactor using the reaction (n, gamma), which occurs with a high yield (δ = 700 barn). In this case, along with 192 Ir, 194 Ir is also formed, which, however, after exposure of the irradiated target for several days, decays, turning into the stable isotope 194 Pt (see Isotopes).

I. is used in medicine for interstitial and intracavitary radiation therapy (see) in the form of iridium needles and wires coated with a thin layer (0.1 mm) of platinum to absorb 192 Ir beta radiation. Iridium wire with 192 Ir is usually used using the afterloading technique: it is placed in hollow nylon tubes previously inserted into the patient. In wedge. In practice, iridium wire is used, creating an exposure dose rate of 0.5-1.5 mR/hour at a distance of 1 hour (per 1 cm of wire length), i.e., with a linear activity of 1-3 μCurie/cm.

Isotopes, including 192 Ir, belong to group B in terms of radiotoxicity, i.e., in the workplace, open drugs with an activity of up to 10 microcuries can be used in the workplace without permission from the sanitary-epidemiological service.

Bibliography: Levin V.I. Obtaining radioactive isotopes. M., 1972; Paine S. N. Modern after-loading methods for interstitial radiotherapy, Clin. Radiol., v. 23, p. 263, 1972, bibliogr.

V.V. Bochkarev.

Iridium is a metal and chemical element. The element is listed in the periodic table under atomic number 77. It is considered to come from noble rocks, is hard, and has a white-golden color.

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

Some scientists suggest that it was this metal that killed all dinosaurs and other large lizards, 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, metal melts at 2300 degrees Celsius.

So, it lay in the Earth for all 65 million years, until it was discovered by chance by people looking for platinum and finding it on the site of an old crater.

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

This is how the Yucatan disaster led to the appearance of Iridium in the periodic table.

Origin of the metal

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

In the earth's crust it occurs as an alloy with osmium or platinum.

How do you get it?

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 anode sludge from copper-nickel production. The product - sludge is saturated, after which, under the influence of “regia vodka”, 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 this, the sediment is removed from the platinum, and then an iridium complex (NH4)2 is obtained. (NH4)2 is calcined with oxygen and nitrogen. The output is metallic iridium.

Mining locations

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

Where there is platinum, there is also iridium.

About the characteristics of metal as a chemical element:

Characteristic	Designation, meaning
Iridium is represented by the symbol	Ir
Number in the periodic table	77
Atomic weight	192.22 amu
Oxidation states	From 1 to 6 (5 not included)
Density at room temperature	22.7 g/cm^3
Density in liquid state	19.39 g/cm^3
Melting	At 2300 degrees Celsius
Boiling of liquid iridium	At 45 degrees Celsius
Has a crystal lattice	Face-centered cube

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. Iris is the goddess of the rainbow in Greek mythology.

Properties and Features

Where is it used?

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

An alloy of iridium and platinum is used to make dishes, conduct chemical experiments, create surgical equipment, jewelry and insoluble anodes. A copper-iridium mixture is also used for the instrumentation structure. This alloy is particularly strong and is used to coat welding assemblies 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 instruments for measuring temperatures above 2000 degrees.

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

But iridium alone, without auxiliary elements, is used to create nibs for fountain pens.

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

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

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

Using iridium, crystals that are necessary for laser technology are grown in heat-resistant crucibles. Thanks to scientists and this gift of nature, surgery for laser vision correction, laser crushing of kidney stones, etc. has become possible.

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

This is an irreplaceable noble metal that is necessary for the functioning of machines, construction projects, the creation of durable mechanisms, and more.

Iridium (from the Greek iris rainbow) is a chemical element with atomic number 77 in the periodic table, designated by the symbol Ir (Latin Iridium). It is a very hard, refractory, silvery-white transition precious metal of the platinum group. Its density, along with the density of osmium, is the highest among all metals (the densities of Os and Ir are almost equal). Together with other members of the platinum family, iridium is a noble metal.

In 1804, while studying the black precipitate left after dissolving native platinum in aqua regia, the English chemist S. Tennant found two new elements in it. He called one of them osmium, and the second - iridium. Salts of the second element turned different colors under different conditions. This property was the basis for its name.

Iridium is a very rare element, its content in the earth’s crust is 10–7% by mass. It is found much less frequently than gold and platinum and, together with rhodium, rhenium and ruthenium, is one of the least common elements. In nature, it is found mainly in the form of osmic iridium, a frequent companion of native platinum. There is no native iridium in nature.

Whole iridium is non-toxic, but some of its compounds, such as IrF6, are very poisonous. It does not play any biological role in living nature.

PHYSICAL PROPERTIES OF IRIDIUM

Due to its hardness, iridium is difficult to machine.
Hardness on the Mohs scale – 6.5.
Density 22.42 g/cm3.
Melting point 2739 K (2466 °C).
Boiling point 4701 K (4428 °C).
Specific heat capacity 0.133 J/(K mol).
Thermal conductivity 147 W/(m K).
Electrical resistance 5.3 10-8 Ohm m (at 0 °C).
Linear expansion coefficient 6.5x10-6 degrees.
Modulus of normal elasticity 52.029x10-6 kg/mm2.
The heat of fusion is 27.61 kJ/mol.
The heat of evaporation is 604 kJ/mol.
Molar volume 8.54 cm3/mol.
The structure of the crystal lattice is face-centered cubic.
Lattice period 3.840 A.

Natural iridium occurs as a mixture of two stable isotopes: 191Ir (content 37.3%) and 193Ir (62.7%). Radioactive isotopes of iridium with mass numbers 164 - 199, as well as many nuclear isomers, have been obtained by artificial methods. The heaviest isotope is at the same time the shortest-lived, its half-life is less than a minute. The isotope iridium-183 is interesting only because its half-life is exactly one hour. The radioisotope iridium-192 is widely used in numerous devices.

CHEMICAL PROPERTIES OF IRIDIUM

Iridium has high chemical resistance. Stable in air, does not react with water. At temperatures up to 100 °C, compact iridium does not react with all known acids and their mixtures, including aqua regia.
It interacts with F2 at 400 - 450 °C, and with Cl2 and S at red heat. Chlorine forms four chlorides with iridium: IrCl, IrCl2, IrCl3 and IrCl4. Iridium trichloride is most easily obtained from iridium powder placed in a stream of chlorine at 600°C.
Iridium powder can be dissolved by chlorination in the presence of alkali metal chlorides at 600 - 900 °C:
Ir + 2Cl2 + 2NaCl = Na2.
Interaction with oxygen occurs only at temperatures above 1000°C, resulting in the formation of iridium dioxide IrO2, which is practically insoluble in water. It is converted into a soluble form by oxidizing in the presence of a complexing agent:
IrO2 + 4HCl + 2NaCl = Na2 + 2H2O.
The highest oxidation state of +6 occurs for iridium in the hexafluoride IrF6, the only halogen compound in which iridium is hexavalent. This is a very strong oxidizing agent that can oxidize even water:
2IrF6 + 10H2O = 2Ir(OH)4 + 12HF + O2.
Like all platinum group metals, iridium forms complex salts. Among them there are also salts with complex cations, for example Cl3, and salts with complex anions, for example K3 3H2O.

Deposits and production

In nature, iridium occurs in the form of alloys with osmium, platinum, rhodium, ruthenium and other platinum metals. It is found in dispersed form (10–4% by weight) in sulfide copper-nickel iron ores. The metal is one of the components of such minerals as aurosmiride, sysertskite and nevyanskite.

Primary deposits of osmic iridium are located mainly in peridotite serpentinites of folded regions (South Africa, Canada, Russia, USA, New Guinea). The annual production of iridium is about 10 tons.

Obtaining iridium

The main source of iridium is anode sludge from copper-nickel production. The resulting sludge is enriched and, by treating it with aqua regia while heating, platinum, palladium, rhodium, iridium and ruthenium are transferred into solution in the form of chloride complexes H2, H2, H3, H2 and H2. Osmium remains in an insoluble precipitate.
From the resulting solution, by adding ammonium chloride NH4Cl, a platinum complex (NH4)2 is first precipitated, and then a complex of iridium (NH4)2 and ruthenium (NH4)2.
When (NH4)2 is calcined in air, metallic iridium is obtained:
(NH4)2 = Ir + N2 + 6HCl + H2.
The powder is pressed into semi-finished products and melted or melted in electric furnaces in an argon atmosphere.

Russian iridium producing enterprises:
- JSC Krastsvetmet;
- NPP "Billon";
- OJSC MMC Norilsk Nickel.

APPLICATIONS OF IRIDIUM

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).

Iridium-192 is successfully used to control welds: with its help, all uncooked areas and foreign inclusions are clearly recorded on photographic film.
Gamma flaw detectors with iridium-192 are also used for quality control of products made of steel and aluminum alloys.

In blast furnace production, small containers with the same isotope of iridium are used to control the level of materials in the furnace. Since part of the emitted gamma rays is absorbed by the charge, by the degree of attenuation of the flux one can quite accurately determine how far the rays had to “make their way” through the charge, i.e., determine its level.

Of particular interest as a source of electricity is its nuclear isomer, iridium-192m2 (having a half-life of 241 years).

Iridium in paleontology and geology is an indicator of the layer that formed immediately after the fall of meteorites.

Small additions of element No. 77 to tungsten and molybdenum increase the strength of these metals at high temperatures.
A tiny addition of iridium to titanium (0.1%) dramatically increases its already significant resistance to acids.
The same applies to chromium.
Alloys with W and Th - materials of 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 of thermionic cathodes.

An alloy of iridium and osmium is used to make soldering tips for fountain pen nibs and compass needles.

To measure high temperatures (2000-23000 °C), a thermocouple is designed, the electrodes of which are made of iridium and its alloy with ruthenium or rhodium. So far, such a thermocouple is used only for scientific purposes, but the same barrier stands in the way of its introduction into industry - high cost.

Iridium, along with copper and platinum, is used in spark plugs of internal combustion engines as a material for the manufacture of electrodes, making such plugs the most durable (100 - 160 thousand km of vehicle mileage) and reducing the requirements for sparking voltage.

Heat-resistant crucibles are made from pure iridium, which can safely withstand high heat in aggressive environments; In such crucibles, in particular, single crystals of precious stones and laser materials are grown.

One of the most interesting applications of platinum-iridium alloys is the manufacture of electrical cardiac stimulators. Electrodes with platinum-iridium clamps are implanted into the heart of a patient with angina pectoris. The electrodes are connected to a receiver, which is also located 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. Electrodes, transmitting impulses to the nerves, make the heart beat more actively.

Iridium is used to coat product surfaces. 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.

Iridium can be used in the chemical industry as a catalyst. Iridium-nickel catalysts are sometimes used to produce propylene from acetylene and methane. Iridium was part of platinum catalysts for the reaction of the formation of nitrogen oxides (in the process of producing nitric acid).

Mouthpieces for blowing refractory glass are also made from iridium.

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. In particular, the kilogram standard is made from this alloy.

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

Where iridium is used, it serves reliably, and this unique reliability is the guarantee that science and industry of the future will not be able to do without this element.