Which precious metal do you think is considered the heaviest? Yes, this is an element of the periodic table designated Os. The density of osmium is the highest among all metals. In the article we will analyze all the characteristic properties of this element, talk about its prevalence, production and practical application.
What is it?
The word "osmium" comes from lat. Osmium This is one of the chemical elements in the periodic table, concluded at number 76. The density of osmium affects both scientists and just curious. It is the largest among all the simple substances that are found in nature. Only iridium can "compete" with him here. However, theoretical studies have shown that the density of osmium is higher than the density of this element.
Os is a standard white, silver, shiny metal with a characteristic blue tint. It is classified as platinum, transitional.
origin of name
Before proceeding to the properties of osmium, let us consider a rather interesting history of the origin of the name of this metal. It comes from other Greek. ὀσμή, which means "smell." Why?
The fact is that the chemical reactions of the dissolution of the alkaline compounds of osmiridium (the so-called insoluble residue of platinum in "aqua regia") in acid or water are always accompanied by the release of an unpleasant persistent odor that irritates the human throat. In some ways, it is comparable to the “aromas” of rotten radish or chlorine.
Discovery story
Osmium (metal photos are presented in the article) was discovered in 1803 by Smithson Tennant and William H. Wollaston, English chemical scientists. They found an element in the sediment formed after the dissolution of platinum in "aqua regia".
It should be noted that similar studies were conducted by French scientists: Colle Descoti, Vauclin, Antoine de Fourcroix. They also concluded that an unknown substance was contained in the insoluble platinum precipitate.
French researchers proposed the name pten to this hypothetical element (from the Greek. Πτηνος - "winged"). But Tennant was the first to demonstrate with his experiments that this residue is a mixture of osmium and iridium.
The discovery of these two elements at once was documented by the Englishman in his letter to the Royal Society of London, sent July 22, 1804.
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Osmium is a silver-bluish, dense, but at the same time rather fragile metal. It has a high specific gravity, it is able to maintain gloss even at high temperatures.
Due to its brittleness, hardness, and low vapor pressure (it is the lowest in osmium in platinum metals), as well as due to the high melting point, this element is difficult to machine.
What does osmium density mean?
We now turn to the most remarkable characteristic of this metal. Osmium is the densest of all the simple substances that are currently discovered by scientists. But in this indicator, it only slightly exceeds iridium.
The most reliable indicators for this characteristic for both metals were calculated by the parameters of their crystal lattice. The density of the rare metal osmium is 22.587 ± 0.009 g / cm³. For iridium, the value is only slightly less - 22.562 ± 0.009 g / cm³.
If we turn to the most modern studies, we can see that the density of osmium (kg / m3) is 22600. Scientists have compared various isotopes of the element. The densest among them was recognized as 192 Os.
What does osmium density 22600 kg / m3 mean? This is a consequence of lanthanoid compression and close-packed hexagonal crystal lattice.
Physical properties of an element
We are now aware that the density of the rare metal osmium is 22,600 kg / m 3 . Consider his other physical characteristics:
- The melting point of the metal is 3033 ° Celsius.
- Boiling point - 5012 ° .
- The transition temperature of a substance into a superconducting state is 0.66 K.
- Mohs hardness is 7.
- The hardness of the element according to Vickers is 3-4 GPa.
- The modulus of normal elasticity of the metal is 56.7 GPa.
- Its shear modulus is 22 GPa.
- Osmium is a paramagnet (its magnetic susceptibility is estimated at 9.9 · 10 −6 ).
Chemical properties of metal
Once again, the density of the rare metal osmium is 22600 kg / m 3 . Now we denote the chemical properties of this element:
- When heated, the metal powder will react with oxygen, sulfur fumes, halogens, tellurium, selenium, phosphorus, sulfuric and nitric acids.
- Compact osmium will not interact with alkalis and acids. But at the same time it will form water-soluble osmata with alkali melts.
- Osmium slowly reacts with “aqua regia” and nitric acid.
- The metal will react in the presence of oxidizing agents (potassium chlorate or nitrate) with molten sodium peroxide.
- In compounds, it exhibits oxidation states from −2 to +8. Of these, the most common for osmium are +2, +3, +4 and +8.
- This is one of the few metals that can form cluster (polynuclear) compounds. For example, the polynuclear carbonyl of the Os 3 (CO) 12 element is used to study and simulate hydrocarbon reactions at metal centers.
Finding metal in nature
This element is distinguished not only by the fact that the density of the rare metal osmium is 22600 kg / m 3 . It is one of the most common in nature. Its content in the earth's crust is about 5 · 10 −6 % by mass.
In the native form, osmium can be found in the form of solid solutions with iridium (they can contain from 10 to 50% osmium). The element is also found in polymetallic ores containing both palladium and platinum. These are copper-molybdenum and copper-nickel sulfide ores. Osmium is also found in platinum minerals, as well as waste obtained after processing gold-bearing ore.
The main minerals of osmium belong to the class of solid solutions. These are alloys of iridium and osmium - syrsertskite and nevyanskite. As for the latter, it forms dense (compare: ρ = 17,000–22,000 kg / m 3 ) light gray or whitish lamellar crystals of hexagonal syngony, whose Mohs hardness is estimated at 6 points. The percentage of osmium in nevyanskite is from 21 to 43% of the total mass.
Sysertskit can often be found close to Nevyanskite. Outwardly, it will be grayish crystals of a hexagonal structure. On the Mohs scale, their hardness is estimated at 6 points. The density is 17 800-22 500 kg / m 3 . The peculiarity of this mineral is that it can contain not only iridium and osmium, but also ruthenium.
In some examples, these minerals are found independently. But in most cases, osmotic iridium is still part of the platinum nuggets.
You can also find osmium in the form of compounds with arsenic and sulfur. This arsarsite, erlichmanite, osmium lapis lazuli. However, the osmium content in ores will not exceed 1 · 10 −5 .
Environmental prevalence
Studies by scientists show that osmium is one of the rarest elements found in nature. This statement is confirmed by specific figures:
- The prevalence in the earth's crust is about 0.007 g / t.
- The content in eclogites is 0.16 g / t.
- The presence of pyroxenites in the formations is about 0.007 g / t.
- The content in peridotites is about 0.15 g / t.
- The presence of peridotite dunites in the formations is 0.0013 g / t.
Osmium deposits
The largest deposits of osmist iridium in the world are recorded in these zones:
- Ural and Siberia of the Russian Federation.
- Alaska and California (USA).
- Canada.
- Colombia.
- A number of countries in South Africa.
- Australia.
- Tasmania.
The largest field today is the Bushveld complex, located in the Republic of South Africa.
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In the industry, osmium is released from the enriched raw materials of platinum metal. This happens by calcining this concentrate in air at sufficiently high temperatures, reaching 800-900 ° C. Quantitative sublimation of osmium tetraoxide OsO 4, characterized by increased volatility, occurs. Then they are absorbed with a NaOH solution.
With further evaporation of the solution, salt - sodium perosmate is isolated. Then it is reduced with hydrogen when heated to +120 degrees Celsius to osmium. It turns out in the form of a sponge.
Application
Now let's see how applicable the most dense of the open metals in human practice:
- Exceptional refractoriness as well as high hardness make it possible to use osmium as a coating on various friction units.
- It can be used as a catalyst in the synthesis of ammonia, for the hydrogenation of organic compounds. Also used in methanol fuel catalysts.
- The alloy of tungsten and osmium osram was used for some time to make filaments for incandescent lamps.
- There is information about the use of osmium for military purposes - as part of missile warheads and artillery shells.
- It is used in electronic equipment installed in aircraft and rocket technology.
- In conjunction with ruthenium and iridium, it is a component of wear-resistant and heavy-duty alloys.
- Osmium tetraoxide is used in electron microscopy to firmly fix biological research objects.
- The alloy of osmium (10%) and platinum (90%) is used in surgery for the manufacture of implants - pacemakers, when replacing the valves of the pulmonary trunk.
- Alloys of aluminum with osmium are also known. Their practical applicability is based on unusually high ductility. So, an element of this alloy can be extended 2 times without breaking.
Physiological effect, biological role
Scientists are sure today that osmium does not play any biological role. But at the same time he is classified as extremely aggressive. Along with mercury, bismuth and beryllium.
Even a small amount of osmium vapor in the air causes eye damage in people - conjunctivitis, lacrimation, pain. In this case, an unpleasant metallic taste appears in the mouth, bronchial spasms begin. It becomes difficult for a person to breathe. Even a few hours after the source of the vapor release is eliminated.
With prolonged exposure to element vapors on the human body, blindness, diseases of the respiratory and nervous systems, impaired renal and gastrointestinal tract can occur. Not even a fatal outcome is possible.
The effects of osmium also affect the skin. They acquire a greenish, or even a blackish tint, wounds, blisters and other inflammations appear. The skin loses its sensitivity, can die. In this case, the ulcers remaining from the effects of osmium on the human body heal for a very long time.
Osmium is the densest metal in the world. This quality makes it possible to use the element in industry in a wide variety of fields. But osmium is also a rather rare precious metal.