Osmium: the most expensive and heaviest metal.

Not gold and not platinum are the most expensive metals from the table of D. I. Mendeleev, but osmium metal. This is the rarest and most expensive metal of silver-white color with a gray tint of blue tint. Among chemists, this metal is considered noble, belonging to the platinum group.

Consists of several isotopes. They are very difficult to separate, which is reflected in the cost. The most popular isotope is Osmium-187.

It is assumed that 0.5% of the mass of the earth's crust consists of osmium, and it is located in the core. The proportion between size and weight is amazing. A kilogram of compound is comparable in size to the average size chicken egg. A container with a volume of 0.5 liters filled with osmium powder weighs more than 15 kg. But the desire to cast dumbbells from such a convenient, in terms of size / weight ratio, material immediately disappears not only because of the price of the powder, for some this is not a problem, but because of its extreme rarity and inaccessibility.

Find ingots in forests, mountains, reservoirs will not work. So far, not a single nugget has been found. It is mined in ore deposits in the composition with iridium, platinum, in platinum-palladium ore, in copper and nickel ores. But the content of osmium in it is 0.001%. It is also found in meteorites. True, isotopes are separated from them in more than 9 months. Therefore, industrial production using osmium cost secondary raw materials which is not much cheaper.

The total production of the heaviest metal per year around the world is several tens of kilograms. But the extraction of platinum is increasing, where osmium is present and is extracted along the way. The figures are already 200 kg per year. So, the task is not so much to look for osmium, but to find more cheap way separating him from his neighbors.

The Norilsk Mining and Metallurgical Combine has achieved some success in this task. Received pure metal from copper-nickel ores. Its quantity on the planet is 0.000005% of the total mass rocks. But in Russia there is. And in Kazakhstan. And the main reserves are located in Tasmania, America, Australia. The largest are concentrated in South Africa. She dictates the prices.

History of discovery and natural properties

In 1803-1804 in England, when conducting experiments on platinum with aqua regia (a mixture of nitric acid and hydrochloric acid), in the resulting unknown precipitate, after the dissolution of platinum, a sharp, unpleasant odor resembling chlorine appeared. Thanks to this smell, the newly discovered metal got its name. True, on Greek. From the Greek "osmium" is translated as "smell".

Formally, this is because it is part of the platinum group. This is where true nobility ends. The properties of this metal, both chemical and physical, are still not fully understood. physical characteristics more or less clarified a few years ago.

Osmium

Price

The high cost is caused by the limited quantity. Since it is scarce in nature, and production is expensive, the market reacts accordingly. When compared with gold, it will be thousands of tons of gold against several tens of kilograms of production. Hence the price - it starts at 15 thousand and goes up to 200 thousand dollars per gram. On the world market, gold is 7.5 times cheaper.

Such figures indicate the unpopularity of the material for widespread use. The main role in the use of this heavy metal in alloys is played by strength. Products become incredibly wear-resistant by adding very small portions of metal to the composition.

Application

In wide industrial production osmium is rarely used because of its high cost. But where the effect can exceed material costs, it is, of course, used. As a raw material, it acts, most often, in powder. The metal itself is brittle and crumbles easily. Getting the powder is easy.

More use cases:

Not all osmium compounds are applicable to use. But scientists are working on it.

Danger and safety

Like other heavy metals, osmium does not have the most favorable effect on living organisms, not bypassing the human one. Any compounds with osmium are amazing internal organs cause loss of vision. Poisoning by vapors of the element leads to death. When observing animals, a sharp development of anemia was observed, and the lungs ceased to function. It is believed that this is a rapidly developing edema.

What is Osmium Tetroxide OsO4? And this is the very substance thanks to which the element bears its name. Extremely aggressive. Its scent cannot be ignored. There is no more terrible and disgusting smell in nature. In case of poisoning, the skin is also affected. The dermis turns green, turns black, and may even become dead. Blisters and ulcers may appear. It stays on for a very long time.

The danger of poisoning threatens, first of all, workers of industrial premises at the slightest concentration of vapors in the air. about any acceptable standards scientists no longer stutter. Therefore, the provided special clothing, respirators are a common occurrence in industries using osmium oxide. Everything is sealed, the containers are sealed and stored in accordance with already tested rules.

If, nevertheless, for some unthinkable reason, the osmium compound gets into the eyes, they must be washed for a long time, 20 minutes. Clean running water. And immediately to the doctor. When ingested through Airways osmium vapor is neutralized with sodium bicarbonate. It is available in aerosol packaging. Lots of milk inside. And gastric lavage.

The undoubted benefits of the heaviest metal

According to British scientists, this heavy metal blocks the development of cancer cells. Methods for the treatment of cancer using osmium, although very slowly, are already being developed.

In medicine, in pacing, it is used in implants, the manufacture of which requires precious metals to prevent the development of allergies. The composition of the implant, which replaces the elements of the heart, includes 10% osmium and 90% platinum. Of course, such devices are priced accordingly. The same proportion is used for the manufacture of pulmonary valves.

The use of osmium compounds for medical needs is noticeable in the production of especially durable, long-term use tools, such as scalpels, all kinds of metal-ceramic cutters. And you need quite a bit of raw materials for this, and the effect is amazing.

Microscopic additions of osmium to steel cutting grades allow you to create the sharpest blades.

Products, the use of which involves the use of the heaviest metal, are unsurpassed in wear resistance.

Commercial interest

The various amazing properties of osmium metal cause undoubted interest and genuine surprise. But these same properties kill commercial interest on the spot. And, in spite of everything, the price in the market does not fall.

If, from the point of view of practice, element No. 76, among other platinum metals, looks rather ordinary, then from the point of view of classical chemistry (we emphasize, classical inorganic chemistry, and not the chemistry of complex compounds), this element is very significant.

First of all, for him, unlike most elements of group VIII, valence 8+ is characteristic, and he forms stable tetroxide OsO 4 with oxygen. This is a kind of compound, and, apparently, it is not by chance that element No. 76 got its name, which is based on one of characteristic properties its tetroxides.

Osmium is detected by smell

Such a statement may seem paradoxical: after all, we are not talking about a halogen, but about a platinum metal ...

The history of the discovery of four of the five platinoids is associated with the names of two English scientists, two contemporaries. William Wollaston in 1803...1804 discovered palladium and rhodium, and another Englishman, Smithson Tennant (1761 ... 1815), in 1804 - iridium and osmium. But if Wollaston found both “his” elements in that part of raw platinum that was dissolved in aqua regia, then Tennant was lucky when working with the insoluble residue: as it turned out, it was a natural alloy of iridium and osmium.

The same residue was studied by three well-known French chemists - Collet-Descoti, Fourcroix and Vauquelin. They began their research even before Tennant. Like him, they observed the release of black smoke when raw platinum was dissolved. Like him, they, by fusing the insoluble residue with caustic potash, managed to obtain compounds that still managed to be dissolved. Fourcroix and Vauquelin were so convinced that there was a new element in the insoluble residue of crude platinum that they gave it a name in advance - pten - from the Greek πτηνος - winged. But only Tennant managed to separate this residue and prove the existence of two new elements - iridium and osmium.

The name of element #76 comes from Greek wordοσμη, meaning "smell". An unpleasant irritating smell, similar to the smells of chlorine and garlic at the same time, appeared when the product of fusion of osmiridium with alkali was dissolved. The carrier of this smell was osmium anhydride, or osmium tetroxide OsO 4 . Later it turned out that osmium itself can smell just as bad, although much weaker. Finely ground, it gradually oxidizes in air, turning into OsO 4 ...

Osmium metal

Osmium is a tin-white metal with a grayish-blue tint. It is the heaviest of all metals (its density is 22.6 g/cm3) and one of the hardest. However, the osmium sponge can be ground into a powder because it is fragile. Osmium melts at a temperature of about 3000 ° C, and its boiling point has not yet been precisely determined. It is believed to lie somewhere around 5500°C.

The great hardness of osmium (7.0 on the Mohs scale) is perhaps one of its physical properties that is most widely used. Osmium is introduced into the composition of hard alloys with the highest wear resistance. In expensive fountain pens, soldering on the tip of the pen is made from alloys of osmium with other platinum metals or with tungsten and cobalt. Similar alloys are used to make small parts of precision measuring instruments that are subject to wear. Small - because osmium is not widely distributed (5 10 -6% of the weight of the earth's crust), scattered and expensive. This also explains the limited use of osmium in industry. It goes only where, with a small amount of metal, you can get a big effect. For example, in chemical industry, which is trying to use osmium as a catalyst. In hydrogenation reactions organic matter osmium catalysts are even more efficient than platinum ones.

A few words about the position of osmium among other platinum metals. Outwardly, it differs little from them, but it is osmium that has the most high temperatures melting and boiling among all the metals of this group, it is he who is the heaviest. It can also be considered the least "noble" of the platinoids, since it is oxidized by atmospheric oxygen already at room temperature (in a finely divided state). And osmium is the most expensive of all platinum metals. If in 1966 platinum was valued on the world market 4.3 times more expensive than gold, and iridium - 5.3 times, then the similar coefficient for osmium was 7.5.

Like other platinum metals, osmium exhibits several valences: 0, 2+, 3+, 4+, 6+ and 8+. Most often you can find compounds of tetra- and hexavalent osmium. But when interacting with oxygen, it exhibits a valence of 8+.

Like other platinum metals, osmium is a good complexing agent, and the chemistry of osmium compounds is no less diverse than, say, that of palladium or ruthenium.

Anhydride and others

Undoubtedly, the most important compound of osmium remains its tetroxide OsO 4 , or osmium anhydride. Like elemental osmium, OsO 4 has catalytic properties; OsO 4 is used in the synthesis of the most important modern drug - cortisone. At microscopic studies animal and plant tissues, osmium tetroxide is used as a coloring agent. OsO 4 is very toxic, it strongly irritates the skin, mucous membranes and is especially harmful to the eyes. Any work with this useful substance requires extreme caution.

Outwardly, pure osmium tetroxide looks quite ordinary - pale yellow crystals, soluble in water and carbon tetrachloride. At a temperature of about 40°C (there are two modifications of OsO 4 with close melting points), they melt, and at 130°C, osmium tetroxide boils.

Another osmium oxide - OsO 2 - black powder insoluble in water - practical value does not have. Also not found yet practical application and other known compounds of element No. 76 - its chlorides and fluorides, iodides and oxychlorides, OsS 2 sulfide and OsTe 2 telluride - black substances with a pyrite structure, as well as numerous complexes and most osmium alloys. The only exceptions are some alloys of element No. 76 with other platinum metals, tungsten and cobalt. Their main consumer is instrumentation.

How is osmium obtained

Native osmium is not found in nature. It is always associated in minerals with another platinum group metal, iridium. There is a whole group of osmic iridium minerals. The most common of them is nevyanskite, a natural alloy of these two metals. It contains more iridium, which is why nevyanskite is often called simply osmium iridium. But another mineral - sysertskite - is called iridide osmium - it contains more osmium ... Both of these minerals are heavy, with a metallic sheen, and this is not surprising - such is their composition. And it goes without saying that all minerals of the osmic iridium group are very rare.

Sometimes these minerals are found independently, but more often osmium iridium is a part of native raw platinum. The main reserves of these minerals are concentrated in the USSR (Siberia, the Urals), the USA (Alaska, California), Colombia, Canada, and the countries of South Africa.

Naturally, osmium is mined together with platinum, but the refining of osmium differs significantly from the methods for isolating other platinum metals. All of them, except for ruthenium, are precipitated from solutions, while osmium is obtained by distillation of it with respect to the volatile tetroxide.

But before OsO 4 is distilled off, osmium iridium must be separated from platinum, and then iridium and osmium must be separated.

When platinum is dissolved in aqua regia, the minerals of the osmic iridium group remain in the sediment: even this solvent of all solvents cannot overcome these most stable natural alloys. To bring them into solution, the precipitate is alloyed with eight times the amount of zinc - this alloy is relatively easy to turn into powder. The powder is sintered with barium peroxide BaO 3 , and then the resulting mass is treated with a mixture of nitric and hydrochloric acids directly in the distillation apparatus to distill OsO 4 .

It is captured with an alkaline solution and a salt of the composition Na 2 OsO 4 is obtained. A solution of this salt is treated with hyposulfite, after which osmium is precipitated with ammonium chloride in the form of the Fremy salt Cl 2 . The precipitate is washed, filtered and then ignited in a reducing flame. In this way, as yet insufficiently pure spongy osmium is obtained.

Then it is purified by treatment with acids (HF and HCl) and is further reduced in an electric furnace in a hydrogen jet. After cooling, the metal is obtained with a purity of up to 99.9% O 3 .

This is the classical scheme for obtaining osmium - a metal that is still used very limitedly, a very expensive metal, but quite useful.

The more, the... more

Natural osmium consists of seven stable isotopes with mass numbers 184, 186 ... 190 and 192. An interesting pattern: the larger the mass number of an osmium isotope, the more common it is. The share of the lightest isotope, osmium-184, is 0.018%, and the heaviest, osmium-192, is 41%. Of the man-made radioactive isotopes of element 76, the longest-lived is osmium-194, with a half-life of about 700 days.

Osmium carbonyls

In recent years, chemists and metallurgists are increasingly interested in carbonyls - compounds of metals with CO, in which the metals are formally zerovalent. Nickel carbonyl is already quite widely used in metallurgy, and this allows us to hope that other similar compounds will eventually be able to facilitate the production of certain valuable materials. Two carbonyls are now known for osmium. Pentacarbonyl Os(CO) 5 - in normal conditions colorless liquid (melting point - 15°C). Get it at 300°C and 300 atm. from osmium tetroxide and carbon monoxide. At normal temperature and pressure, Os(CO) 5 gradually transforms into another carbonyl composition Os 3 (CO) 12 - yellow crystalline substance melting at 224°C. The structure of this substance is interesting: three osmium atoms form an equilateral triangle with faces 2.88 Å long, and four CO molecules are attached to each vertex of this triangle.

Fluorides controversial and undisputed

“Fluorides OsF 4 , OsF 6 , OsF 8 are formed from elements at 250...300°C... OsF 8 is the most volatile of all osmium fluorides, bp. 47.5 ° "... This quote is taken from the III volume of the Brief Chemical Encyclopedia, published in 1964. But in the III volume of the Fundamentals of General Chemistry, B.V. Nekrasov, published in 1970, the existence of osmium octafluoride OsF 8 is rejected. We quote: “In 1913, two volatile osmium fluorides were first obtained, described as OsF 6 and OsF 8 . So it was believed until 1958, when it turned out that in reality they correspond to the formulas OsF 5 and OsF 6 . Thus, for 45 years featured in scientific literature OsF 8 never actually existed. Similar cases of "closing" of the previously described connections are not so rare.

Note that the elements also sometimes have to be “closed” ... It remains to be added that, in addition to those mentioned in the Brief Chemical Encyclopedia, another osmium fluoride was obtained - unstable OsF 7 . This pale yellow substance at temperatures above –100°C decomposes into OsF 6 and elemental fluorine.

The dumbbells and barbells used by bodybuilders to pump up their muscles are made of steel. Made from lead - or better from - shells would lose significantly in volume. But it is even more accurate to use osmium for the production of weights: a kilogram of osmium is a small ball that fits easily in a clenched fist. A half-liter bottle with powdered osmium (it is in this form that the noble metal leaves the walls enrichment enterprise) weighs noticeably more than a bucket of water.

That's just pouring from osmium weights the brave cannot be found: it is painfully refractory. And the cost of the metal is such that an athletic club would have to work for three hundred years to buy one osmium dumbbell ...

Osmium is not enough!

In nature, osmium occurs mainly in the form of a combination with iridium, which is part of either native platinum or platinum-palladium ore. Minerals considered raw materials for the extraction of osmium contain, on average, one thousandth of a percent of the heavy "relative" of platinum. For all the time of exploration, not a single osmium nugget was mined - even the smallest size.

The small amount and difficulty of obtaining osmium determines the height of its price. Half a century ago, osmium was valued at seven to eight times the price of gold. Speculation recent years led to absolutely insane offers: a gram of osmium was sold for both 10 thousand and 200 thousand dollars. Sold - but not sold: osmium does not find active use, although it is used in some places.

The discovery of osmium

W. Wollaston was close to the discovery of osmium, experimenting with platinum ores. The Frenchmen Antoine de Fourcroix and Louis-Nicolas Vauquelin, inspired by his successes, took up their own research and correctly assumed the existence of a new element, which evaporated in the form of black smoke during experiments.

Fourcroix and Vauquelin gave the substance the name "pten" - which means "volatile", and calmed down in anticipation of recognition. However, the English chemist Smithson Tennant divided "ptene" into two related metals, one of which, for the variety of colors of its compounds, called iridium, and the second - because of the annoying stink - osmium.

These important events in the year 1803, generous with discoveries.

Osmium properties

The melting and boiling points until recently were considered conditionally equal to 3000° and 5000°C: there were no means for full-scale verification of calculations. Only a few years ago it was possible to clarify the physical parameters of the metal. It turned out that it is better to cook osmium alloys on the surface of the Sun ...

interesting appearance osmium. Solidifying from the melt, osmium forms hard and brittle crystals, the silvery sheen of which is shaded by a grayish-blue (and even blue) tint. The external advantages of osmium could attract jewelers, however, the high chemical activity of the metal and the toxicity of its compounds exclude the possibility of using this platinoid in jewelry.

Application of osmium

Osmium catalysts are used in hydrogenation organic compounds, in the production of drugs, in the synthesis of ammonia. True, the high cost of the metal makes industrialists look for affordable substitutes, and today osmium is less and less common in the chemical industry.

From solid and non-magnetic osmium, axles, supports and support sockets for high-precision measuring instruments are made. And although ruby ​​supports are harder and cheaper than osmium ones, the resistance of the metal is sometimes preferred for instrumentation.

Osmium is dangerous and requires caution

It is almost impossible to avoid osmium oxidation if the metal comes into contact with atmospheric oxygen. Therefore, about any use of osmium in

Ordinal element with atom number 76 in chemical system DI. Mendeleev called osmium. In solid form, the metal is a brilliant silver-white color with bluish tints. Considered a heavy metal, the density of osmium is 22.6 g/cm3. But at the same time, it is fragile and can be made into a powder. It was in this state that the metal was discovered by the English chemist S. Tennant. Transition metal, part of the platinum group. In a fine state, it can be oxidized at room temperature.

Osmium properties

The precious metal is the most dense (22.61 g/cm3) and refractory. The physical properties of osmium are as follows:

1. Melts at 3047°C, boils at 5025°C, not recyclable mechanically, cannot be dissolved in acid and "royal vodka".

2. It has an unpleasant smell, reminiscent of a mixture of garlic and bleach, added to give the platinum alloy hardness and elasticity.

3. Atomic mass osmium is 190.23 g/mol.

4. The 187 isotope is the result of the decay of the isotope of rhenium. Due to its chemical inertness, osmium alloy is used in an aggressive acidic environment.

5. The metal is well ground, in the form of a powder purple dissolves slowly in acids, reacts with compounds such as sulfur, selenium, tellurium and phosphorus.

6. In a friable state, it reacts with mercury, resulting in osmium amalgam.

7. When interacting with other substances, it emits a bad smell.

8. Externally, the crystals look beautiful. After influencing him high temperature it melts, forming hard and brittle crystals. The color of the metal is gray-blue with a silvery sheen.

Jewelers could appreciate its external data, but due to its toxicity and chemical interaction with other elements, it is not used for jewelry production.

The earth's crust is 0.5% of this metal, mainly in the center of the earth - the core. A piece of metal, like an egg, weighs one kilogram. If a powder of this substance is poured into a container of 0.5 liters, its weight will be 16 kg.

The chemical properties of the noble metal are as follows:

• in the solid state, it oxidizes at a temperature of more than 400 C, in the powder it already reacts at room temperature (OsO4);
• when heated, interacts with sulfur, chlorine, fluorine, sulfur and other chemical elements;
• it does not dissolve in boiling hydrochloric acid, but in a finely divided form it combines with nitric acid molecules and oxidizes: Os + 8HNO3 = OsO4 + 4H2O + 8NO2;
• black osmium dioxide OsO2 is isolated by dehydration in a nitrogen atmosphere;
• Osmium (IV) hydroxylOs(OH)4 (OsO2 2H2O) is obtained by reduction of metal(VI) salts.

There are six isotopes in nature, one of the 186 isotopes decays into compounds of the alpha group. Osmium has the longest existence - 194 with a half-life of two years. Osmium differs little from its counterparts in the platinoids group (ruthenium, palladium, osmium, iridium, platinum), but surpasses other metals because of its density and ability to boil at a very high temperature.

It occurs in nature in native form as a solid solution with iridium (minerals nevyanskite and sysertskite).

Application

The addition of osmium to various alloys makes them more stable, durable, not subject to mechanization and corrosion.

1. Electrochemical industry: used in tungsten, nickel and cobalt compounds. All products are durable.
2. The introduction of a platinum group metal into metal products increases their strength. Very little substance is needed to create sharp blades, medical products and technical products.
3. Fountain pens with tips do not wear out for a long time.
4. In cardiology: the metal found its purpose in implants (pacemaker) and in the replacement of valves in the pulmonary trunk.
5. In combination with tungsten, it is used to produce filaments for electric lamps.
6. It does not have a magnetic attraction, due to which it has found its application in the manufacture of watch parts.
7. Catalysts from it are used in the manufacture of medicines, ammonia is synthesized. The highest oxide of this metal is used in the production of artificial drugs and in the laboratory - they stain tissues under a microscope.
8. Solid metal is used in the manufacture of supports and axles for high-precision measuring instruments. Due to its hardness, metal is used in instrument making.
9. Osmium 187 and other isotopes are used in heavy industry: rocketry, airliners, military equipment. Thanks to its wear resistance, it helps to withstand extreme conditions.

Discovery history

Osmium is a noble metal. But this contradicts its status: in Greek, “osme” means smell, that is, chemically active. And nobility implies the inertness of this substance.

Osmium was discovered in 1803. The English chemist S. Tennant, in collaboration with William H. Wollaston, experimented with dissolving osmium in aqua regia, but nothing came of it. Similar tests were carried out by French chemists Collet-Descoti, Antoine de Fourcroix and Vauquelin. They found in this element an insoluble precipitate of platinum ore. chemical element given the name Pten, from the Greek word means flying. By this experience they proved the presence of two chemical substances- osmium and iridium.

Where is it in nature and how is it obtained

In nature, the noble metal does not exist in nuggets. It is mined from the following rocks - sysertskite, nevyanskite, osmiiride and sarsite. It is a part of copper, molybdenum and nickel ores. According to some reports, it is found in arsenic and sulfur compounds.

The share of matter on the planet is 0.000005% of the total mass of all rocks. In nature, osmium combines with iridium, the percentage of which ranges from 10 to 50. There are reserves of this metal in Africa, Tasmania, Australia, the United States, Canada, Colombia, and Russia. The most rich country in terms of osmium content - South Africa (deposit of the Bushveld complex). The noble metal can be found in alloys of native platinum, but more often in alloys of osmium and iridium.

The crumbly state is the most acceptable form of existence. In this form, he better enters into chemical reactions and is subjected heat treatment. Platinum group metal can be obtained in the following ways:

• use of an electron beam;
• arc heating;
• application of crucibleless zone melting.

Crystals received the last way very expensive. Someone has managed to grow crystals from powder, but the method is difficult and time consuming.

Price

In nature, there is quite a bit of metal, and extracting osmium is a costly project, so its price in the market is due to this. In the 60-70s of the XX century, the precious metal was several times more expensive than gold. They sold it cheaply, but it was valued dearly, because of this, the offers on the market were stunning: a gram of metal was estimated at 10 thousand, and for 200 thousand dollars. Gold is not valued as much as its fellow platinum group.

Why is osmium dangerous?

The chemical compound with osmium damages human organs. Inhalation of vapors leads to lethal outcome. In animals with intoxication, anemia was observed, and lung function was impaired.

Do you know that osmium tetra oxide OsO4 is a rather aggressive compound, and if it is poisoned, green or black bubbles appear on the skin. It is not easy for a person, because it will take a long time to be treated.

Those who work in hazardous industries should be careful about themselves. To do this, the enterprises issue protective suits and respirators.