Isotope of iridium 192. Iridium, radioactive. Physical properties of iridium

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 to occur; 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 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 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 the automatic telephone exchange (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%.

An iron-nickel meteorite, which contained a lot of iridium and others, and therefore was extremely massive, crashed into the Earth, hitting the edge of the Yucatan Peninsula (Mexico) 65 million years ago - during the era of the unchallenged reign of dinosaurs.

The soil from the crater with a diameter of 180 and a depth of 20 kilometers partly evaporated (along with most of the iridium), and partly dispersed. Dusty dusk set in. The shock wave that passed both through and around the planet initiated large-scale eruptions in Asia and on the territory of Hindustan, which at that time was sailing from Madagascar to the north and had not yet even crossed the equator. Smoke and dust of volcanic origin aggravated the situation even more...

Iridium – a marker of cosmic catastrophe

Some scientists hypothesize that dinosaurs were killed by the abundance of heavy metals in the air suspension. However, the most advanced biologists are inclined to consider the confluence of two factors fatal: the colossal size of animals and... the sneezing reflex. A sharp increase in blood pressure during spontaneous clearing of the airways is detrimental to the blood vessels - especially if you have to sneeze incessantly.

The disappearance of dinosaurs gave the opportunity for the development of mammals, the result of which was the emergence of humans. Grateful to heavenly intercession, man conducted research on meteorite remains from the largest craters. The iridium content in the debris of metal guests from space turned out to be record-breaking. The content of iridium in the sedimentary rocks that covered the earth shortly after the Yucatan disaster is equally record-breaking.

However, most of the noble metal, geologists are sure, is hidden in the bowels of the Earth.

Origin and properties of iridium

Like all platinoids, iridium is a product of multi-stage nuclear fusion of elements, possible during supernova explosions or in cataclysms of an even larger scale. Little iridium is formed, but the Earth is lucky to form in an area rich in metals. The concentration of iridium (as well as platinum) in the core of the planet seems natural (albeit unconfirmed).

The remains of iridium in the earth's crust are insignificant (40 times more gold), but they allow the extraction of several tons of the precious metal annually. The honor of discovering and naming iridium belongs to the Englishman Smithson Tennant. Admired by the variety of colors of the metal salts (milky white KIrF6, lemon yellow IrF5, yellow K3IrCl6, green Na3IrBr6, burgundy Cs3IrI6, crimson Na2IrBr6, black IrI3), the scientist proposed giving the new element the name of Iris, the Greek goddess of the rainbow.

Iridium is unyielding in processing. It took thirty years to obtain metal purified from impurities. As it turned out, pure iridium is malleable at bright glow temperatures. As it cools, it loses its ability to withstand mechanical stress and crumbles under load. Iridium powder, sealed in glass vessels, is a product of the work of refining enterprises.

For a long time, iridium was considered the champion in terms of density. Already today, theoretical calculations have brought osmium to first place - however, the difference is so small that it cannot be confirmed by simple weighing. And separating osmium from iridium is not an easy task!

Iridium and osmium are brothers forever

In nature, iridium and osmium are often combined. The natural mixture of metals may be called osmiridium - if there is more osmium - or iridiosmium, if the percentage of iridium in the alloy is higher. In domestic mineralogical practice, the names osmiride and osmium iridide have been established.

According to legends, in the first half of the 20th century, ground crystals of natural osmiride were soldered to the tips of golden nibs of “eternal” pens to ensure soft writing. In fact, such experiments are rare, but in mass reality, gold fountain pen nibs are strengthened with tungsten.

Among jewelry lovers, there is a small but stable and completely unsatisfied demand for products made from natural osmiride. Fans of exotic jewelry sometimes ask about the possibility of making osmiridium products.

Unfortunately, this mineral is extremely rare and not very decorative - although it is characterized by a strong metallic luster. Osmiride is hard, brittle and almost impossible to machine. In addition, the natural mixture of iridium and osmium often contains a considerable amount of impurities - platinum, gold - which changes both the appearance and cost of the material.

Artificially produced alloys of iridium and osmium are strictly standardized according to the percentage composition of elements, but they are expensive, in demand in industry and low-tech in terms of jewelry.

Applications of iridium

After the indispensability of iridium for the production of premium quality spark plugs was discovered, the automotive industry became the main consumer of the noble metal. Ups and downs in the production of passenger cars and iridium spark plugs for them cause differences in prices for refined metal. In one year, the world's automakers can increase the demand for iridium from one ton to almost eleven - so that next year, due to the crisis decline in sales, they can make do with half a ton of the precious platinum.

The need for iridium is constant among manufacturers of equipment operating in extreme conditions. Jet engines require iridium alloys because of their high temperature strength. Heat-resistant iridium alloy is an element of power plants of space robots powered by nuclear energy. Titanium alloyed with iridium serves in pipelines capable of operating in the deep ocean.

Radioactive iridium 192 is the main tool for quality control of welds. The same source of gamma radiation helps doctors defeat tumor processes.

A layer of iridium several atoms thick covers the mirrors of telescopes that receive X-rays. In the past, platinum-iridium plating was used to extend the life of artillery locks.

In the jewelry industry, iridium is used for decoration and inlays, although recent attempts have been made to produce iridium jewelry. Iridification of jewelry platinum is much more traditional: a ten percent addition of iridium makes the product durable, wear-resistant, and beautiful.

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.

The chemical symbol for iridium is Ir.

The atomic number of iridium is 77.

Atomic weight – 192.22 a. eat.

Oxidation states: 6, 4, 3, 2, 1, 0, - 1.

The density of iridium (at a temperature of 20 degrees) is 22.65 g/cm3.

The density of liquid iridium (at a temperature of 2443 degrees) is 19.39 g/cm3.

The melting point of iridium is 2466 degrees.

The boiling point of iridium is 44.28 degrees.

The structural crystal lattice of iridium is face-centered cubic.

The chemical element - iridium, brought from South America in 1803, was discovered in nature by the English chemist S. Tennant.

Iridium got its name from the Greek word - rainbow, since the salts of this metal have a variety of colors.

Iridium is a simple chemical element, a transitional precious metal of the platinum group, silvery-white in color, hard and refractory.

Iridium has a high density, like osmium. Theoretically, iridium and have the same density, where the difference is a slight error.

Iridium, even at a temperature of 2000 degrees, has high corrosion resistance.

Iridium is extremely rare in the earth's crust. Its content in nature is even lower than that of platinum. Iridium is found together with rhenium, and . Iridium is often found in meteorites. Today, the exact content of iridium in nature is still not known. It is possible that there is much more iridium in nature than expected. It is assumed that iridium, having a high density and affinity for iron, as a result of the formation of the planet earth, was able to move deep into the earth, into the core of the planet.

Iridium is a very heavy and hard noble metal. The high mechanical strength of iridium makes this metal difficult to machine. Radioactive isotopes of iridium were obtained artificially. In nature, iridium is presented as a mixture of two stable isotopes: iridium - 191 (37.3 percent) and iridium - 193 (62.7 percent).

Iridium is mainly obtained from anode sludge formed during the electrolysis of copper and nickel.

Iridium is a highly inert precious metal.

Iridium does not oxidize in air or when exposed to high temperatures. However, when iridium powder is calcined at a temperature of 600 to 1000 degrees, in a flow of oxygen, this metal forms iridium oxide (IrO2) in a small amount, and at a temperature of 1200 degrees, it partially evaporates in the form of iridium oxide (IrO3).

In compact form, iridium at temperatures up to 100 degrees does not interact with acids and their mixtures (for example, with aqua regia).

Iridium in the form of iridium black (freshly precipitated), partially dissolves in aqua regia (a mixture of hydrochloric and nitric acids) and forms a mixture of two iridium compounds: Ir(3) and Ir(4).

Iridium powder at a temperature of 600 - 900 degrees is dissolved by chlorination in the presence of alkali metal chlorides or sintering with oxides: Na2O2 and BaO2, followed by dissolution in acids.

Iridium reacts at red heat with chlorine and sulfur.

Iridium interacts at a temperature of 400 - 450 degrees with fluorine.

Nuclear isomer iridium – 192 m2, with a half-life of 241 years, used as a source of electricity.

Iridium is mainly used in the form of alloys. The most common of them is an alloy of iridium and platinum. Iridium alloys are used in the manufacture of chemical glassware, surgical instruments, insoluble anodes, jewelry, and this alloy also finds its application in precision instrument making.

Iridium alloyed with thorium and tungsten is used as a material for thermoelectric generators.

An alloy of iridium and hafnium is a material for fuel tanks used in spacecraft.

Iridium in an alloy with tungsten, rhodium and rhenium is used to make thermocouples that measure temperatures over 2000 degrees.

Iridium alloyed with cerium and lanthanum is used as a material for thermionic cathodes.

Iridium is used to make pen nibs, where the metal is especially visible on gold nibs.

Iridium, along with platinum and copper, is used as a component metal to prepare the alloy. Expensive electrodes are made from this alloy, which are found in spark plugs of internal combustion engines. An alloy of iridium, platinum and copper increases the service life of these electrodes, for a period of 100 - 160 thousand kilometers.

Iridium with platinum is a very durable and non-oxidizing alloy. Thanks to its strength and resistance to oxidation, it was even used to make the standard kilogram.

Iridium does not play a biological role as a trace element. Iridium is a non-toxic metal, although iridium compounds such as iridium hexafluoride (IrF6) have toxic properties.