Helium is a truly noble gas. It has not yet been possible to force him into any reaction. The helium molecule is monatomic. In terms of lightness, this gas is second only to hydrogen; air is 7.25 times heavier than helium. Helium is almost insoluble in water and other liquids. And in the same way, not a single substance dissolves noticeably in liquid helium.
Solid helium cannot be obtained at any temperature unless the pressure is increased.
In the history of the discovery, research and application of this element, the names of many prominent physicists and chemists from different countries can be found. The following people were interested in helium and worked with helium: Jansen (France), Lockyer, Ramsay, Crookes, Rutherford (England), Palmieri (Italy), Keesom, Kamerlingh-Onnes (Holland), Feynman, Onsager (USA), Kapitza, Kikoin, Landau ( Soviet Union) and many other prominent scientists.
The unique appearance of the helium atom is determined by the combination of two amazing natural structures - absolute champions in compactness and strength. In the core of helium, helium-4, both intranuclear shells are saturated - both proton and neutron. The electronic doublet framing this core is also saturated. These designs hold the key to understanding the properties of helium. This is the source of its phenomenal chemical inertness and the record small size of its atom.
The role of the nucleus of the helium atom - the alpha particle - is enormous in the history of the formation and development of nuclear physics. If you remember, it was the study of the scattering of alpha particles that led Rutherford to the discovery of the atomic nucleus. By bombarding nitrogen with alpha particles, the interconversion of elements was accomplished for the first time - something that many generations of alchemists had dreamed about for centuries. True, in this reaction it was not mercury that turned into gold, but nitrogen into oxygen, but this is almost as difficult to do. The same alpha particles were involved in the discovery of the neutron and the production of the first artificial isotope. Later, curium, berkelium, californium, and mendelevium were synthesized using alpha particles.
We have listed these facts for only one purpose - to show that element No. 2 is a very unusual element.
Earth's helium
Helium is an unusual element, and its history is unusual. It was discovered in the solar atmosphere 13 years earlier than on Earth. More precisely, a bright yellow D line was discovered in the spectrum of the solar corona, and what was hidden behind it became reliably known only after helium was extracted from earthly minerals containing radioactive elements.
There are 29 isotopes in the earth's crust, the radioactive decay of which produces alpha particles - highly active, high-energy nuclei of helium atoms.
Basically, terrestrial helium is formed during the radioactive decay of uranium-238, uranium-235, thorium and unstable products of their decay. Incomparably smaller amounts of helium are produced by the slow decay of samarium-147 and bismuth. All these elements produce only the heavy isotope of helium - 4 He, whose atoms can be considered as the remains of alpha particles, buried in a shell of two paired electrons - in an electron doublet. In early geological periods, there were probably other naturally radioactive series of elements that had already disappeared from the face of the Earth, saturating the planet with helium. One of them was the now artificially recreated neptunium series.
By the amount of helium locked in a rock or mineral, one can judge their absolute age. These measurements are based on the laws of radioactive decay: for example, half of uranium-238 turns into helium and lead.
Helium accumulates slowly in the earth's crust. One ton of granite containing 2 g of uranium and 10 g of thorium produces only 0.09 mg of helium - half a cubic centimeter - over a million years. The very few uranium- and thorium-rich minerals have quite high helium contents—several cubic centimeters of helium per gram. However, the share of these minerals in natural helium production is close to zero, since they are very rare.
Helium pi The Sun was discovered by the Frenchman J. Jansen, who carried out his observations in India on August 10, 1868, and the Englishman J. Lockyer on October 20 of the same year. Letters from both scientists arrived in Paris on the same day and were read at a meeting of the Paris Academy of Sciences on October 26, with an interval of several minutes. Academicians, amazed by such a strange coincidence, decided to knock out a gold medal in honor of this event.
Natural compounds that contain alpha-active isotopes are only a primary source, but not a raw material for the industrial production of helium. True, some minerals with a dense structure - native metals, magnetite, garnet, apatite, zircon and others - firmly retain the helium contained in them. However, over time, most minerals undergo processes of weathering, recrystallization, etc., and helium leaves them.
Helium bubbles released from crystalline structures set off on a journey across the earth's crust. A very small part of them dissolves in groundwater. To form more or less concentrated helium solutions, special conditions are needed, primarily high pressures. Another part of the wandering helium escapes into the atmosphere through the pores and cracks of minerals. The remaining gas molecules fall into underground traps, where they accumulate for tens or hundreds of millions of years. The traps are layers of loose rocks, the voids of which are filled with gas. The bed for such gas reservoirs is usually water and oil, and on top they are covered by gas-impermeable strata of dense rocks.
Since other gases (mainly methane, nitrogen, carbon dioxide) also travel in the earth’s crust, and in much larger quantities, pure helium accumulations do not exist. Helium is present in natural gases as a minor impurity. Its content does not exceed thousandths, hundredths, and rarely tenths of a percent. Large (1.5-10%) helium content of methane-nitrogen deposits is an extremely rare phenomenon.
Natural gases turned out to be practically the only source of raw materials for the industrial production of helium. To separate it from other gases, the exceptional volatility of helium, associated with its low liquefaction temperature, is used. After all other components of the natural gas have condensed during deep cooling, the helium gas is pumped out. It is then cleaned of impurities. The purity of factory helium reaches 99.995%.
Helium reserves on Earth are estimated at 54,014 m3; judging by calculations, tens of times more of it was formed in the earth’s crust over 2 billion years. This discrepancy between theory and practice is quite understandable. Helium is a light gas and, like hydrogen (although more slowly), it evaporates from the atmosphere into outer space. Probably, during the existence of the Earth, the helium of our planet was repeatedly renewed - the old one evaporated into space, and instead of it, fresh helium entered the atmosphere - “exhaled” by the Earth.
There is at least 200 thousand times more helium in the lithosphere than in the atmosphere; Even more potential helium is stored in the “womb” of the Earth - in alpha-active elements. But the total content of this element in the Earth and atmosphere is small. Helium is a rare and diffuse gas. There is only 0.003 mg of helium per 1 kg of earthly material, and its content in the air is 0.00052 percent by volume. Such a low concentration does not yet allow for economical extraction of helium from the air.
Inert but much needed helium
At the end of the last century, the English magazine Punch published a cartoon in which helium was depicted as a slyly winking little man - an inhabitant of the Sun. The text under the picture read: “Finally, I was caught on Earth! This went on long enough! I wonder how long it will take until they figure out what to do with me?”
Indeed, 34 years passed from the discovery of terrestrial helium (the first report of this was published in 1881) before it found practical use. A certain role here was played by the original physical, technical, electrical and, to a lesser extent, chemical properties of helium, which required a long study. The main obstacles were the dissipation and high cost of element No. 2. That is why helium was not available in practice.
The Germans were the first to use helium. In 1915, they began filling their airships that bombed London with it. Soon, lightweight but non-flammable helium became an indispensable filler for aeronautical vehicles. The decline in airship construction that began in the mid-30s led to some decline in helium production, but only for a short time. This gas increasingly attracted the attention of chemists, metallurgists and mechanical engineers.
Many technological processes and operations cannot be carried out in air. To avoid interaction of the resulting substance (or feedstock) with air gases, special protective environments are created; and there is no more suitable gas for these purposes than helium.
Inert, lightweight, mobile, and a good conductor of heat, helium is an ideal means for pressing flammable liquids and powders from one container to another; It is these functions that it performs in missiles and guided missiles. Individual stages of producing nuclear fuel take place in a helium protective environment. Fuel elements of nuclear reactors are stored and transported in containers filled with helium. With the help of special leak detectors, the action of which is based on the exceptional diffusion ability of helium, they identify the slightest possibility of leakage in nuclear reactors or other systems under pressure or vacuum.
Recent years have been marked by a renewed rise in airship construction, now on a higher scientific and technical basis. In a number of countries, airships with helium filling with a carrying capacity of 100 to 3000 tons have been built and are being built. They are economical, reliable and convenient for transporting large-sized cargo, such as strings of gas pipelines, oil refineries, power line supports, etc. Filling with 85% helium and 15% hydrogen is fireproof and only reduces lift by 7% compared to hydrogen filling.
High-temperature nuclear reactors of a new type, in which helium serves as the coolant, have begun to operate.
Liquid helium is widely used in scientific research and technology. Ultra-low temperatures favor in-depth knowledge of matter and its structure - at higher temperatures, subtle details of energy spectra are masked by the thermal movement of atoms.
There already exist superconducting solenoids made from special alloys that create strong magnetic fields at liquid helium temperatures (up to 300 thousand oersteds) with negligible energy consumption.
At the temperature of liquid helium, many metals and alloys become superconductors. Superconducting relays - cryotrons - are increasingly used in the designs of electronic computers. They are simple, reliable, and very compact. Superconductors, and with them liquid helium, are becoming necessary for electronics. They are included in the designs of infrared radiation detectors, molecular amplifiers (masers), optical quantum generators (lasers), and instruments for measuring ultrahigh frequencies.
Of course, these examples do not exhaust the role of helium in modern technology. But if it were not for the limited nature of natural resources and the extreme dissipation of helium, it would have found many more applications. It is known, for example, that when canned in helium, food products retain their original taste and aroma. But “helium” canned food still remains a “thing in itself”, because there is not enough helium and it is used only in the most important industries and where it cannot be done without it. Therefore, it is especially offensive to realize that with flammable natural gas, much larger quantities of helium pass through chemical synthesis apparatuses, furnaces and furnaces and escape into the atmosphere than those extracted from helium-bearing sources.
Now it is considered profitable to release helium only in cases where its content in natural gas is not less than 0.05%. The reserves of such gas are constantly decreasing, and it is possible that they will be exhausted before the end of this century. However, the problem of “helium deficiency” will probably be solved by this time - partly through the creation of new, more advanced methods for separating gases, extracting from them the most valuable, although insignificant in volume, fractions, and partly thanks to controlled thermonuclear fusion. Helium will become an important, albeit by-product, of the activity of “artificial suns”.
ISOTOPES OF HELIUM. There are two stable isotopes of helium in nature: helium-3 and helium-4. The light isotope is distributed on Earth a million times less than the heavy one. This is the rarest stable isotope existing on our planet. Three more isotopes of helium have been obtained artificially. They are all radioactive. The half-life of helium-5 is 2.440-21 seconds, helium-6 is 0.83 seconds, helium-8 is 0.18 seconds. The heaviest isotope, interesting because in its nuclei there are three neutrons per proton, was first obtained in Dubna in the 60s. Attempts to obtain helium-10 have so far been unsuccessful.
THE LAST SOLID GAS. Helium was the last of all gases to be converted into liquid and solid states. The particular difficulties of liquefying and solidifying helium are explained by the structure of its atom and some features of its physical properties. In particular, helium, like hydrogen, at temperatures above - 250°C, when expanding, does not cool, but heats up. On the other hand, the critical temperature of helium is extremely low. That is why liquid helium was first obtained only in 1908, and solid helium in 1926.
HELIUM AIR. Air in which all or most of the nitrogen is replaced by helium is no longer news today. It is widely used on land, underground and under water.
Helium air is three times lighter and much more mobile than ordinary air. It behaves more actively in the lungs - it quickly supplies oxygen and quickly evacuates carbon dioxide. That is why helium air is given to patients with breathing disorders and some operations. It relieves suffocation, treats bronchial asthma and diseases of the larynx.
Breathing helium air practically eliminates nitrogen embolism (caisson disease), to which divers and specialists of other professions who work under conditions of high pressure are susceptible during the transition from high pressure to normal. The cause of this disease is quite significant, especially with high blood pressure, the solubility of nitrogen in the blood. As the pressure decreases, it is released in the form of gas bubbles, which can clog blood vessels, damage nerve nodes... Unlike nitrogen, helium is practically insoluble in body fluids, so it cannot cause decompression sickness. In addition, helium air eliminates the occurrence of “nitrogen narcosis,” which is externally similar to alcohol intoxication.
Sooner or later, humanity will have to learn to live and work on the seabed for a long time in order to seriously take advantage of the mineral and food resources of the shelf. And at great depths, as the experiments of Soviet, French and American researchers have shown, helium air is still indispensable. Biologists have proven that prolonged breathing of helium air does not cause negative changes in the human body and does not threaten changes in the genetic apparatus: the helium atmosphere does not affect the development of cells and the frequency of mutations. There are works whose authors consider helium air to be the optimal air medium for spacecraft making long flights into the Universe.
OUR HELIUM. In 1980, a group of scientists and specialists led by I. L. Andreev was awarded the State Prize for the creation and implementation of technology for producing helium concentrates from relatively poor helium-bearing gases. A helium plant was built at the Orenburg gas field, which became our main supplier of “solar gas” for the needs of various industries.
HELIUM COMPLEX. In 1978, Academician V. A. Legasov and his colleagues, during the decay of tritium nuclei included in the glycine amino acid molecule, managed to register a paramagnetic helium-containing complex in which a hyperfine interaction of a helium-3 nucleus with an unpaired electron was observed. This is the greatest achievement in helium chemistry so far.
Helium(lat. helium), symbol He, chemical element of group VIII of the periodic system, refers to inert gases; serial number 2, atomic mass 4.0026; colorless and odorless gas. Natural gas consists of two stable isotopes: 3he and 4he (the content of 4he sharply predominates).
For the first time, gas was discovered not on Earth, where it is scarce, but in the atmosphere of the Sun. In 1868, the Frenchman J. Jansen and the Englishman J. N. Lockyer studied the spectroscopic composition of solar prominences. The images they obtained contained a bright yellow line (the so-called d3 line), which could not be attributed to any of the elements known at that time. In 1871, Lockyer explained its origin by the presence of a new element in the Sun, which was called helium (from the Greek helios - Sun). On Earth, hydrogen was first isolated in 1895 by the Englishman W. Ramsay from the radioactive mineral kleveite. The spectrum of the gas released when heating kleveite showed the same line.
Helium in nature. There is little hydrogen on Earth: 1 m3 of air contains only 5.24 cm3 of hydrogen, and each kilogram of earthly material contains 0.003 mg of hydrogen. In terms of prevalence in the Universe, hydrogen ranks second after hydrogen: hydrogen accounts for about 23 % cosmic mass.
On Earth, hydrogen (more precisely, the isotope 4he) is constantly formed during the decay of uranium, thorium, and other radioactive elements (in total, the earth's crust contains about 29 radioactive isotopes that produce 4he).
Approximately half of all gas is concentrated in the earth’s crust, mainly in its granite shell, which accumulates the main reserves of radioactive elements. The content of hydrogen in the earth's crust is low - 3 × 10-7% by weight. Gas accumulates in free gas accumulations in the subsoil and in oils; Such deposits reach industrial scales. The maximum concentrations of gas (10-13%) were found in free gas accumulations and gases of uranium mines and (20-25%) in gases spontaneously released from groundwater. The older the age of gas-bearing sedimentary rocks and the higher the content of radioactive elements in them, the more gas there is in the composition of natural gases. Volcanic gases usually have a low G content.
Hydrocarbons are produced on an industrial scale from natural and petroleum gases of both hydrocarbon and nitrogen composition. Based on the quality of raw materials, helium deposits are divided into: rich (He content > 0.5% by volume); ordinary (0.10-0.50) and poor< 0,10). В СССР природный Г. содержится во многих нефтегазовых месторождениях. Значительные его концентрации известны в некоторых месторождениях природного газа Канады, США (шт. Канзас, Техас, Нью-Мексико, Юта).
In natural gas of any origin (atmospheric, from natural gases, from radioactive minerals, meteorites, etc.), the 4he isotope predominates. The content of 3he is usually low (depending on the source of the gas, it ranges from 1.3 × 10-4 to 2 × 10-8%) and only in gas isolated from meteorites does it reach 17-31.5%. The rate of formation of 4he during radioactive decay is low: in 1 ton of granite containing, for example, 3 g of uranium and 15 g of thorium, 1 mg of gas is formed in 7.9 million years; however, since this process occurs constantly, during the existence of the Earth it should have ensured that the content of hydrogen in the atmosphere, lithosphere, and hydrosphere significantly exceeds the existing one (it is about 5 × 1014 m3). This deficiency of G. is explained by its constant evaporation from the atmosphere. Light atoms of gas, entering the upper layers of the atmosphere, gradually acquire a speed there above the 2nd cosmic speed and thereby gain the opportunity to overcome the forces of gravity. The simultaneous formation and volatilization of gas leads to the fact that its concentration in the atmosphere is almost constant.
The 3he isotope, in particular, is formed in the atmosphere during the beta decay of the heavy isotope of hydrogen - tritium (T), which, in turn, arises from the interaction of neutrons from cosmic radiation with nitrogen in the air:
The nuclei of the 4he atom (consisting of 2 protons and 2 neutrons), called alpha particles or helions, are the most stable among compound nuclei. The binding energy of nucleons (protons and neutrons) in 4he has a maximum value compared to the nuclei of other elements (28.2937 MeV); therefore, the formation of 4he nuclei from hydrogen nuclei (protons) 1H is accompanied by the release of a huge amount of energy. It is believed that this nuclear reaction: 41h = 4he + 2b+ + 2n [simultaneously with 4he, 2 positrons (b +) and 2 neutrinos (n) are formed] serves as the main source of energy for the Sun and other stars similar to it. Thanks to this process, very significant reserves of gas accumulate in the Universe.
Physical and chemical properties . Under normal conditions, gas is a monatomic gas, colorless and odorless. Density 0.17846 g/l, tkip - 268.93°C. G. is the only element that in the liquid state does not solidify at normal pressure, no matter how deeply it is cooled. The lowest pressure for the transition of liquid gas into solid is 2.5 Mn/m2 (25 am), and tmelt is equal to - 272.1°C. Thermal conductivity (at 0°C) 143.8 10-3 W/cm (k. The radius of a hydrogen atom, determined by various methods, ranges from 0.85 to 1.33. About 8 .8 ml G. The primary ionization energy of G. is greater than that of any other element - 39.38 10-13 J (24.58 eV); G. does not have an affinity for electrons. Liquid G., consisting only of 4he, exhibits a number of unique properties (see below).
Until now, attempts to obtain stable chemical compounds of gas have ended in failure (see Inert gases). The existence of the he2+ ion in the discharge has been spectroscopically proven. In 1967, Soviet researchers V.P. Bochin, N.V. Zakurin, and V.K. Kapyshev reported the synthesis of hef+, hef22+, and hef2+ ions in the arc discharge zone due to the reaction of hydrogen with fluorine, with bf3, or with ruf5. According to the calculation, the dissociation energy of the hef+ ion is 2.2 eV.
Receipt and application. In industry, gas is produced from helium-containing natural gases (at present, mainly deposits containing >0.1% gas are exploited). Gas is separated from other gases by the method of deep cooling, taking advantage of the fact that it is more difficult to liquefy than all other gases.
Due to its inertness, hydrocarbons are widely used to create a protective atmosphere during melting, cutting, and welding of active metals. Hydrogen is less electrically conductive than another inert gas, argon, and therefore the electric arc in the gas atmosphere produces higher temperatures, which significantly increases the speed of arc welding. Due to its low density combined with its non-flammability, gas is used to fill stratospheric balloons. The high thermal conductivity of gas, its chemical inertness, and its extremely low ability to enter into a nuclear reaction with neutrons make it possible to use gas for cooling nuclear reactors. Liquid gas is the coldest liquid on Earth and serves as a coolant in various scientific research. One of the methods for determining their absolute age is based on determining the geological content in radioactive minerals (see Geochronology). Due to the fact that nitrogen is very poorly soluble in the blood, it is used as a component of artificial air supplied for breathing to divers (replacing nitrogen with nitrogen prevents the occurrence of decompression sickness). The possibilities of using gas in the atmosphere of a spacecraft cabin are also being studied.
S. S. Berdonosov, V. P. Yakutseni.
Helium is liquid. The relatively weak interaction of gas atoms leads to the fact that it remains gaseous to lower temperatures than any other gas. The maximum temperature below which it can be liquefied (its critical temperature tk) is 5.20 K. Liquid gas is the only non-freezing liquid: at normal pressure (Fig. 1) gas remains liquid at arbitrarily low temperatures and only solidifies at pressures exceeding 2.5 Mn/m2 (25 am).
At a temperature tλ = 2.19 K and normal pressure, liquid gas undergoes a second-order phase transition. G. above this temperature is called He i, below - He ii. At the temperature of the phase transition, an anomalous increase in heat capacity, a break in the curve of the temperature dependence of the gas density, and other characteristic phenomena are observed.
In 1938, P. L. Kapitsa discovered superfluidity in He ii - the ability to flow with virtually no viscosity. An explanation of this phenomenon was given by L. D. Landau (1941) on the basis of quantum mechanical concepts about the nature of thermal motion in liquid gas.
At low temperatures, this movement is described as the existence in liquid gas of elementary excitations - phonons (sound quanta) with energy e = hv (v is the frequency of sound, h is Planck’s constant) and momentum p = e/c (c = 240 m /sec - speed of sound). The number and energy of phonons increase with increasing temperature T. At t > 0.6 K, excitations with high energies (rotons) appear, for which the e(p) dependence is nonlinear. Phonons and rotons have momentum and therefore mass. Relative to 1 cm, this mass determines the density rn so-called. the normal component of liquid gas. At low temperatures, rn tends to zero at T -> 0. The movement of the normal component, like that of an ordinary gas, has a viscous character. The rest of the liquid G., so-called. superfluid component, moves without friction; its density ps = p - pn. At T -> tλ pn -> pr, so that at the λ-point ps becomes zero and superfluidity disappears (He i is an ordinary viscous liquid).
Thus, in liquid gas two movements at different speeds can occur simultaneously.
Based on these concepts, it is possible to explain a number of observed effects: when he ii flows out of a vessel through a narrow capillary, the temperature in the vessel increases, because What flows out is mainly the superfluid component, which does not carry heat with it (the so-called mechanocaloric effect); when a temperature difference is created between the ends of a closed capillary with He ii, movement occurs in it (thermomechanical effect) - the superfluid component moves from the cold end to the hot one and there turns into a normal one, which moves towards, while there is no total flow. Two types of sound can propagate in liquid gas - ordinary and so-called. second sound. When the second sound propagates in places where the normal component is concentrated, a rarefaction of the superfluid component occurs.
All of the above applies to ordinary gas, which consists mainly of the 4he isotope. The rarer isotope 3he has different quantum properties than 4he). Liquid 3he is also a non-freezing liquid (tk = 3.33 K), but does not have superfluidity: the viscosity of 3he increases without limit with decreasing temperature.
Lit.: Keesom V., Helium, trans. from English, M., 1949; Fastovsky V. G., Rovinsky A. E., Petrovsky Yu. V., Inert Gases, M., 1964; Khalatnikov I.M., Introduction to the theory of superfluidity, M., 1965; Smirnov Yu. N., Helium near absolute zero, “Priroda”, 1967, No. 10, p. 70; Yakutseni V.P., Geology of Helium, Leningrad, 1968. See also lit. to Art. Inert gases.
Helium is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, first in the group of noble gases in the periodic table. Its boiling point is the lowest of all elements. After hydrogen, helium is the second lightest and second most abundant element in the observable universe, present at about 24% of the total mass of the elements, more than 12 times the mass of all heavier elements combined. Its abundance is due to the very high nuclear binding energy (per nucleon) of helium-4 relative to the next three elements after helium. This helium-4 binding energy also explains why helium is a product of both nuclear fusion and radioactive decay. Most of the helium in the universe is in the form of helium-4, and is believed to have formed during the Big Bang. Large amounts of new helium are created by nuclear fusion of hydrogen in stars. Helium is named after the Greek god of the sun, Helios. Helium was first discovered as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by Georges Rayet, Captain C.T. Haig, Norman R. Pogson and Lieutenant John Herschel.
This observation was subsequently confirmed by French astronomer Jules Janssen. Janssen is often credited with discovering this element along with Norman Lockyer. Janssen recorded the spectral line of helium during the 1868 solar eclipse, while Lockyer observed the phenomenon from Britain. Lockyer was the first to suggest that this line was associated with a new element, to which he gave the name helium. The formal discovery of the element was made in 1895 by two Swedish chemists, Per Theodor Cleave and Niels Abraham Langlet, who discovered helium coming from the uranium ore kleveite. In 1903, large reserves of helium were discovered in natural gas fields in parts of the United States. Today, the USA is the largest gas supplier. Liquid helium is used in cryogenics (its largest single use, consuming about a quarter of production), particularly in cooling superconducting magnets, with the main commercial use being in MRI scanners. Other industrial uses of helium are as a pressurization and purge gas, as a protective atmosphere for arc welding, and in processes such as crystal growth to make silicon wafers. A well-known but minor use of helium is as a lifting gas for balloons and airships. As with any gas whose density is different from that of air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice. In scientific research, the behavior of the two liquid phases of helium-4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular the property of superfluidity) and to scientists studying phenomena such as superconductivity in matter near absolute zero. On Earth, helium is relatively rare - 5.2 ppm. by volume in the atmosphere. Today, most of the helium present on Earth is created through the natural radioactive decay of heavy radioactive elements (thorium and uranium, although there are other examples), since the alpha particles emitted by such decays are composed of helium-4 nuclei. This radiogenic helium is captured in natural gas in concentrations of up to 7% by volume, from which it is extracted commercially by a low-temperature separation called fractional distillation. Terrestrial helium used to be a non-renewable resource because, once released into the atmosphere, it could easily travel into space, and the element was thought to be increasingly scarce. However, recent research suggests that helium, formed on Earth from radioactive decay, may be collecting in natural gas reserves in larger quantities than expected, in some cases released by volcanic activity.
Story
Scientific discoveries
The first evidence of the existence of helium was made on August 18, 1868. A bright yellow line with a wavelength of 587.49 nanometers was observed in the spectrum of the solar chromosphere. This line was discovered by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. This line was originally thought to be sodium. On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in the spectrum of the Sun, which he called the D3 Fraunhofer line because it was close to the famous D1 and D2 lines of sodium. The scientist concluded that this line was caused by an element of the Sun, unknown on Earth. Lockyer and the English chemist Edward Frankland named the element from the Greek word for sun, ἥλιος (helios). In 1881, Italian physicist Luigi Palmieri first discovered helium on Earth through its D3 spectral line, while analyzing material that was sublimated during the eruption of Mount Vesuvius. On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a range of uraninites with at least 10% rare earth elements) with mineral acids. Ramsay was looking for argon, but after separating the nitrogen and oxygen from the gas produced by the sulfuric acid, he noticed a bright yellow line that matched the D3 line seen in the spectrum of the Sun. These samples were identified as helium by Lockyear and British physicist William Crookes. Helium was independently isolated from kleveite in the same year by chemists Per Theodor Kleve and Abraham Langlet in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight. Helium was also isolated by American geochemist William Francis Hillebrand before Ramsey's discovery, when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed these lines to nitrogen. In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles were helium nuclei by allowing the particles to penetrate the thin glass wall of an evacuated tube and then creating a discharge in the tube to study the spectra of the new gas inside. In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to a temperature of less than one kelvin. He tried to make the gas solid by lowering the temperature further, but failed because helium does not solidify at atmospheric pressure. Onnes's student, Willem Hendrik Keesom, was eventually able to cause 1 cm3 of helium to solidify in 1926 by adding additional external pressure. In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has virtually no viscosity at temperatures near absolute zero, a phenomenon now called superfluidity. This phenomenon is associated with Bose-Einstein condensation. In 1972, the same phenomenon was observed for helium-3, but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff, David M. Lee and Robert C. Richardson. The phenomenon in helium-3 is thought to be due to the pairing of helium-3 fermions to form bosons, analogous to Cooper pairs of electrons that produce superconductivity.
Extraction and Use
After an oil drilling operation in 1903, Dexter, Kansas, produced a gas geyser that did not burn, and Kansas State Geologist, Erasmus Haworth, collected samples of the escaping gas and took them to the University of Kansas at Lawrence, where, with the help of chemists Hamilton Cady and David McFarland, he found that the gas consisted of 72% nitrogen, 15% methane (the flammable percentage with only enough oxygen), 1% hydrogen and 12% unidentifiable gas. Upon further analysis, Cady and McFarland found that 1.84% of the gas sample was helium. This showed that, despite its general rarity on Earth, helium was concentrated in large quantities beneath the American Great Plains, available for extraction as a byproduct of natural gas. This allowed the United States to become the world's leading supplier of helium. Following a suggestion by Sir Richard Threlfall, the United States Navy sponsored three small experimental helium plants during the First World War. The goal was to supply barrage balloons with a non-flammable gas lighter than air. During this program, 5,700 m3 (200,000 cu ft) of 92% helium was produced, although less than one cubic meter of this gas had previously been produced. Some of this gas was used in the world's first helium airship, the US Navy's C-7, which made its maiden voyage from Hampton Roads, Virginia, to Bolling Field in Washington, D.C., on December 1, 1921, nearly two years before it was built. the first helium-filled rigid airship in September 1923 at the Shenandoah plant. Although the extraction process using low-temperature gas liquefaction was not developed at the time, production continued during World War I. Helium was primarily used as a lifting gas in lighter-than-air aircraft. During World War II, the demand for helium as a lifting gas and for shielded arc welding increased. The helium mass spectrometer was also of great importance in the Manhattan Project (the code name for the work to create the first atomic bomb in the United States during the Second World War). The United States government established the National Helium Reserve in 1925 in Amarillo, Texas, for the purpose of supplying military airships in times of war and commercial airships in times of peace. Because of the Helium Control Act (1927), which prohibited the export of rare helium, the production of which the United States then had a monopoly on, coupled with the prohibitive cost of gas, the Hindenburg, like all German Zeppelins, was forced to use hydrogen as a lift gas. The market for helium was suppressed after World War II, but supplies were expanded in the 1950s to provide liquid helium as a coolant to create oxyhydrogen rocket fuel (among other uses) during the Space Race and the Cold War. Helium use in the United States in 1965 was more than eight times peak wartime consumption. Following the Helium Act Amendments of 1960 (Public Law 86-777), the United States Bureau established five private plants to recover helium from natural gas. For this helium conservation program, the Bureau constructed a 425-mile (684-kilometer) pipeline from Bushton, Kansas, to connect these plants to the government's partially depleted Cliffside gas field near Amarillo, Texas. This helium-nitrogen mixture was injected and stored in the Cliffside gas field until it was needed, during which time it was further purified. By 1995, a billion cubic meters of gas had been collected and the reserve was $1.4 billion in debt, prompting the United States Congress to eliminate the reserve in 1996. The Helium Privatization Act of 1996 (Public Law 104-273) forces the United States Department of the Interior to release the reserve and begin sales in 2005. Helium produced between 1930 and 1945 was approximately 98.3% pure (2% nitrogen), sufficient for airships. In 1945, small amounts of 99.9% helium were produced for welding. By 1949, commercial quantities of 99.95% Class A helium were available. For many years, the United States produced more than 90% of the world's commercially used helium, with mining plants in Canada, Poland, Russia and other countries producing the rest. In the mid-1990s, a new plant in Argeve, Algeria, began operating, producing 17 million cubic meters (600 million cubic feet of helium), with enough production to cover all of Europe's needs. Meanwhile, by 2000, helium consumption in the United States increased to more than 15 million kg per year. In 2004-2006, additional plants were built in Ras Laffan, Qatar and Skikda, Algeria. Algeria quickly became the second leading producer of helium. During this time, both helium consumption and helium production costs increased. From 2002 to 2007 Helium prices have doubled. As of 2012, the United States National Helium Reserve accounted for 30 percent of the world's helium reserves. The reserve is expected to run out in 2018. Despite this, proposed legislation in the United States Senate would allow the reserve to continue selling gas. Other large helium reserves were located in the Hugoton State of Kansas, USA, and nearby gas fields in Kansas, as well as in the Texas and Oklahoma salients. New helium plants were due to open in 2012 in Qatar, Russia and the US state of Wyoming, but were not expected to ease the shortage. In 2013, construction began on the world's largest helium plant in Qatar. 2014 was widely considered a year of oversupply in the helium business, after years of shortages.
Characteristics
Helium atom
Helium in quantum mechanics
From a quantum mechanics perspective, helium is the second simplest atom to model, following the hydrogen atom. Helium consists of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons. As in Newtonian mechanics, no system consisting of more than two particles can be solved using a precise analytical mathematical approach, and helium is no exception. Thus, numerical mathematical methods are required, even to solve a system consisting of one nucleus and two electrons. Such computational chemistry techniques have been used to create a quantum mechanical picture of helium's electronic binding that is accurate to less than 2% of the correct value across multiple computational steps. Such models show that each electron in helium partially shields one nucleus from the other, so that the effective nuclear charge Z that each electron sees is about 1.69 units, rather than the 2 charge of a classical "naked" helium nucleus.
Relative stability of the helium-4 nucleus and electron shell
The nucleus of a helium-4 atom is identical to an alpha particle. High-energy electron scattering experiments show that its charge decreases exponentially from a maximum at the central point, just like the charge density of helium's own electron cloud. This symmetry reflects similar underlying physics: a pair of neutrons and a pair of protons in a helium nucleus obey the same quantum mechanical rules as a pair of helium electrons (although the nuclear particles are subject to a different nuclear binding potential), so that all of these fermions completely occupy the 1s orbitals in the pairs , and neither of them has orbital momentum, and each of them cancels the other’s own spin. Adding any other of these particles would require angular momentum and release substantially less energy (in fact, no nucleus with five nucleons is stable). So this scheme is energetically extremely stable for all these particles, and this stability explains many important facts about helium in nature. For example, the stability and low energy state of the electron cloud in helium explains the chemical inertness of the element, as well as the lack of interaction of helium atoms with each other, creating the lowest melting and boiling points of all elements. Likewise, the special energetic stability of the helium-4 nucleus, created by similar effects, explains the ease of production of helium-4 in atomic reactions that involve either the release of heavy metals or their synthesis. Some stable helium-3 (2 protons and 1 neutron) is produced in fusion reactions from hydrogen, but this amount is very small compared to the highly sensitive energy of helium-4. The unusual stability of the helium-4 nucleus is also important cosmologically: it explains the fact that in the first few minutes after the Big Bang, during the creation of the "mash of free protons and neutrons" that were originally created in a ratio of about 6:1, cooled to such a to the extent that nuclear bonding became possible, almost all of the first compound atomic nuclei formed were helium-4 nuclei. helium-4 binding was so tight that helium-4 production consumed almost all of the free neutrons within minutes before they could be beta-decayed, leaving little to form heavier atoms such as lithium, beryllium or boron . The nuclear binding of helium-4 per nucleon is stronger than that of any of these elements, and thus, when helium was formed, there was no energetic drive to create elements 3, 4 and 5. It was of little energetic benefit for helium to fuse into the next element with less energy per nucleon, carbon. However, due to the lack of intermediate elements, this process requires three helium nuclei striking each other almost simultaneously. Thus, in the minutes after the Big Bang, there was no time for significant amounts of carbon to form before the early expanding Universe cooled to a temperature and pressure at which fusion of helium with carbon would be impossible. Because of this, the early universe had a hydrogen/helium ratio similar to today's (3 parts hydrogen to 1 part helium-4 by mass), with almost all of the neutrons in the universe captured by helium-4. All heavier elements (including elements needed for rocky planets like Earth and for carbon-based or other life forms) were thus created after the Big Bang in stars that were hot enough to fuse helium itself. All elements except hydrogen and helium today make up only 2% of the mass of atomic matter in the Universe. Helium-4, by contrast, makes up about 23% of the universe's ordinary matter—almost all the ordinary matter that is not hydrogen.
Gas and plasma phases
Helium is the second least reactive noble gas after neon and therefore the second least reactive of all the elements. It is inert and monoatomic under all standard conditions. Because of helium's relatively low molar (atomic) mass, its thermal conductivity, specific heat capacity, and speed of sound in the gas phase are greater than those of any other gas except hydrogen. For these reasons and because of the small size of monatomic helium molecules, helium diffuses through solid particles at a speed three times the speed of air and about 65% of the speed of hydrogen. Helium is the least water-soluble monatomic gas and one of the less water-soluble gases (CF4, SF6 and C4F8 have lower molar solubilities: 0.3802, 0.4394 and 0.2372 x2/10-5 respectively versus 0.70797 x2/10-5 5 for helium), in addition, the refractive index of helium is closer to unity than the refractive index of any other gas. Helium has a negative Joule-Thomson coefficient at normal ambient temperatures, which means it heats up when it is allowed to expand freely. Just below its Joule-Thomson inversion temperature (about 32 to 50 K at 1 atmosphere), helium cools as it expands freely. Once supercooled below this temperature, the helium can be liquefied by refrigeration. Most extraterrestrial helium is in a plasma state and has properties completely different from those of atomic helium. In plasma, helium's electrons are not bound to its nucleus, resulting in very high electrical conductivity even when the gas is only partially ionized. Charged particles are strongly influenced by magnetic and electric fields. For example, in the solar wind, along with ionized hydrogen, the particles interact with the Earth's magnetosphere, leading to Birkeland currents and aurora.
Liquid helium
Unlike any other element, helium will remain liquid to absolute zero at normal pressures. This is a direct influence of quantum mechanics: in particular, the zero point energy of the system is too high to allow freezing to occur. Solid helium requires a temperature of 1-1.5 K (about -272 °C or -457 °F) at a pressure of about 25 bar (2.5 MPa). It is often difficult to distinguish solid from liquid helium because the refractive index of the two phases is almost the same. The solid has a distinct melting point and a crystalline structure, but it is highly compressible; applying pressure in the laboratory can reduce its volume by more than 30%. With a bulk modulus of about 27 MPa, helium is 100 times more compressible than water. Solid helium has a density of 0.214 ± 0.006 g/cm3 at 1.15 K and 66 atm; the predicted density at 0 K and 25 bar (2.5 MPa) is 0.187 ± 0.009 g/cm3. At higher temperatures, helium will solidify with sufficient pressure. At room temperature, this requires about 114,000 atm.
Helium state I
Below its boiling point of 4.22 kelvin and above its lambda point of 2.1768 kelvin, the isotopic helium-4 exists in a normal colorless liquid state called helium I. Like other cryogenic liquids, helium I boils when it is heated and contracts when his temperature decreases. However, below the lambda point, helium does not boil and it expands as the temperature drops further. Helium I has a gaseous refractive index of 1.026, making its surface so difficult to view that pop-up polystyrene foams are often used to view its surface. This colorless liquid has a very low viscosity and a density of 0.145-0.125 g/ml (about 0-4 K), which is only one-fourth of the value expected from classical physics. Quantum mechanics is needed to explain this property, and so both states of liquid helium (helium I and helium II) are called quantum liquids, meaning that they exhibit atomic properties on a macroscopic scale. This may be due to the fact that helium's boiling point is so close to absolute zero that it prevents random molecular motion (thermal energy) from masking its atomic properties.
Helium state II
Liquid helium below its lambda point (called helium II) has very unusual characteristics. Due to its high thermal conductivity, when it boils, it does not bubble but evaporates directly from the surface. Helium-3 also has a superfluid phase, but only at much lower temperatures; as a result, little is known about the properties of this isotope. Helium II is a superfluid liquid and a quantum mechanical state with strange properties. For example, when it flows through capillaries 10-7 to 10-8 m thick, it has no measurable viscosity. However, when measurements were taken between two moving disks, a viscosity comparable to that of helium gas was observed. The present theory explains this using a two-fluid model for helium II. In this model, liquid helium below the lambda point is considered to contain a portion of ground-state helium atoms that are superfluid and flow with zero viscosity, and a portion of excited-state helium atoms that behave like an ordinary liquid. In the gushing effect, a chamber is constructed that is connected to the helium II reservoir by a sintered disk through which superfluid helium easily flows, but through which non-superfluid helium cannot pass. If the inside of the container heats up, the superfluid helium changes to non-superfluid helium. To maintain an equilibrium proportion of superfluid helium, superfluid helium flows and increases pressure, causing liquid to release from the container. The thermal conductivity of helium II is greater than that of any other known substance, a million times greater than that of helium I and several hundred times greater than that of copper. This is due to the fact that thermal conduction occurs due to an exceptional quantum mechanism. Most materials that conduct heat have a valence band of free electrons that serve to transfer heat. Helium II does not have such a valence band, but nevertheless conducts heat well. Heat flow is determined by equations that are similar to the wave equation used to characterize the propagation of sound in air. When exposed to heat, it travels at 20 meters per second at 1.8 K through Helium II in the form of waves in a phenomenon known as second sound. Helium II also has a creeping effect. When a surface passes through a Helium II level, Helium II moves across the surface, against gravity. Helium II will exit the unsealed container, sliding down the sides until it reaches a warmer area where it will evaporate. It moves in a 30 nm thick film regardless of the surface material. This film is called Rollin film in honor of the scientist who first characterized this quality, Bernard W. Rollin. As a result of this "creeping" behavior and Helium II's ability to quickly flow through tiny holes, it is very difficult to confine liquid helium. Unless the container is carefully constructed, Helium II will creep along the surface and through the valves until it reaches a warmer area, where it will evaporate. Waves propagating through a Rollin film are governed by the same equation as gravitational waves in shallow water, but instead of gravity, the restoring force is the van der Waals force. These waves are known as third sound.
Isotopes
There are nine known isotopes of helium, but only helium-3 and helium-4 are stable. In the Earth's atmosphere, there is one 3He atom per million 4He atoms. Unlike most elements, the isotopic abundance of helium varies greatly in origin due to different formation processes. The most common isotope, helium-4, is produced on Earth through the alpha decay of heavier radioactive elements; the resulting alpha particles are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its nucleons are arranged in complete shells. It was also formed in huge quantities in big bang nucleosynthesis. Helium-3 is present on Earth only in trace amounts; Most helium-3 has been present since Earth's formation, although some ends up on Earth captured in cosmic dust. Trace amounts of helium are also produced by tritium beta decay. Rocks in the Earth's crust have isotopic ratios that vary by a factor of ten, and these ratios can be used to study the origins of rocks and the composition of the Earth's mantle. 3He is much more common in stars as a product of nuclear fusion. Thus, in the interstellar medium the ratio of 3He to 4He is approximately 100 times higher than on Earth. Extraplanetary material such as lunar and asteroidal regolith has trace amounts of helium-3 from bombardment by solar winds. The Moon's surface contains helium-3 in concentrations on the order of 10 ppm, much higher than the approximately 5 ppm found in the Earth's atmosphere. A number of scientists, starting with Gerald Kulcinski in 1986, have proposed exploring the moon, collecting lunar regolith, and using helium-3 for fusion. Liquid helium-4 can be cooled to about 1 kelvin using evaporative cooling in a pot that reaches 1 K. Similar cooling of lower boiling point helium-3 can reach about 0.2 kelvin in a helium-3 refrigerator. Equal mixtures of liquid 3He and 4He with temperatures below 0.8 K separate into two immiscible phases due to their dissimilarity (they have different quantum statistics: helium-4 atoms are bosons, while helium-3 atoms are fermions). In refrigeration machines operating on a mixture of cryogenic substances, this immiscibility is used to achieve temperatures of several millikelvins. It is possible to produce exotic isotopes of helium that quickly decay into other substances. The shortest-lived heavy isotope of helium is helium-5, with a half-life of 7.6×10-22 s. Helium-6 decays by emitting a beta particle and has a half-life of 0.8 seconds. Helium-7 also emits a beta particle as well as a gamma ray. Helium-7 and helium-8 are formed in some nuclear reactions. Helium-6 and helium-8 are known to have a nuclear halo.
Helium compounds
Helium has a valency of 0 and is chemically inactive under all normal conditions. Helium is an electrical insulator unless it is ionized. Like other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge at a voltage below its ionization potential. Helium can form unstable compounds known as excimers with tungsten, iodine, fluorine, sulfur, and phosphorus when it is subjected to glow discharge, electron bombardment, or reduced to plasma by other means. In this way the molecular compounds HeNe, HgHe10 and WHe2 and the molecular ions He+2, He2+2, HeH+ and HeD+ were created. HeH+ is also stable in its ground state, but is extremely reactive - it is the strongest Brønsted acid, and therefore can only exist in isolation, as it will protonate any molecule or protianion it comes into contact with. This method also created the neutral He2 molecule, which has a large number of band systems, and HgHe, which appears to be held together only by polarization forces. Van der Waals helium compounds can also form with cryogenic helium gas and atoms of some other substance, such as LiHe and He2. It is theoretically possible that there are other true compounds, such as helium fluorohydride (HHeF), which would be similar to HArF discovered in 2000. Calculations show that two new compounds containing a helium-oxygen bond may be stable. The two new molecular species predicted using the theory, CsFHeO and N(CH3)4FHeO, are derivatives of the metastable FHeO anion first proposed in 2005 by a group in Taiwan. If this is confirmed by experiment, the only remaining element with no known stable compounds will be neon. Helium atoms were inserted into molecules of hollow carbon frameworks (fullerenes) by heating under high pressure. The created endohedral fullerene molecules are stable at high temperatures. When chemical derivatives of these fullerenes are formed, helium remains inside. If helium-3 is used, it can be easily observed using helium nuclear magnetic resonance spectroscopy. Many fullerenes containing helium-3 have been reported. Although helium atoms are not linked by covalent or ionic bonds, these substances have certain properties and a certain composition, like all stoichiometric chemical compounds. At high pressures, helium can form compounds with various other elements. Crystals of helium-nitrogen clathrate (He(N2)11) were grown at room temperature at pressures of ca. 10 GPa in a high pressure chamber with diamond anvils. The Na2He insulating electrolyte has been shown to be thermodynamically stable at pressures above 113 GPa. It has a fluorite structure.
Origin and production
Natural abundance
Although helium is rare on Earth, it is the second most abundant element in the known Universe (after hydrogen), accounting for 23% of its baryon mass. The vast majority of helium was formed by Big Bang nucleosynthesis one to three minutes after the Big Bang. Thus, measurements of its abundance contribute to cosmological models. In stars, helium is formed by the nuclear fusion of hydrogen in proton-proton chain reactions and the CNO cycle, part of stellar nucleosynthesis. In the Earth's atmosphere, the concentration of helium by volume is only 5.2 parts per million. The concentration is low and fairly constant despite the continuous production of new helium, because most of the helium in Earth's atmosphere enters space through several processes. In the earth's heterosphere, part of the upper atmosphere, helium and other lighter gases are the most abundant elements. Most of the helium on Earth is the result of radioactive decay. Helium is found in large quantities in uranium and thorium minerals, including kleveite, resin, carnotite and monazite, because they release alpha particles (helium nuclei, He2+), with which electrons immediately bind as soon as the particle is stopped by a stone. Thus, about 3000 metric tons of helium are generated throughout the lithosphere. In the earth's crust, the concentration of helium is 8 parts per billion. In seawater the concentration is only 4 parts per trillion. Small amounts of helium are also present in mineral springs, volcanic gas and meteoric iron. Because helium is trapped in the ground under conditions that also trap natural gas, the largest natural concentrations of helium on the planet are found in natural gas, from which most commercial helium is extracted. Helium concentrations vary widely, from a few ppm to over 7% in a small gas field in San Juan County, New Mexico. As of 2011, global helium reserves were estimated at 40 billion cubic meters, with a quarter of these reserves located in the South Pars/North Dome Gas-Condensate field, jointly owned by Qatar and Iran. In 2015 and 2016, more probable reserves were announced in the North American Rocky Mountains and East Africa.
Modern production and distribution
For large-scale use, helium is extracted by fractional distillation from natural gas, which can contain up to 7% helium. Because helium has a lower boiling point than any other element, low temperature and high pressure are used to liquefy almost all other gases (mainly nitrogen and methane). The resulting raw helium gas is purified by successive steps of lowering the temperature, at which time almost all of the remaining nitrogen and other gases are precipitated from the gas mixture. Activated carbon is used as the final purification step, typically producing 99.995% pure Class A helium. The main impurity in class A helium is neon. At the final stage of production, most of the helium produced is liquefied through a cryogenic process. This is essential for applications requiring liquid helium and also allows helium suppliers to reduce the cost of transporting helium over long distances, as the largest liquid helium containers have more than five times the capacity of the largest gas helium trailers. In 2008, approximately 169 million standard cubic meters of helium were extracted from natural gas or withdrawn from helium reserves, approximately 78% from the United States, 10% from Algeria and most of the remainder from Russia, Poland and Qatar. By 2013, increased helium production in Qatar (RasGas under Air Liquide) increased Qatar's share of global helium production to 25% and made the country the second largest helium exporter after the United States. It is estimated that about 54 billion cubic feet (1.5×109 m3) of helium were discovered in Tanzania in 2016. In the United States, most helium is extracted from natural gas in Hugoton and nearby gas fields in Kansas, Oklahoma, and the Panhandle field in Texas. Much of this gas was once piped to the National Helium Reserve, but the reserve has been depleted and sold off since 2005, and is expected to be largely depleted by 2021, according to the Responsible Helium and Stewardship Act. passed in October 2013 (HR 527). Diffusion of raw natural gas through special semi-permeable membranes and other barriers is another way to recover and purify helium. In 1996, the United States discovered reserves of helium in such gas well complexes, about 147 billion standard cubic feet (4.2 billion SCM). At the rate of use at the time (72 million SCM per year in the US), there would be enough helium to last for about 58 years in the US, and less than that (perhaps 80% of the time) in the world, but factors affecting the economy and processing, affect effective reserve indicators. Helium must be extracted from natural gas because it is only a fraction of the fraction of neon in the air, but the demand for it is much greater. It is estimated that if all neon products were converted to store helium, 0.1% of the world's helium demand would be met. Likewise, only 1% of the world's helium needs can be met by reinstalling all air distillation plants. Helium can be synthesized by bombarding lithium or boron with high-speed protons or by bombarding lithium with deuterons, but these processes are completely uneconomical. Helium is commercially available in either liquid or gaseous form. As a liquid, it can be supplied in small insulated containers called dewars, which hold up to 1,000 liters of helium, or in large ISO containers, which have a nominal capacity of up to 42 m3 (about 11,000 US gallons). In gaseous form, small quantities of helium are sold in high-pressure cylinders holding up to 8 m3 (about 282 standard cubic feet) of helium, while large quantities of high-pressure gas are supplied in tubular trailers that have a capacity of 4,860 m3 (about 172,000 standard cubic feet) of helium. cubic feet).
Helium safety protection
According to helium conservation advocates, such as Nobel Prize-winning physicist Robert Coleman Richardson, writing in 2010, the free market price of helium has contributed to its "wasteful" use (such as for helium balloons). In the 2000s, prices were lowered by a decision by the US Congress to sell large reserves of helium in the country by 2015. The price would have to be multiplied by 20 to eliminate excessive helium depletion, Richardson said. In their book The Future of Helium as a Natural Resource (Routledge, 2012), Nuttall, Clarke & Glowacki (2012) also proposed the creation of an International Helium Agency (IHA) to create a sustainable market for this precious commodity.
Areas of use
While balloons are perhaps the best known way to use helium, they make up a small portion of all helium use. Helium is used for many purposes that require some of its unique properties, such as low boiling point, low density, low solubility, high thermal conductivity, or inertness. Of the 2014 total world helium production, about 32 million kg (180 million standard cubic meters) of helium per year, the largest use (about 32% of the 2014 total) is in cryogenic applications, most of which involve cooling superconducting magnets in medical MRI scanners and NMR spectrometers. Other major applications were pressurization and purge systems, welding, controlled atmosphere maintenance and leak detection. Other uses by category accounted for relatively small fractions.
Controlled Atmospheres
Helium is used as a shielding gas in the growing of silicon and germanium crystals, in the production of titanium and zirconium, and in gas chromatography because it is inert. Due to its inertness, thermal and calorically perfect nature, high speed of sound and high heat capacity ratio, it is also useful in supersonic wind tunnels and impulse plants.
Gas tungsten arc welding
Helium is used as a shielding gas in arc welding processes on materials that are contaminated and weakened by air or nitrogen at welding temperatures. Gas tungsten arc welding uses a range of inert shielding gases, but uses helium instead of cheap argon, especially for higher thermal conductivity welding materials such as aluminum or copper.
Less common uses
Industrial Leak Detection
One industrial use of helium is leak detection. Because helium diffuses through solids three times faster than air, it is used as a tracer gas to detect leaks in high-vacuum equipment (such as cryogenic tanks) and high-pressure containers. The test substance is placed in a chamber, which is then evacuated and filled with helium. Helium that passes through a leak is detected by a sensitive device (helium mass spectrometer) even at leak rates of 10-9 mbar l/s (10-10 Pa m3/s). The measurement procedure is usually performed automatically and is called the integral helium test. The simple procedure is to fill the test object with helium and search for leaks manually using a hand-held device. Helium leakage through cracks should not be confused with gas penetration through bulk material. While helium has documented permeation constants (thus estimated permeation rates) through glasses, ceramics, and synthetic materials, noble gases such as helium will not penetrate most large metals.
Flying
Because helium is lighter than air, airships and balloons are pumped with this gas to lift them into the air. While hydrogen gas is more able to adhere to a surface and penetrates the membrane at a slower rate, helium has the advantage of being non-flammable and truly fire retardant. Another minor use of helium is in rockets, where helium is used as a cushion of air to replace fuel and oxidizers in storage tanks and to condense hydrogen and oxygen to produce rocket fuel. It is also used to purify fuel and oxidizer from ground support equipment prior to launch and to pre-cool liquid hydrogen on spacecraft. For example, the Saturn V rocket used in the Apollo program required about 370,000 m3 (13 million cubic feet) of helium to launch.
Minor commercial and recreational uses
Helium as a breathing gas does not have any narcotic properties, so helium mixtures such as Trimix, Heliox and Heliair are used for deep diving to reduce the effects of anesthesia, which worsen with increasing depth. As pressure increases at depth, the density of the breathing gas also increases, and the low molecular weight of helium significantly reduces the breathing effort, reducing the density of the mixture. This reduces the number of Reynolds flows, which results in less turbulent flow and more laminar flow, which requires less work to breathe. At depths below 150 meters (490 feet), divers inhaling helium-oxygen mixtures begin to experience tremors and decreased psychomotor function, a nervous syndrome caused by high blood pressure. To some extent, this effect may be facilitated by the addition of some narcotic gases, such as hydrogen or nitrogen, to the helium-oxygen mixture. Helium-neon lasers, a type of low-power gas laser that produces a red beam, had a variety of practical applications, including bar code readers and laser pointers, before they were almost universally replaced by cheaper diode lasers. Because of its inertness and high thermal conductivity, neutron transparency, and lack of formation of radioactive isotopes under reactor conditions, helium is used as a coolant in some gas-cooled nuclear reactors. Helium mixed with a heavier gas such as xenon is useful for thermoacoustic cooling due to the resulting high heat capacity coefficient and low Prandtl number. Helium's inertia has environmental advantages over traditional refrigeration systems, which contribute to ozone depletion or global warming. Helium is also used in some hard drives.
Scientific Applications
The use of helium reduces the distorting effects of temperature changes in the space between lenses in some telescopes due to its extremely low refractive index. This method is especially used in solar telescopes, where the vacuum insulated telescope tube would be too heavy. Helium is a widely used carrier gas for gas chromatography. The age of rocks and minerals containing uranium and thorium can be estimated by measuring helium levels in a process known as helium dating. Helium at low temperatures is used in cryogenics and some cryogenics applications. As examples of such applications, liquid helium is used to cool some metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging. The Large Hadron Collider at CERN uses 96 metric tons of liquid helium to maintain a temperature of 1.9 kelvin.
Inhalation and safety
Effects
Neutral helium is non-toxic under standard conditions, does not play any biological role, and is found in trace amounts in human blood. The speed of sound in helium is almost three times the speed of sound in air. Because the fundamental frequency of a gas-filled cavity is proportional to the speed of sound in the gas, when helium is inhaled, there is a corresponding increase in the resonant frequencies of the vocal tract. The fundamental frequency (sometimes called tone) does not change, as this occurs through direct vibration of the vocal folds, which does not change. However, higher resonant frequencies cause a change in timbre, resulting in a thin, duck-like sound. The opposite effect, lowering resonant frequencies, can be obtained by inhaling a dense gas such as sulfur hexafluoride or xenon.
Dangers
Inhaling excess amounts of helium can be dangerous because helium is a simple asphyxiant that displaces the oxygen needed for normal breathing. Deaths have been reported, including a young man who suffocated in Vancouver in 2003 and two adults who suffocated in South Florida in 2006. In 1998, an Australian girl (her age unknown) from Victoria fell unconscious and temporarily turned blue after inhaling the entire contents of a helium tank. Inhaling helium directly from pressurized cylinders or even cylinder filling valves is extremely dangerous, as the high flow rates and pressures can cause barotrauma, fatal damage to lung tissue. Death caused by helium is rare. The first reported case was that of a 15-year-old Texas girl who died in 1998 from helium inhalation at a friend's party. In the United States, only two deaths were reported between 2000 and 2004, including a man who died in North Carolina from barotrauma in 2002. A young man suffocated in Vancouver in 2003, and a 27-year-old man in Australia had an embolism after inhaling gas from a cylinder in 2000. Since then, two adults suffocated in South Florida in 2006, several cases were reported in 2009 and 2010, one involving a California youth found with a bag over his head attached to a helium tank, and another involving a teenager in Northern Ireland. , died of suffocation. In Eagle Point, Oregon, a teenage girl died in 2012 from barotrauma at a party. A Michigan girl died of hypoxia later that year. On February 4, 2015, it was revealed that on January 28, during a taping of Japanese girl group 3B Junior's television show, a 12-year-old member of the group (whose name was kept secret) suffered an embolism, lost consciousness and fell into a coma as a result of air bubbles blocking blood flow in the brain. after inhaling huge amounts of helium. The incident was not made public until the following week. TV Asahi staff held an emergency press conference to report that the girl had been taken to the hospital and that she was showing signs of recovery, such as eye and limb movement, but her consciousness had not yet been fully recovered. The police launched an investigation due to the neglect of security measures. Safety concerns for cryogenic helium are similar to those for liquid nitrogen; its extremely low temperatures can cause cold burns, and its liquid-to-gas expansion ratio can cause explosions unless pressure relief devices are installed. Containers of helium gas at 5-10 K should be treated as if they contained liquid helium due to the rapid and significant thermal expansion that occurs when helium gas at less than 10 K is warmed to room temperature. At high pressures (more than about 20 atm or two MPa), a mixture of helium and oxygen (heliox) can lead to high pressure nervous syndrome, a kind of reverse anesthetic effect; adding a small amount of nitrogen to the mixture may alleviate the problem.
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Rayet, G. (1868) "Analyse spectral des protuberances observées, pendant l"éclipse totale de Soleil visible le 18 août 1868, à la presqu"île de Malacca" (Spectral analysis of the protuberances observed during the total solar eclipse, seen on 18 August 1868, from the Malacca peninsula), Comptes rendus…, 67: 757–759. From p. 758: "... je vis immédiatement une série de neuf lignes brillantes qui... me semblent devoir être assimilées aux lignes principales du spectre solaire, B, D, E, b, une ligne inconnue, F, et deux lignes du groupe G." (... I saw immediately a series of nine bright lines that... seemed to me should be classified as the principal lines of the solar spectrum, B, D, E, b, an unknown line, F, and two lines of the group G.
Helium is a truly noble gas. It has not yet been possible to force him into any reaction. The helium molecule is monatomic.
In terms of lightness, this gas is second only to hydrogen; air is 7.25 times heavier than helium.
Helium is almost insoluble in water and other liquids. And in the same way, not a single substance dissolves noticeably in liquid helium.
Solid helium cannot be obtained at any temperature unless the pressure is increased.
In the history of the discovery, research and application of this element, the names of many prominent physicists and chemists from different countries can be found. They were interested in helium and worked with helium: Jansen (France), Lockyer, Ramsay, Crookes, Rutherford (England), Palmieri (Italy), Keesom, Kamerlingh-Onnes (Holland), Feynman, Onsager (USA), Kapitza, Kikoin, Landau ( Soviet Union) and many other prominent scientists.
The unique appearance of the helium atom is determined by the combination of two amazing natural structures - absolute champions in compactness and strength. In the core of helium, helium-4, both intranuclear shells are saturated - both proton and neutron. The electronic doublet framing this core is also saturated. These designs hold the key to understanding the properties of helium. This is the source of its phenomenal chemical inertness and the record small size of its atom.
The role of the nucleus of the helium atom - the alpha particle - is enormous in the history of the formation and development of nuclear physics. If you remember, it was the study of alpha particle scattering that led Rutherford to the discovery of the atomic nucleus. By bombarding nitrogen with alpha particles, the interconversion of elements was accomplished for the first time - something that many generations of alchemists had dreamed about for centuries. True, in this reaction it was not mercury that turned into gold, but nitrogen into oxygen, but this is almost as difficult to do. The same alpha particles were involved in the discovery of the neutron and the production of the first artificial isotope. Later, curium, berkelium, californium, and mendelevium were synthesized using alpha particles.
We have listed these facts for only one purpose - to show that element No. 2 is a very unusual element.
Terrestrial helium
Helium is an unusual element, and its history is unusual. It was discovered in the solar atmosphere 13 years earlier than on Earth. More precisely, a bright yellow D line was discovered in the spectrum of the solar corona, and what was hidden behind it became reliably known only after helium was extracted from earthly minerals containing radioactive elements.
Helium in the Sun was discovered by the Frenchman J. Jansen, who carried out his observations in India on August 19, 1868, and the Englishman J.H. Lockyer - October 20 of the same year. Letters from both scientists arrived in Paris on the same day and were read at a meeting of the Paris Academy of Sciences on October 26, with an interval of several minutes. Academicians, amazed by such a strange coincidence, decided to knock out a gold medal in honor of this event.
In 1881, the Italian scientist Palmieri reported the discovery of helium in volcanic gases. However, his message, later confirmed, was taken seriously by few scientists. Terrestrial helium was discovered again by Ramsay in 1895.
There are 29 isotopes in the earth's crust, the radioactive decay of which produces alpha particles - highly active, high-energy nuclei of helium atoms.
Basically, terrestrial helium is formed during the radioactive decay of uranium-238, uranium-235, thorium and unstable products of their decay. Incomparably smaller amounts of helium are produced by the slow decay of samarium-147 and bismuth. All these elements generate only the heavy isotope of helium - 4 He, whose atoms can be considered as the remains of alpha particles buried in a shell of two paired electrons - in an electron doublet. In early geological periods, there were probably other naturally radioactive series of elements that had already disappeared from the face of the Earth, saturating the planet with helium. One of them was the now artificially recreated neptunium series.
By the amount of helium locked in a rock or mineral, one can judge its absolute age. These measurements are based on the laws of radioactive decay: for example, half of uranium-238 turns into helium and lead in 4.52 billion years.
Helium accumulates slowly in the earth's crust. One ton of granite containing 2 g of uranium and 10 g of thorium produces only 0.09 mg of helium over a million years - half a cubic centimeter. The very few minerals rich in uranium and thorium have quite high helium contents—several cubic centimeters of helium per gram. However, the share of these minerals in natural helium production is close to zero, since they are very rare.
Natural compounds that contain alpha active isotopes are only a primary source, but not a raw material for the industrial production of helium. True, some minerals with a dense structure - native metals, magnetite, garnet, apatite, zircon and others - firmly retain the helium contained in them. However, over time, most minerals undergo processes of weathering, recrystallization, etc., and helium leaves them.
Helium bubbles released from crystalline structures set off on a journey across the earth's crust. A very small part of them dissolves in groundwater. To form more or less concentrated helium solutions, special conditions are needed, primarily high pressures. Another part of the wandering helium escapes into the atmosphere through the pores and cracks of minerals. The remaining gas molecules fall into underground traps, where they accumulate for tens or hundreds of millions of years. The traps are layers of loose rocks, the voids of which are filled with gas. The bed for such gas reservoirs is usually water and oil, and on top they are covered by gas-impermeable strata of dense rocks.
Since other gases (mainly methane, nitrogen, carbon dioxide) also travel in the earth’s crust, and in much larger quantities, pure helium accumulations do not exist. Helium is present in natural gases as a minor impurity. Its content does not exceed thousandths, hundredths, and rarely tenths of a percent. Large (1.5...10%) helium content of methane-nitrogen deposits is an extremely rare phenomenon.
Natural gases turned out to be practically the only source of raw materials for the industrial production of helium. To separate it from other gases, the exceptional volatility of helium, associated with its low liquefaction temperature, is used. After all other components of the natural gas have condensed during deep cooling, the helium gas is pumped out. It is then cleaned of impurities. The purity of factory helium reaches 99.995%.
Helium reserves on Earth are estimated at 5·10 14 m 3 ; judging by calculations, tens of times more of it was formed in the earth’s crust over 2 billion years. This discrepancy between theory and practice is quite understandable. Helium is a light gas and, like hydrogen (albeit slower), does not escape from the atmosphere into outer space. Probably, during the existence of the Earth, the helium of our planet was repeatedly renewed - the old one evaporated into space, and instead of it, fresh helium entered the atmosphere - “exhaled” by the Earth.
There is at least 200 thousand times more helium in the lithosphere than in the atmosphere; Even more potential helium is stored in the “womb” of the Earth - in alpha active elements. But the total content of this element in the Earth and atmosphere is small. Helium is a rare and diffuse gas. There is only 0.003 mg of helium per 1 kg of earthly material, and its content in the air is 0.00052 percent by volume. Such a low concentration does not yet allow for economical extraction of helium from the air.
Helium in the Universe
The interior and atmosphere of our planet are poor in helium. But this does not mean that there is little of it everywhere in the Universe. According to modern estimates, 76% of cosmic mass is hydrogen and 23% helium; only 1% remains for all other elements! Thus, the world's matter can be called hydrogen-helium. These two elements dominate stars, planetary nebulae and interstellar gas.
Rice. 1. Element abundance curves on Earth (top) and in space.
The “cosmic” curve reflects the exceptional role of hydrogen and helium in the universe and the special importance of the helium group in the structure of the atomic nucleus. The greatest relative abundance are those elements and those isotopes whose mass number is divided into four: 16 O, 20 Ne, 24 Mg, etc.
Probably, all planets of the solar system contain radiogenic (formed during alpha decay) helium, and large ones also contain relict helium from space. Helium is abundantly present in the atmosphere of Jupiter: according to some data it is 33%, according to others – 17%. This discovery formed the basis of the plot of one of the stories of the famous scientist and science fiction writer A. Azimov. At the center of the story is a plan (possibly feasible in the future) for the delivery of helium from Jupiter, and even the delivery of an armada of cybernetic machines on cryotrons to the nearest satellite of this planet - Jupiter V (more about them below). Immersed in the liquid helium of Jupiter's atmosphere (ultralow temperatures and superconductivity are necessary conditions for the operation of cryotrons), these machines will turn Jupiter V into the brain center of the solar system...
The origin of stellar helium was explained in 1938 by German physicists Bethe and Weizsäcker. Later, their theory received experimental confirmation and refinement with the help of particle accelerators. Its essence is as follows.
Helium nuclei are fused at stellar temperatures from protons in fusion processes that release 175 million kilowatt-hours of energy for every kilogram of helium.
Different reaction cycles can lead to helium synthesis.
In conditions of not very hot stars, such as our Sun, the proton-proton cycle apparently predominates. It consists of three successively changing transformations. First, two protons combine at enormous speeds to form a deuteron - a structure made of a proton and a neutron; in this case, the positron and neutrino are separated. Next, the deuteron and proton combine to form light helium with the emission of a gamma quantum. Finally, two 3 He nuclei react, transforming into an alpha particle and two protons. An alpha particle, having acquired two electrons, will then become a helium atom.
The same final result is given by a faster carbon-nitrogen cycle, the significance of which under solar conditions is not very great, but on stars hotter than the Sun, the role of this cycle increases. It consists of six steps - reactions. Carbon plays here the role of a catalyst for the process of proton fusion. The energy released during these transformations is the same as during the proton-proton cycle - 26.7 MeV per helium atom.
The helium synthesis reaction is the basis for the energetic activity of stars and their glow. Consequently, helium synthesis can be considered the forefather of all reactions in nature, the root cause of life, light, heat and meteorological phenomena on Earth.
Helium is not always the end product of stellar fusions. According to the theory of Professor D.A. Frank-Kamenetsky, with the sequential fusion of helium nuclei, 3 Be, 12 C, 16 O, 20 Ne, 24 Mg are formed, and the capture of protons by these nuclei leads to the formation of other nuclei. The synthesis of nuclei of heavy elements up to transuranic elements requires exceptional ultra-high temperatures, which develop on unstable “novae” and “supernovae” stars.
The famous Soviet chemist A.F. Kapustinsky called hydrogen and helium protoelements - elements of primary matter. Is it not this primacy that conceals the explanation for the special position of hydrogen and helium in the periodic table of elements, in particular the fact that the first period is essentially devoid of the periodicity characteristic of other periods?
The best...
The helium atom (aka molecule) is the strongest of molecular structures. The orbits of its two electrons are exactly the same and pass extremely close to the nucleus. To expose the helium nucleus, it is necessary to expend a record amount of energy - 78.61 MeV. Hence the phenomenal chemical passivity of helium.
Over the past 15 years, chemists have managed to obtain more than 150 chemical compounds of heavy noble gases (compounds of heavy noble gases will be discussed in the articles “Krypton” and “Xenon”). However, the inertness of helium remains, as before, beyond suspicion.
Calculations show that even if a way were found to produce, say, helium fluoride or oxide, then during formation they would absorb so much energy that the resulting molecules would be “exploded” by this energy from the inside.
Helium molecules are non-polar. The forces of intermolecular interaction between them are extremely small - less than in any other substance. Hence - the lowest values of critical values, the lowest boiling point, the lowest heat of evaporation and melting. As for the melting temperature of helium, at normal pressure it does not exist at all. Liquid helium at a temperature no matter how close to absolute zero does not solidify unless, in addition to the temperature, it is subject to a pressure of 25 atmospheres or more. There is no other substance like this in nature.
There is also no other gas so negligibly soluble in liquids, especially polar ones, and so little prone to adsorption as helium. It is the best conductor of electricity among gases and the second best conductor of heat, after hydrogen. Its heat capacity is very high and its viscosity is low.
Helium penetrates amazingly quickly through thin partitions made of some organic polymers, porcelain, quartz and borosilicate glass. It is curious that helium diffuses through soft glass 100 times slower than through borosilicate glass. Helium can also penetrate many metals. Only iron and platinum group metals, even when heated, are completely impenetrable to it.
A new method for extracting pure helium from natural gas is based on the principle of selective permeability.
Scientists are showing exceptional interest in liquid helium. Firstly, it is the coldest liquid in which, moreover, not a single substance dissolves noticeably. Secondly, it is the lightest of liquids with a minimum surface tension.
At a temperature of 2.172°K, an abrupt change in the properties of liquid helium occurs. The resulting species is conventionally called helium II. Helium II boils completely differently from other liquids; it does not boil when boiling, its surface remains completely calm. Helium II conducts heat 300 million times better than regular liquid helium (helium I). The viscosity of helium II is practically zero, it is a thousand times less than the viscosity of liquid hydrogen. Therefore, helium II has superfluidity - the ability to flow without friction through capillaries of arbitrarily small diameter.
Another stable isotope of helium, 3 He, goes into a superfluid state at a temperature that is only hundredths of a degree away from the absolute bullet. Superfluid helium-4 and helium-3 are called quantum liquids: they exhibit quantum mechanical effects even before they solidify. This explains the very detailed study of liquid helium. And now they produce a lot of it - hundreds of thousands of liters a year. But solid helium has hardly been studied: the experimental difficulties of studying this coldest body are great. Undoubtedly, this gap will be filled, since physicists expect a lot of new things from understanding the properties of solid helium: after all, it is also a quantum body.
Inert, but very necessary
At the end of the last century, the English magazine Punch published a cartoon in which helium was depicted as a slyly winking little man - an inhabitant of the Sun. The text under the picture read: “Finally, I was caught on Earth! This went on long enough! I wonder how long it will take until they figure out what to do with me?”
Indeed, 34 years passed from the discovery of terrestrial helium (the first report of this was published in 1881) before it found practical use. A certain role here was played by the original physical, technical, electrical and, to a lesser extent, chemical properties of helium, which required a long study. The main obstacles were the absent-mindedness and high cost of element No. 2.
The Germans were the first to use helium. In 1915, they began filling their airships that bombed London with it. Soon, lightweight but non-flammable helium became an indispensable filler for aeronautical vehicles. The decline in airship construction that began in the mid-30s led to some decline in helium production, but only for a short time. This gas increasingly attracted the attention of chemists, metallurgists and mechanical engineers.
Many technological processes and operations cannot be carried out in air. To avoid interaction of the resulting substance (or feedstock) with air gases, special protective environments are created; and there is no more suitable gas for these purposes than helium.
Inert, lightweight, mobile, and a good conductor of heat, helium is an ideal means for pressing highly flammable liquids and powders from one container to another; It is these functions that it performs in missiles and guided missiles. Individual stages of producing nuclear fuel take place in a helium protective environment. Fuel elements of nuclear reactors are stored and transported in containers filled with helium.
With the help of special leak detectors, the action of which is based on the exceptional diffusion ability of helium, they identify the slightest possibility of leakage in nuclear reactors and other systems under pressure or vacuum.
Recent years have been marked by a renewed rise in airship construction, now on a higher scientific and technical basis. In a number of countries, airships with helium filling with a carrying capacity of 100 to 3000 tons have been built and are being built. They are economical, reliable and convenient for transporting large-sized cargo, such as gas pipelines, oil refineries, power line supports, etc. The 85% helium and 15% hydrogen filling is fireproof and only reduces lift by 7% compared to a hydrogen filling.
High-temperature nuclear reactors of a new type, in which helium serves as the coolant, have begun to operate.
Liquid helium is widely used in scientific research and technology. Ultra-low temperatures favor in-depth knowledge of matter and its structure - at higher temperatures, subtle details of energy spectra are masked by the thermal movement of atoms.
There already exist superconducting solenoids made from special alloys that create strong magnetic fields at liquid helium temperatures (up to 300 thousand oersteds) with negligible energy consumption.
At the temperature of liquid helium, many metals and alloys become superconductors. Superconducting relays - cryotrons - are increasingly used in the designs of electronic computers. They are simple, reliable, and very compact. Superconductors, and with them liquid helium, are becoming necessary for electronics. They are included in the designs of infrared radiation detectors, molecular amplifiers (masers), optical quantum generators (lasers), and instruments for measuring ultrahigh frequencies.
Of course, these examples do not exhaust the role of helium in modern technology. But if it were not for the limited nature of natural resources and the extreme dissipation of helium, it would have found many more applications. It is known, for example, that when canned in helium, food products retain their original taste and aroma. But “helium” canned food still remains a “thing in itself”, because there is not enough helium and it is used only in the most important industries and where it cannot be done without it. Therefore, it is especially offensive to realize that with flammable natural gas, much larger quantities of helium pass through chemical synthesis apparatuses, furnaces and furnaces and escape into the atmosphere than those extracted from helium-bearing sources.
Now it is considered profitable to release helium only in cases where its content in natural gas is not less than 0.05%. The reserves of such gas are constantly decreasing, and it is possible that they will be exhausted before the end of this century. However, the problem of “helium deficiency” will probably be solved by this time - partly through the creation of new, more advanced methods for separating gases, extracting from them the most valuable, albeit insignificant fractions, and partly thanks to controlled thermonuclear fusion. Helium will become an important, albeit by-product, of the activity of “artificial suns”.
Helium isotopes
There are two stable isotopes of helium in nature: helium-3 and helium-4. The light isotope is distributed on Earth a million times less than the heavy one. This is the rarest stable isotope existing on our planet. Three more isotopes of helium have been obtained artificially. They are all radioactive. The half-life of helium-5 is 2.4·10 –21 seconds, helium-6 is 0.83 seconds, helium-8 is 0.18 seconds. The heaviest isotope, interesting because in its nuclei there are three neutrons per proton, was first studied in Dubna in the 60s. Attempts to obtain helium-10 have so far been unsuccessful.
Last solid gas
Helium was the last of all gases to be converted into liquid and solid states. The particular difficulties of liquefying and solidifying helium are explained by the structure of its atom and some features of its physical properties. In particular, helium, like hydrogen, at temperatures above – 250°C, when expanding, does not cool, but heats up. On the other hand, the critical temperature of helium is extremely low. That is why liquid helium was first obtained only in 1908, and solid helium in 1926.
Helium air
Air in which all or most of the nitrogen is replaced by helium is no longer news today. It is widely used on land, underground and under water.
Helium air is three times lighter and much more mobile than ordinary air. It behaves more actively in the lungs - it quickly supplies oxygen and quickly evacuates carbon dioxide. That is why helium air is given to patients with breathing disorders and some operations. It relieves suffocation, treats bronchial asthma and diseases of the larynx.
Breathing helium air practically eliminates nitrogen embolism (caisson disease), to which divers and specialists of other professions who work under conditions of high pressure are susceptible during the transition from high pressure to normal. The cause of this disease is quite significant, especially with high blood pressure, the solubility of nitrogen in the blood. As the pressure decreases, it is released in the form of gas bubbles, which can clog blood vessels, damage nerve nodes... Unlike nitrogen, helium is practically insoluble in body fluids, so it cannot cause decompression sickness. In addition, helium air eliminates the occurrence of “nitrogen narcosis,” which is externally similar to alcohol intoxication.
Sooner or later, humanity will have to learn to live and work on the seabed for a long time in order to seriously take advantage of the mineral and food resources of the shelf. And at great depths, as the experiments of Soviet, French and American researchers have shown, helium air is still indispensable. Biologists have proven that prolonged breathing of helium air does not cause negative changes in the human body and does not threaten changes in the genetic apparatus: the helium atmosphere does not affect the development of cells and the frequency of mutations. There are works whose authors consider helium air to be the optimal air medium for spacecraft making long flights into the Universe. But so far, artificial helium air has not yet risen beyond the Earth’s atmosphere.
As many people know, the most common and lightest element on earth is hydrogen, while helium in our world takes second place! Helium, the second element of Mendeleev's periodic table, is an inert monatomic gas that has no color, taste, or smell. It has the lowest boiling point of all substances (-269 o C). Has 8 isotopes. Each of them is unique in its properties.
History of discovery
The discoverer of helium can rightfully be considered the French astronomer, director of the observatory in Meudon, Pierre Jules César Jansen. In 1868, while studying the sun, namely the chromosphere, an astronomer captured a line of bright yellow color, which was initially and erroneously attributed to the spectrum of sodium. But, a few years later, in 1871, Pierre, together with the English astronomer Joseph Lockyer, established that the line found by Jansen did not belong to any of the chemical elements known at that time. Helium got its name from the word “helios”, which translated from Greek means sun! First of all, scientists assumed that the found element was a metal, but these days, we can say with confidence that this was a false assumption.
As many people know, absolutely all gases can be brought into a liquid state, but this, of course, will require certain conditions. Liquefied was discovered only in 1908. Dutch physicist Heike Kamerlingh Onnes lowered the pressure of gas flowing through an inductor, after first cooling the helium.
Solid helium was obtained only 20 years later in 1926. A student of Kamerlingh Onnes, he was able to obtain gas crystals by increasing the helium pressure above 35 atmospheres and cooling the gas to an extremely low temperature.
Let's start with the fact that helium cannot enter into chemical reactions at all, and also has no oxidation states. Helium is a monatomic gas and has only one electron level (shell), being an extremely stable gas, since it has a first level completely filled with electrons, which indicates a strong influence of the nucleus on electrons. Helium atoms not only do not react with other substances, moreover, they do not even combine with each other.
Liquid helium has a number of absolutely unique properties. In the 30s of the 20th century, at even lower temperatures, an extremely strange and incredible phenomenon was noticed - when helium is cooled to a temperature just 2 degrees above absolute zero, its unexpected transformation occurs. The surface of the liquid becomes absolutely calm and smooth, not a single bubble, not the slightest bubbling of the liquid. Liquid helium turns into a superfluid liquid. Such helium can climb up the walls and “escape” from the vessel in which it is stored; this occurs due to the zero viscosity of the liquefied gas. It can become a fountain with zero friction, which means that such a fountain can flow indefinitely. Despite all the theories, scientists have found that liquefied helium is not an easy liquid. For example, starting with 2He, it turned out that liquefied gas consists of two interpenetrating liquids: a normal (viscous) and a superfluid (zero viscosity) component. The superfluid component is ideal and has zero friction when flowing in any vessels and capillaries.
As for solid helium, at the moment, scientists are conducting numerous experiments and experiments. Solid 4He has a quantum effect such as a crystallization wave. This effect is based on the oscillation of the phase boundary in the “crystal-liquid” system. It is enough to pump such helium a little, and the phase boundary between a liquid and a solid will be similar to the boundary of two liquids!
Use of helium in industry
Basically, helium is needed to obtain extremely low temperatures, as well as in metallurgy for the smelting of pure metals. Also, 2He is not only one of the best coolants, but also a good propellant (E939) in the food industry.
With the help of helium, it is possible to determine the location of faults in the thickness of the Earth, since it is released during the decay of radioactive elements with which the earth's crust is saturated. The helium concentration at the exit of the crack is 50 -100 times higher than normal.
Moreover, aircraft such as airships are filled with helium. Helium is much lighter than air, so the lifting force of such ships is very high. Yes, hydrogen is lighter than helium. So why not use it? Hydrogen is a flammable element, and fueling airships with it is extremely dangerous.
Danger
Any excess of gas concentration can be hazardous to human health. Inhaling air with high concentrations of helium can cause loss of consciousness, severe vomiting and even death. Death occurs as a result of oxygen starvation due to the fact that it does not enter the lungs