Helium is a simple or complex substance. Discovery of helium

On August 18, 1868, the French scientist Pierre Jansen, during a total solar eclipse in the Indian city of Guntur, first explored the chromosphere of the Sun. Spectroscopy of solar prominences, along with the hydrogen lines - blue, blue-green and red - revealed a very bright yellow line, initially taken by Jansen and other astronomers who observed it to be the sodium D line. Independently, English astronomer Norman Lockyer discovered an unknown yellow line in the spectrum with a wavelength of 587.56 nm, and designated it D3. Two years later, Lockyer, together with the English chemist Edward Frankland, came to the conclusion that this bright yellow line did not belong to any of the previously known chemical elements and proposed giving the new element the name “helium” (from the Greek. hlioz- "Sun").

Being in nature, receiving:

Helium is second in abundance in the Universe after hydrogen - about 23% by mass. However, helium is rare on Earth, resulting from the alpha decay of heavy elements. Within the eighth group, helium ranks second in content in the earth's crust (after argon). Helium reserves in the atmosphere, lithosphere and hydrosphere are estimated at 5·10 14 m 3. Helium-bearing natural gases usually contain up to 2% helium by volume (rarely 8-16%). The average helium content in terrestrial matter is 3 g/t. The highest concentration of helium is observed in minerals containing uranium, thorium and samarium: kleveite, fergusonite, samarskite, gadolinite, monazite (monazite sands in India and Brazil), thorianite. The helium content in these minerals is 0.8-3.5 l/kg, and in thorianite it reaches 10.5 l/kg. Natural helium consists of two stable isotopes: 4 He and 3 He. Six more artificial radioactive isotopes of helium are known.
In industry, helium is obtained from helium-containing natural gases.

Physical properties:

The simple substance helium is non-toxic, colorless, odorless and tasteless. Under normal conditions it is a monatomic gas, Tbp = 4.2 K (the lowest among all simple substances). At atmospheric pressure, it does not transform into the solid phase even at temperatures extremely close to absolute zero.
Under normal conditions, helium behaves almost like an ideal gas. Density 0.17847 kg/m3. It has a thermal conductivity (0.1437 W/(m K) at zero) greater than that of other gases except hydrogen. Helium's refractive index is closer to unity than that of any other gas. Helium is less soluble in water than any other known gas (at 20°C about 8.8 ml/l). Its diffusion rate through solid materials is three times higher than that of air and approximately 65% ​​higher than that of hydrogen.
When current is passed through a helium-filled tube, discharges of various colors are observed, depending mainly on the gas pressure in the tube.

Chemical properties:

Helium is the least chemically active element of the eighth group of the periodic table. In the gas phase, it can form (under the action of an electric discharge or ultraviolet radiation) so-called excimer molecules, in which the excited electronic states are stable and the ground state is unstable: diatomic He 2 molecules, HeF fluoride, HeCl chloride. The lifetime of such particles is very short, usually a few nanoseconds. Unlike many other gases, helium does not form clathrates, since small helium atoms “escape” from voids in the structure of water that are too large for them.

Application:

The unique properties of helium are widely used:
- in metallurgy as a protective inert gas for smelting pure metals;
- registered in the food industry as a food additive E939, as a propellant and packaging gas;
- as a refrigerant for obtaining ultra-low temperatures;
- for filling aeronautical vessels (airships), balloons and weather balloon shells;
- as a coolant in some types of nuclear reactors;
- as a carrier in gas chromatography;
- to search for leaks in pipelines and boilers;
- for filling gas discharge tubes;
- as a component of the working fluid in helium-neon lasers;
- in neutron scattering technology as a polarizer and filler for position-sensitive neutron detectors;
- in breathing mixtures for deep-sea diving;
- to change the timbre of the vocal cords (the effect of increased voice pitch) due to the difference in the density of the usual air mixture and helium, etc.;
- 3 He nuclide is a promising fuel for thermonuclear energy.

The chemical element helium was first discovered on the Sun and only then on Earth.

A key role in the history of the discovery of helium was played by Norman Lockyer, the founder of one of the world's leading scientific publications - the journal Nature. In preparation for the publication of the magazine, he became acquainted with the London scientific establishment and became interested in astronomy. This was a time when, inspired by the Kirchhoff-Bunsen discovery, astronomers were just beginning to study the spectrum of light emitted by stars. Lockyer himself managed to make a number of important discoveries - in particular, he was the first to show that sunspots are colder than the rest of the solar surface, and he was also the first to point out that the Sun has an outer shell, calling it chromosphere. In 1868, while studying the light emitted by atoms in prominences—huge ejections of plasma from the surface of the Sun—Lockyer noticed a number of previously unknown spectral lines ( cm. Spectroscopy). Attempts to obtain the same lines in the laboratory failed, from which Lockyer concluded that he had discovered a new chemical element. Lockyer called it helium, from the Greek helios- "Sun".

Scientists were perplexed as to how to react to the appearance of helium. Some suggested that an error had been made in interpreting the spectra of the prominences, but this point of view received fewer and fewer supporters as more and more astronomers were able to observe the Lockyer lines. Others argued that the Sun contains elements that do not exist on Earth - which, as already mentioned, contradicts the main point about the laws of nature. Still others (there was a minority) believed that someday helium would be found on Earth.

In the late 1890s, Lord Rayleigh and Sir William Ramsay conducted a series of experiments that led to the discovery of argon. Ramsay modified his setup to use it to study the gases released by uranium-containing minerals. Ramsay discovered unknown lines in the spectrum of these gases and sent samples to several colleagues for analysis. Upon receiving the sample, Lockyer immediately recognized the lines that he had observed in sunlight more than a quarter of a century earlier. The helium mystery has been solved: the gas is undoubtedly found on the Sun, but it also exists here on Earth. Nowadays, this gas is best known in everyday life as a gas for inflating airships and balloons ( cm. Graham's Law), and in science - thanks to its application in cryogenics, technologies for achieving ultra-low temperatures.

Coronium and nebulium

The question of whether there are chemical elements somewhere in the Universe that are not found on Earth has not lost its relevance in the 20th century. When studying the outer solar atmosphere - solar crowns, consisting of hot, highly rarefied plasma, astronomers discovered spectral lines that they could not identify with any of the known terrestrial elements. Scientists have suggested that these lines belong to a new element, which is called coronium. And when studying the spectra of some nebulae- distant accumulations of gases and dust in the Galaxy - another mysterious lines were discovered. They were attributed to another “new” element - nebulia. In the 1930s, the American astrophysicist Ira Sprague Bowen (1898-1973) came to the conclusion that the nebulium lines actually belong to oxygen, but acquired this appearance due to extreme conditions existing on the Sun and in nebulae, and these conditions cannot be reproduced in earthly laboratories. Coronium turned out to be highly ionized iron. And these lines got the name prohibited lines.

Joseph Norman LOCKYER
Joseph Norman Lockyer, 1836-1920

English scientist. Born in the town of Rugby in the family of a military doctor. Lockyer came to science in an unusual way, starting his career as an official in the War Ministry. To earn extra money, he took advantage of public interest in science and began publishing a popular science magazine. The first issue of the magazine was published in 1869 Nature, and for 50 years Lockyer remained its editor. He participated in many expeditions observing total solar eclipses. One of these expeditions led him to the discovery of helium. Lockyer is also known as the founder of archaeoastronomy - the science that studies the astronomical meaning of ancient structures such as Stonehenge - and the author of many popular science books.

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 uranium- and thorium-rich minerals have fairly 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.

Helium(He) is an inert gas, which is the second element of the periodic table of elements, as well as the second element in lightness and abundance in the Universe. It belongs to simple substances and under standard conditions (Standard temperature and pressure) is a monatomic gas.

Helium It is tasteless, colorless, odorless and contains no toxins.

Among all simple substances, helium has the lowest boiling point (T = 4.216 K). At atmospheric pressure, it is impossible to obtain solid helium, even at temperatures close to absolute zero - to transform into a solid form, helium requires a pressure above 25 atmospheres. There are few chemical compounds of helium and all of them are unstable under standard conditions.
Naturally occurring helium consists of two stable isotopes, He and 4He. The “He” isotope is very rare (isotopic abundance 0.00014%) with 99.99986% for the 4He isotope. In addition to natural ones, 6 artificial radioactive isotopes of helium are also known.
The appearance of almost everything in the Universe, helium, was the primary nucleosynthesis that occurred in the first minutes after the Big Bang.
Currently, almost all helium is formed from hydrogen as a result of thermonuclear fusion occurring in the interior of stars. On our planet, helium is formed during the alpha decay of heavy elements. That part of helium that manages to leak through the Earth’s crust comes out as part of natural gas and can account for up to 7% of its composition. To highlight helium from natural gas, fractional distillation is used - a process of low-temperature separation of elements.

History of the discovery of helium

On August 18, 1868, a total solar eclipse was expected. Astronomers around the world were actively preparing for this day. They hoped to solve the mystery of prominences - luminous protrusions visible at the moment of a total solar eclipse along the edges of the solar disk. Some astronomers believed that the prominences were high lunar mountains, which at the moment of a total solar eclipse were illuminated by the rays of the Sun; others thought that the prominences were mountains on the Sun itself; still others saw fiery clouds of the solar atmosphere in the solar protrusions. The majority believed that prominences were nothing more than an optical illusion.

In 1851, during a solar eclipse observed in Europe, the German astronomer Schmidt not only saw solar protrusions, but also managed to see that their outlines were changing over time. Based on his observations, Schmidt concluded that prominences are hot gas clouds ejected into the solar atmosphere by giant eruptions. However, even after Schmidt’s observations, many astronomers still considered the fiery projections to be an optical illusion.

Only after the total eclipse of July 18, 1860, which was observed in Spain, when many astronomers saw the solar protrusions with their own eyes, and the Italian Secchi and the Frenchman Dellar managed not only to sketch, but also photograph them, no one had any doubts about the existence of prominences .

By 1860, a spectroscope had already been invented - a device that makes it possible, by observing the visible part of the optical spectrum, to determine the qualitative composition of the body from which the observed spectrum is obtained. However, on the day of the solar eclipse, none of the astronomers used a spectroscope to examine the spectrum of the prominences. They remembered the spectroscope when the eclipse was already over.

That is why, in preparation for the solar eclipse of 1868, every astronomer included a spectroscope in the list of observation instruments. Jules Jansen, a famous French scientist, did not forget this device when he went to India to observe prominences, where the conditions for observing a solar eclipse, according to astronomers’ calculations, were the best.

At the moment when the sparkling disk of the Sun was completely covered by the Moon, Jules Jansen, using a spectroscope, examining the orange-red flames escaping from the surface of the Sun, saw in the spectrum, in addition to the three familiar lines of hydrogen: red, green-blue and blue, a new one, unfamiliar – bright yellow. None of the substances known to chemists of that time had such a line in the part of the spectrum where Jules Jansen discovered it. The same discovery, but at home in England, was made by astronomer Norman Lockyer.

On October 25, 1868, the Paris Academy of Sciences received two letters. One, written the day after the solar eclipse, came from Guntur, a small town on the east coast of India, from Jules Jansen; another letter, dated October 20, 1868, was from England from Norman Lockyer.

The letters received were read out at a meeting of professors at the Paris Academy of Sciences. In them, Jules Jansen and Norman Lockyer, independently of each other, reported the discovery of the same “solar matter.” Lockyer proposed to call this new substance, found on the surface of the Sun using a spectroscope, helium from the Greek word for sun - helios.

This coincidence surprised the scientific meeting of professors of the Academies and at the same time testified to the objective nature of the discovery of a new chemical substance. In honor of the discovery of the substance of solar torches (prominences), a medal was struck. On one side of this medal there are portraits of Jansen and Lockyer, and on the other there is an image of the ancient Greek sun god Apollo in a chariot drawn by four horses. Under the chariot there was an inscription in French: “Analysis of solar protrusions on August 18, 1868.”

In 1895, the London chemist Henry Myers drew the attention of William Ramsay, a famous English physical chemist, to the then forgotten article of the geologist Hildebrand. In this article, Hildebrand argued that some rare minerals, when heated in sulfuric acid, emit a gas that does not burn and does not support combustion. Among these rare minerals was kleveite, found in Norway by Nordenskiöld, the famous Swedish explorer of the polar regions.

Ramsay decided to investigate the nature of the gas contained in kleveite. In all the chemical stores in London, Ramsay's assistants managed to buy only... one gram of kleveite, paying only 3.5 shillings for it. Having isolated several cubic centimeters of gas from the resulting amount of kleveite and purified it from impurities, Ramsay examined it using a spectroscope. The result was unexpected: the gas released from kleveite turned out to be... helium!

Not trusting his discovery, Ramsay turned to William Crookes, the largest specialist in spectral analysis in London at that time, with a request to study the gas isolated from kleveite.

Crookes examined the gas. The result of the study confirmed Ramsay's discovery. So on March 23, 1895, a substance was discovered on Earth that had been found on the Sun 27 years earlier. On the same day, Ramsay published his discovery, sending one message to the Royal Society of London and another to the famous French chemist Academician Berthelot. In a letter to Berthelot, Ramsay asked to report his discovery to a scientific meeting of professors at the Paris Academy.

15 days after Ramsay, independently of him, the Swedish chemist Langlais isolated helium from kleveite and, like Ramsay, reported his discovery of helium to the chemist Berthelot.

For the third time, helium was discovered in the air, where, according to Ramsay, it should have come from rare minerals (cleveite, etc.) during destruction and chemical transformations on Earth.

Helium was also found in small quantities in the water of some mineral springs. For example, it was found by Ramsay in the healing spring of Cauterets in the Pyrenees Mountains, the English physicist John William Rayleigh found it in the waters of springs at the famous resort of Bath, the German physicist Kaiser discovered helium in the springs flowing in the Black Forest mountains. However, helium was found most abundantly in some minerals. It is found in samarskite, fergusonite, columbite, monazite, and uranite. The mineral thorianite from the island of Ceylon contains particularly high amounts of helium. A kilogram of thorianite releases 10 liters of helium when heated red-hot.

It was soon discovered that helium is found only in those minerals that contain radioactive uranium and thorium. Alpha rays emitted by some radioactive elements are nothing more than the nuclei of helium atoms.

From the history...

Its unusual properties make it possible to widely use helium for a variety of purposes. The first, absolutely logical, based on its lightness, is use in balloons and airships. Moreover, unlike hydrogen, it is not explosive. This property of helium was used by the Germans in the First World War on combat airships. The downside of using it is that an airship filled with helium will not fly as high as a hydrogen one.

During the First World War, the German command used airships (zeppelins) to bomb large cities, mainly the capitals of England and France. Hydrogen was used to fill them. Therefore, the fight against them was relatively simple: an incendiary projectile that hit the shell of the airship ignited hydrogen, which instantly flared up and the device burned out. Of the 123 airships built in Germany during the First World War, 40 were burned by incendiary shells. But one day the general staff of the British army was surprised by a message of particular importance. Direct hits from incendiary shells on the German Zeppelin were unsuccessful. The airship did not burst into flames, but slowly flowed out with some unknown gas and flew back.

Military experts were perplexed and, despite an urgent and detailed discussion of the issue of the Zeppelin’s non-flammability from incendiary shells, they could not find the necessary explanation. The riddle was solved by the English chemist Richard Threlfall. In a letter to the British Admiralty, he wrote: "... I believe that the Germans have invented some way of producing helium in large quantities, and this time they filled the shell of their zeppelin not with hydrogen, as usual, but with helium..."

The credibility of Threlfall's arguments, however, was diminished by the fact that there were no significant sources of helium in Germany. True, helium is contained in the air, but there is little of it there: one cubic meter of air contains only 5 cubic centimeters of helium. The Linde system refrigeration machine, which turns several hundred cubic meters of air into liquid in one hour, could produce no more than 3 liters of helium during this time.

3 liters of helium per hour! And to fill a zeppelin you need 5-6 thousand cubic meters. m. To obtain such an amount of helium, one Linde machine had to work without stopping for about two hundred years; two hundred such machines would give the required amount of helium in one year. The construction of 200 plants for converting air into liquid to produce helium is economically very unprofitable and practically pointless.

Where did German chemists get helium from?

This issue, as it turned out later, was resolved relatively simply. Long before the war, German shipping companies carrying goods to India and Brazil were instructed to load returning ships not with ordinary ballast, but with monazite sand, which contains helium. Thus, a reserve of “helium raw materials” was created - about 5 thousand tons of monazite sand, from which helium for the zeppelins was obtained. In addition, helium was extracted from the water of the Nauheim mineral spring, which gave up to 70 cubic meters. m of helium daily.

The incident with the fireproof zeppelin was the impetus for new searches for helium. Chemists, physicists, and geologists began to intensively search for helium. It suddenly acquired enormous value. In 1916, 1 cubic meter of helium cost 200,000 rubles in gold, i.e. 200 rubles per liter. If we consider that a liter of helium weighs 0.18 g, then 1 g of it cost over 1000 rubles.

Helium became the object of hunting for merchants, speculators, and stockbrokers. Helium was discovered in significant quantities in natural gases emerging from the bowels of the earth in America, in the state of Kansas, where, after America entered the war, a helium plant was built near the city of Fort Worth. But the war ended, helium reserves remained unused, the cost of helium fell sharply and at the end of 1918 amounted to about four rubles per cubic meter.

The helium obtained with such difficulty was used by the Americans only in 1923 to fill the now peaceful airship Shenandoah. It was the world's first and only helium-filled air cargo-passenger ship. However, his “life” turned out to be short-lived. Two years after its birth, the Shenandoah was destroyed by a storm. 55 thousand cubic meters m, almost the entire world supply of helium, collected over six years, dissipated without a trace in the atmosphere during a storm that lasted only 30 minutes.

Application of helium

Helium in nature

Mostly 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 - He 4, 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.

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 uranium- and thorium-rich minerals have fairly 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.

There is little helium on Earth: 1 m 3 of air contains only 5.24 cm 3 of helium, and every kilogram of earthly material contains 0.003 mg of helium. But in terms of prevalence in the Universe, helium ranks second after hydrogen: helium accounts for about 23% of cosmic mass. Approximately half of all helium is concentrated in the earth's crust, mainly in its granite shell, which has accumulated the main reserves of radioactive elements. The helium content in the earth's crust is low - 3 x 10 -7% by mass. Helium accumulates in free gas accumulations in the subsoil and in oils; Such deposits reach industrial scales. Maximum concentrations of helium (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 helium in the composition of natural gases.

Helium extraction

Helium is 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). Значительные его концентрации известны в некоторых месторождениях природного газа Канады, США (шт. Канзас, Техас, Нью-Мексико, Юта).

World helium reserves amount to 45.6 billion cubic meters. Large deposits are located in the United States (45% of world resources), followed by Russia (32%), Algeria (7%), Canada (7%) and China (4%).
The United States also leads in helium production (140 million cubic meters per year), followed by Algeria (16 million).

Russia ranks third in the world - 6 million cubic meters per year. The Orenburg Helium Plant is currently the only domestic source of helium production, and gas production is declining. In this regard, gas fields in Eastern Siberia and the Far East with high concentrations of helium (up to 0.6%) are of particular importance. One of the most promising is Kovykta ha is a condensate field located in the north of the Irkutsk region. According to experts, it contains about 25% of the world's x helium reserves.

Indicator name	Helium (grade A) (according to TU 51-940-80)	Helium (grade B) (according to TU 51-940-80)	High purity helium, grade 5.5 (according to TU 0271-001-45905715-02)	High purity helium, grade 6.0 (according to TU 0271-001-45905715-02)
Helium, no less
Nitrogen, no more
Oxygen + argon
Neon, nothing more
Water vapor, no more
Hydrocarbons, no more
CO2 + CO, no more
Hydrogen, no more

Safety

– Helium is not toxic, not flammable, not explosive
– Helium is allowed to be used in any crowded places: at concerts, advertising events, stadiums, shops.
– Helium gas is physiologically inert and does not pose a danger to humans.
– Helium is not dangerous for the environment, so neutralization, recycling and disposal of its residues in cylinders is not required.
– Helium is much lighter than air and dissipates in the upper layers of the Earth’s atmosphere.

Helium (grades A and B according to TU 51-940-80)
Technical name	Helium gas
Chemical formula
OON number
Transport hazard class
Physical properties
Physical state	Under normal conditions - gas
Density, kg/m³	Under normal conditions (101.3 kPa, 20 C), 1627
Boiling point, C at 101.3 kPa
Temperature of the 3rd point and its equilibrium pressure C, (mPa)
Solubility in water	insignificant
Fire and explosion hazard	fire and explosion proof
Stability and reactivity
Stability	Stable
Reactivity	Inert gas
Danger to humans
Toxic effects	Non-toxic
Environmental hazard	Has no harmful effect on the environment
Facilities	Any means apply

Helium storage and transportation

Helium gas can be transported by all modes of transport in accordance with the rules for transporting goods on a specific mode of transport. Transportation is carried out in special brown steel cylinders and containers for helium transportation. Liquid helium is transported in transport vessels such as STG-40, STG-10 and STG-25 with a volume of 40, 10 and 25 liters.

Rules for the transportation of cylinders with technical gases

The transportation of dangerous goods in the Russian Federation is regulated by the following documents:

1. “Rules for the transportation of dangerous goods by road” (as amended by Orders of the Ministry of Transport of the Russian Federation dated June 11, 1999 No. 37, dated October 14, 1999 No. 77; registered with the Ministry of Justice of the Russian Federation on December 18, 1995, registration No. 997).

2. “European Agreement on the International Carriage of Dangerous Goods by Road” (ADR), to which Russia officially joined on April 28, 1994 (RF Government Decree No. 76 dated 02/03/1994).

3. “Road Rules” (Traffic Regulations 2006), namely Article 23.5, which establishes that “Transportation... of dangerous goods... is carried out in accordance with special rules.”

4. “Code of the Russian Federation on Administrative Offences”, Article 12.21 Part 2 of which provides for liability for violation of the rules for transporting dangerous goods in the form of “an administrative fine for drivers in the amount of one to three times the minimum wage or deprivation of the right to drive vehicles for a period of one to three months; for officials responsible for transportation - from ten to twenty times the minimum wage."

In accordance with clause 3, clause 1.2, “The Rules do not apply to... transportation of a limited amount of dangerous substances on one vehicle, the transportation of which can be considered as the transportation of non-dangerous cargo.” It also explains that “A limited amount of dangerous goods is determined in the requirements for the safe transportation of a specific type of dangerous goods. When determining it, it is possible to use the requirements of the European Agreement on the International Carriage of Dangerous Goods (ADR).” Thus, the question of the maximum quantity of substances that can be transported as non-dangerous goods comes down to the study of section 1.1.3 of ADR, which establishes exceptions from the European rules for the transport of dangerous goods associated with various circumstances.

So, for example, in accordance with paragraph 1.1.3.1 “The provisions of ADR do not apply... to the transport of dangerous goods by private persons, when these goods are packaged for retail sale and are intended for their personal consumption, household use, leisure or sports, provided that measures have been taken to prevent any leakage of the contents under normal conditions of carriage."

However, a group of exemptions formally recognized by the rules for the transportation of dangerous goods are exemptions associated with quantities transported in one transport unit (clause 1.1.3.6).

All gases are classified into the second class of substances according to the ADR classification. Non-flammable, non-toxic gases (groups A - neutral and O - oxidizing) belong to the third transport category, with a maximum quantity limited to 1000 units. Highly flammable (group F) - to the second, with a maximum quantity limited to 333 units. By “unit” here we mean 1 liter of the capacity of the vessel containing the compressed gas, or 1 kg of liquefied or dissolved gas. Therefore, the maximum quantity of gases that can be carried in one transport unit as non-dangerous cargo is as follows:

Exists three main sources of receipt helium:

• from helium-containing natural gases
• from minerals
• out of thin air

Producing helium from natural gas

The main method of producing helium is the method of fractional condensation from natural helium-containing gases, i.e. deep cooling method. Moreover, its characteristic property is used - the lowest boiling point compared to known substances. This makes it possible to condense all the gases accompanying helium, primarily methane and nitrogen. The process is usually carried out in two stages:

• release of so-called raw helium (concentrate containing 70-90% He)
• purification to obtain technically pure helium.

The figure below shows one of the installation diagrams for extracting helium from natural gas.

The gas is compressed to 25 atmospheres and enters the installation under this pressure. Cleaning from (CO 2) and partial drying of gas is carried out in scrubbers, which are irrigated with a solution containing 10-20% monoethanolamine, 70-80% diethylene glycol and 5-10% water. After scrubbers, 0.003-0.008% carbon dioxide CO 2 remains in the gas, and the dew point does not exceed 5°C. Further drying is carried out in adsorbers with silica gel, where a dew point temperature of -45°C is reached.

Under a pressure of about 20 atmospheres, clean dry gas enters the preliminary heat exchanger 1, where it is cooled to -28°C by reverse gas flows. In this case, condensation of heavy hydrocarbons occurs, which are separated in separator 2. In the ammonia refrigerator 3, the gas is cooled to -45°C, the condensate is separated in separator 4. In the main heat exchanger 5, the gas temperature is reduced to -110°C, as a result of which a significant part of the gas is condensed methane The vapor-liquid mixture (about 20% of the liquid) is throttled to a pressure of 12 atmospheres in the first counter-flow condenser 6, at the outlet of which the vapor-gas mixture is enriched with helium up to 3%. The condensate formed in the tubes flows into the stripping section, on the plates of which the helium dissolved in it is removed from the liquid, which joins the steam-gas flow.

The liquid is throttled to 1.5 atmospheres into the annulus of the condenser, where it serves as a refrigerant. The steam formed here is removed through heat exchangers 5 and 1. The steam-gas mixture leaving condenser 6 and containing up to 3% He, under a pressure of 12 atmospheres, goes to the second counter-flow condenser 7, consisting of two parts: in the lower part there is a coil heat exchanger, in in the tubes of which the bottom liquid, throttled from 12 to 1.5 atmospheres, evaporates, and in the upper part there is a straight-tube heat exchanger, in the inter-tube space of which nitrogen boils at a temperature of -203 ° C and a pressure of 0.4 atmospheres. As a result of condensation of the components of the gas mixture in the lower part of the apparatus 7, the gas is enriched with helium up to 30-50%, and in the upper part - up to 90-92%.

Crude helium of this composition under a pressure of 11-12 atmospheres enters heat exchangers, where it is heated and removed from the installation. Since natural gas contains small hydrogen impurities, the hydrogen concentration in raw helium increases to 4-5%. Hydrogen is removed by catalytic hydrogenation followed by gas drying in adsorbers with silica gel. Raw helium is compressed to 150-200 atmospheres by a membrane compressor 8, cooled in a heat exchanger 9 and supplied to a direct-flow coil condenser 10, cooled by nitrogen boiling under vacuum. Condensate (liquid) is collected in separator 11 and periodically removed, and non-condensed gas containing approximately 98% He goes to adsorber 12 with activated carbon, cooled with liquid nitrogen. The helium leaving the adsorber contains impurities of less than 0.05% and enters the cylinders 13 as a product.

Natural gases in the USA are especially rich in helium, which determines the widespread use of helium in this country.

Obtaining helium from minerals

Another source of helium is some radioactive minerals containing uranium, thorium and samarium:

• slander
• fergusonite
• samarskite
• gadolinite
• monazite
• thorianite

In particular monazite sands, a large deposit of which is in Travancore (India): monazites of this deposit contain about 1 cm 3 of helium per 1 g of ore.

To obtain helium from a monocyte, it is necessary to heat the monocyte in a closed vessel to 1000°C. Helium is released along with carbon dioxide (CO 2), which is then absorbed by a solution of sodium hydroxide (NaOH). The residual gas contains 96.6% He. Further purification is carried out at 600°C on magnesium metal to remove nitrogen, and then at 580°C on calcium metal to remove remaining impurities. The production gas contains over 99.5% He. From 1000 tons of monazite sand you can get about 80 m 3 of pure helium. Such the method for producing helium is not of technical or industrial interest..

Getting helium from air

Helium is found in small amounts in the air, from which it can be obtained as a by-product in the production of oxygen and nitrogen from air, described in the article "". In industrial distillation columns to separate air above liquid nitrogen, the remaining gaseous mixture of neon and helium is collected. The picture below shows Claude's apparatus, specially adapted for separating such a mixture.

The gas leaving the apparatus through valve D is cooled in the coil S, which is poured with liquid nitrogen from T to condense the residual nitrogen. If valve R is opened slightly, a mixture containing very little nitrogen is obtained. With this method of industrial production of helium, in addition to the difficulty of the need to process a large amount of air, there is also an additional difficulty - the need separation of helium from neon. This separation can be accomplished using liquid hydrogen in which the neon is solidified, or by adsorption of neon onto activated carbon cooled with liquid nitrogen.

Obtaining helium from air is impractical due to its small amount - 0.00046% volume or 0.00007% weight. Calculations show that the cost of one cubic meter of helium extracted from air will be thousands of times higher than when extracting it from natural gases. Such a high cost, of course, excludes the possibility of industrial separation of helium from the air.

For example: To extract 1 cubic meter of helium, you need to release 116 tons of nitrogen.