The role of helium in the life of the earth. Resident (Resident) play for money or for free without registration online - slot machine Resident
Helium is an inert gas of the 18th group of the periodic table. It is the second lightest element after hydrogen. Helium is a colorless, odorless and tasteless gas that becomes liquid at -268.9 °C. Its boiling and freezing points are lower than those of any other known substance. It is the only element that does not solidify when cooled at normal atmospheric pressure. It takes 25 atmospheres for helium to solidify at 1 K.
Discovery history
Helium was discovered in the gaseous atmosphere surrounding the Sun by the French astronomer Pierre Jansen, who in 1868 during an eclipse discovered a bright yellow line in the spectrum of the solar chromosphere. This line was originally thought to represent the element sodium. In the same year, the English astronomer Joseph Norman Lockyer observed a yellow line in the solar spectrum that did not correspond to the known D 1 and D 2 lines of sodium, and so he named it the D 3 line. Lockyer concluded that it was caused by a substance in the Sun unknown on Earth. He and the chemist Edward Frankland used the Greek name for the sun, helios, to name the element.
In 1895, British chemist Sir William Ramsay proved the existence of helium on Earth. He received a sample of the uranium-bearing mineral cleveite, and after examining the gases formed when it was heated, he found that the bright yellow line in the spectrum coincided with the D 3 line observed in the spectrum of the Sun. Thus, the new element was finally installed. In 1903, Ramsay and Frederic Soddu determined that helium is a spontaneous decay product of radioactive substances.
Distribution in nature
Helium makes up about 23% of the entire mass of the universe, and the element is the second most abundant in space. It is concentrated in stars, where it is formed from hydrogen as a result of thermonuclear fusion. Although helium is found in the earth's atmosphere at a concentration of 1 part per 200,000 (5 ppm) and is found in small amounts in radioactive minerals, meteoric iron, and mineral springs, large amounts of the element are found in the United States (especially in Texas, New York). Mexico, Kansas, Oklahoma, Arizona and Utah) as a component (up to 7.6%) of natural gas. Small reserves have been found in Australia, Algeria, Poland, Qatar and Russia. In the earth's crust, the concentration of helium is only about 8 parts per billion.
isotopes
The nucleus of each helium atom contains two protons, but like other elements, it has isotopes. They contain one to six neutrons, so their mass numbers range from three to eight. The stable ones are the elements in which the mass of helium is determined by the atomic numbers 3 (3 He) and 4 (4 He). All the rest are radioactive and decay very quickly into other substances. Terrestrial helium is not the original component of the planet, it was formed as a result of radioactive decay. Alpha particles emitted by the nuclei of heavy radioactive substances are nuclei of the 4 He isotope. Helium does not accumulate in large quantities in the atmosphere because the Earth's gravity is not strong enough to prevent it from gradually escaping into space. Traces of 3 He on Earth are explained by the negative beta decay of the rare element hydrogen-3 (tritium). 4 He is the most common of the stable isotopes: the ratio of the number of atoms 4 He to 3 He is about 700 thousand to 1 in the atmosphere and about 7 million to 1 in some helium-containing minerals.
Physical properties of helium
The boiling and melting points of this element are the lowest. For this reason, helium exists except under extreme conditions. Gaseous He dissolves less in water than any other gas, and the rate of diffusion through solids is three times that of air. Its refractive index comes closest to 1.
The thermal conductivity of helium is second only to that of hydrogen, and its specific heat capacity is unusually high. At ordinary temperatures, it heats up during expansion, and cools down below 40 K. Therefore, at T<40 K гелий можно превратить в жидкость путем расширения.
An element is a dielectric unless it is in an ionized state. Like other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge when the voltage remains below the ionization potential.
Helium-4 is unique in that it has two liquid forms. The regular one is called helium I and exists at temperatures ranging from a boiling point of 4.21 K (-268.9 °C) to about 2.18 K (-271 °C). Below 2.18 K, the thermal conductivity of 4 He becomes 1000 times greater than that of copper. This form is called helium II to distinguish it from the normal form. It is superfluid: the viscosity is so low that it cannot be measured. Helium II spreads into a thin film on the surface of whatever it touches, and this film flows without friction even against gravity.
Less abundant helium-3 forms three distinct liquid phases, two of which are superfluid. Superfluidity in 4 He was discovered by a Soviet physicist in the mid-1930s, and the same phenomenon in 3 He was first noticed by Douglas D. Osherov, David M. Lee, and Robert S. Richardson from the USA in 1972.
A liquid mixture of two isotopes of helium-3 and -4 at temperatures below 0.8 K (-272.4 °C) is divided into two layers - almost pure 3 He and a mixture of 4 He with 6% helium-3. The dissolution of 3 He into 4 He is accompanied by a cooling effect, which is used in the design of cryostats, in which the helium temperature drops below 0.01 K (-273.14 °C) and is maintained at this temperature for several days.
Connections
Under normal conditions, helium is chemically inert. In extreme conditions, you can create element connections that are not stable at normal temperatures and pressures. For example, helium can form compounds with iodine, tungsten, fluorine, phosphorus, and sulfur when subjected to an electrical glow discharge when bombarded with electrons or in the plasma state. Thus, HeNe, HgHe 10 , WHe 2 and molecular ions He 2 + , He 2 ++ , HeH + and HeD + were created. This technique also made it possible to obtain neutral He 2 and HgHe molecules.
Plasma
In the Universe, ionized helium is predominantly distributed, the properties of which differ significantly from molecular helium. Its electrons and protons are not bound, and it has a very high electrical conductivity even in a partially ionized state. Charged particles are strongly affected by magnetic and electric fields. For example, in the solar wind, helium ions, along with ionized hydrogen, interact with the Earth's magnetosphere, causing the aurora borealis.
Discovery of deposits in the USA
After drilling a well in 1903 in Dexter, Kansas, non-flammable gas was obtained. Initially, it was not known that it contained helium. What gas was found was determined by state geologist Erasmus Haworth, who collected samples of it and at the University of Kansas, with the help of chemists Cady Hamilton and David McFarland, found that it contains 72% nitrogen, 15% methane, 1% hydrogen and 12% was not identified. After further analysis, the scientists found that 1.84% of the sample was helium. So they learned that this chemical element is present in huge quantities in the bowels of the Great Plains, from where it can be extracted from natural gas.
industrial production
This made the United States the world leader in helium production. At the suggestion of Sir Richard Threlfall, the US Navy funded three small experimental plants to produce this substance during World War I to provide barrage balloons with a light, non-flammable lifting gas. A total of 5,700 m 3 of 92% He was produced under this program, although only less than 100 liters of gas had previously been produced. Part of this volume was used in the world's first helium airship C-7, which made its first flight from Hampton Roads to Bolling Field on December 7, 1921.
Although the low-temperature gas liquefaction process was not advanced enough at the time to be significant during World War I, production continued. Helium was mainly used as a lift gas in aircraft. Demand for it grew during World War II, when it was used in shielded arc welding. The element was also important in the Manhattan atomic bomb project.
US National Reserve
In 1925, the United States government established the National Helium Reserve at Amarillo, Texas for the purpose of providing military airships in times of war and commercial airships in times of peace. Use of the gas declined after World War II, but the supply was increased in the 1950s to provide, among other things, its supply as a coolant used in the production of oxyhydrogen rocket fuel during the space race and the Cold War. U.S. helium use in 1965 was eight times the peak wartime consumption.
Since the Helium Act of 1960, the Bureau of Mines has contracted 5 private companies to extract the element from natural gas. For this program, a 425-kilometer gas pipeline was built connecting these plants to a partially depleted government gas field near Amarillo, Texas. The helium-nitrogen mixture was pumped into an underground storage and remained there until it was needed.
By 1995, a billion cubic meters of stock had been built and the National Reserve was $1.4 billion in debt, prompting the US Congress to phase it out in 1996. Following the adoption of the helium privatization law in 1996, the Ministry of Natural Resources began to liquidate the storage facility in 2005.
Purity and production volumes
Helium produced before 1945 was about 98% pure, with the remaining 2% being nitrogen, which was sufficient for airships. In 1945, a small amount of 99.9% gas was produced for use in arc welding. By 1949, the purity of the resulting element reached 99.995%.
For many years, the United States produced over 90% of the world's commercial helium. Since 2004, 140 million m 3 of it has been produced annually, 85% of which is produced in the USA, 10% was produced in Algeria, and the rest - in Russia and Poland. The main sources of helium in the world are the gas fields of Texas, Oklahoma and Kansas.
Receipt process
Helium (purity 98.2%) is isolated from natural gas by liquefying other components at low temperatures and high pressures. The adsorption of other gases with chilled activated carbon achieves a purity of 99.995%. A small amount of helium is produced by liquefying air on a large scale. About 3.17 cubic meters can be obtained from 900 tons of air. m of gas.
Applications
Noble gas has found application in various fields.
- Helium, whose properties make it possible to obtain ultra-low temperatures, is used as a cooling agent in the Large Hadron Collider, superconducting magnets in MRI machines and nuclear magnetic resonance spectrometers, satellite equipment, as well as for liquefying oxygen and hydrogen in Apollo rockets.
- As an inert gas for welding aluminum and other metals, in the production of optical fibers and semiconductors.
- To create pressure in the fuel tanks of rocket engines, especially those that operate on liquid hydrogen, since only gaseous helium retains its state of aggregation when hydrogen remains liquid);
- He-Ne are used to scan barcodes at checkouts in supermarkets.
- A helium-ion microscope produces better images than an electron microscope.
- Due to its high permeability, noble gas is used to check for leaks, for example, in car air conditioning systems, as well as to quickly inflate airbags in a collision.
- Low density allows you to fill decorative balloons with helium. Inert gas has replaced explosive hydrogen in airships and balloons. For example, in meteorology, helium balloons are used to lift measuring instruments.
- In cryogenic technology, it serves as a coolant, since the temperature of this chemical element in the liquid state is the lowest possible.
- Helium, whose properties provide it with low reactivity and solubility in water (and blood), mixed with oxygen, has found application in breathing compositions for scuba diving and caisson work.
- Meteorites and rocks are analyzed for this element to determine their age.
Helium: element properties
The main physical properties of He are as follows:
- Atomic number: 2.
- Relative mass of a helium atom: 4.0026.
- Melting point: no.
- Boiling point: -268.9 °C.
- Density (1 atm, 0 °C): 0.1785 g/p.
- Oxidation states: 0.
HELIUM, He (lat. Helium, from the Greek. helios - the Sun, since it was first discovered in the solar spectrum * a. helium; n. Helium; f. helium; and. helio), - an element of group VIII of the periodic system of Mendeleev , refers to inert gases, atomic number 2, atomic mass 4.0026. Natural helium consists of two stable isotopes 3 He and 4 He. It was discovered in 1868 by the French astronomer J. Jansen and the English astronomer J. N. Lockyer during a spectroscopic study of solar prominences. Helium was first isolated in 1895 by the English physicist W. Ramsay from the radioactive mineral cleveite.
helium properties
Under normal conditions, helium is a colorless and odorless gas. 0.178 kg / m 3, boiling t - 268.93 ° C. Helium is the only element that does not solidify in a liquid state at normal pressure, no matter how deeply it is cooled. In 1938, the Soviet physicist P. L. Kapitsa discovered superfluidity in 4 He—the ability to flow without viscosity. The lowest pressure required to transfer liquid helium to solid is 2.5 MPa, while melting t is 272.1 ° C. (at 0°С) 2.1.10 -2 W/m.K. The helium molecule consists of one atom, its radius is from 0.085 (net) to 0.133 nm (van der Waals) (0.85-1.33 E), About 8.8 ml of helium dissolves in 1 liter of water at 20 ° C Stable chemical compounds of helium have not been obtained.
Helium in nature
In terms of prevalence in the Universe, helium takes 2nd place after. There is little helium on Earth: 1 m 3 of air contains 5.24 cm 3 of helium, the average content is 3.10 -7%. There are 3 genetic components of helium in the stratal lithosphere - radiogenic, primordial and atmospheric helium. Radiogenic helium is formed everywhere during radioactive transformations of heavy elements and various nuclear reactions, primeval helium enters the lithosphere both from deep rocks that have occluded primeval helium and preserved it since the formation of the planet, and from space along with cosmic dust, meteorites, etc. Atmospheric helium enters precipitation from the air, during the processes of sedimentogenesis, as well as with infiltrating surface waters.
The value of the ratio 3 He/ 4 He in radiogenic helium is n. 1.4.10 -6. The 4 He isotope absolutely dominates in terrestrial helium. The main amount of 4 He was formed during the a-decay of natural radioactive elements (radioisotopes, actinouranium and). Insignificant sources of 4 He and 3 He formation in the lithosphere are nuclear reactions (neutron fission of lithium, etc.), tritium decay, etc. Radiogenic 4 He 3 He/ 4 He = (2±1 ).10 -8 . The tectonically disturbed earth's crust (rift zones, deep faults, eruptive apparatuses, with tectonomagmatic or seismic activity, etc.) is characterized by an increased amount of 3 He 3 He/ 4 He = n.10 -5 . For other geological structures, the ratio 3 He/ 4 He in reservoir gases and fluids varies within 10 -8 -10 -7 . The difference in the 3He/4He isotope-helium ratios in mantle and crustal helium is an indicator of the present relationship between deep fluids and the mantle. Due to the lightness, inertness and high permeability of helium, most of the rock-forming ones do not retain it, and helium migrates through the fracture-pore spaces of rocks, dissolving in the fluids filling them, sometimes far away from the main formation zones.
Helium is an obligatory impurity in all gases that form independent accumulations in the earth's crust or go outside in the form of natural gas jets. Usually helium is an insignificant admixture with other gases; in rare cases, its amount reaches several% (by volume); the maximum concentrations of helium were found in underground gas accumulations (8-10%), uranium gases (10-13%) and water-dissolved gases (18-20%).
Getting helium
In industry, helium is obtained from helium-containing gases by deep cooling (down to -190°C), a small amount - during the operation of air separation plants. In this case, the main gas components are condensed (frozen out), and the remaining helium concentrate is purified from hydrogen and. Diffuse methods for extracting helium are also being developed.
Transportation and storage of helium - in highly sealed containers. Helium of the 1st and 2nd grades is usually transported in steel cylinders of various capacities, usually up to 40 liters, under pressure up to 15 MPa. Helium storages are also arranged in underground salt chambers, and raw helium (about 60% He and 40% N 2) is stored in depleted underground gas structures. Over long distances, helium is supplied in compressed and liquid form using specially equipped vehicles, as well as by gas pipelines (for example, in the USA).
Helium use
The use of helium is based on its unique properties such as complete inertness (welding in a helium atmosphere, production of ultrapure and semiconductor materials, additive in breathing mixtures, etc.), high permeability (leak detectors in high and low pressure apparatuses). helium is the only chemical element that makes it possible to obtain ultra-low temperatures necessary for all types of superconducting systems and installations (cryoenergy). Liquid helium is a refrigerant in scientific research.
Helium, usually produced by the radioactive decay of uranium-238 and uranium-235, was found in the Sun's atmosphere 13 years earlier than on Earth. This gas has the lowest critical values, the lowest boiling point, the lowest heat of evaporation and melting. As for the melting point of helium, at normal pressure it does not exist at all. There is no other substance like it in nature...
Helium is an unusual element, and its history is somewhat mysterious and incomprehensible. It was found in the Sun's 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 terrestrial minerals containing radioactive elements.
How is helium formed?
Mostly terrestrial helium is formed during the radioactive decay of uranium-238, uranium-235, thorium and unstable products of their decay. Helium in the earth's crust accumulates slowly. One ton of granite, containing 2 g of uranium and 10 g of thorium, produces only 0.09 mg of helium in a million years - half a cubic centimeter. In very few minerals rich in uranium and thorium, the helium content is quite high - a few cubic centimeters of helium per gram.
Most minerals undergo weathering, recrystallization, etc. processes over time, and helium leaves them. Helium bubbles released from crystalline structures partially dissolve in groundwater. Another part of the 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, hundreds of millions of years. Layers of loose rocks act as traps here, the voids of which are filled with gas. The bed for such gas reservoirs is usually water or oil, and from above they are blocked by gas-tight strata of dense rocks.
Helium synthesis - the beginning of life
The bowels and atmosphere of our planet are poor in helium. But this does not mean that it is not enough everywhere in the Universe. According to modern estimates, 76% of the cosmic mass is hydrogen and 23% helium; on all other elements, only one percent remains. Thus, the world matter can be called hydrogen-helium. These two elements predominate in stars, planetary nebulae, and interstellar gas. The helium fusion reaction is the basis of the energy activity of stars, 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.
Natural gases are practically the only source of raw materials for the industrial production of helium. Helium is present in natural gases as a minor impurity. Its content does not exceed thousandths, hundredths, rarely - tenths of a percent. Large (1.5–10%) helium content of methane-nitrogen deposits is an extremely rare phenomenon. For separation from other gases, the exceptional volatility of helium associated with its low fluidization temperature is used. After all other components of natural gas are condensed by deep cooling, helium gas is pumped out. Then it is purified from impurities. The purity of the factory helium reaches 99.995%. Liquid helium is obtained by liquefying gaseous helium.
helium properties
gaseous helium- an inert gas without color, smell and taste. liquid helium- a colorless, odorless liquid with a boiling point at normal atmospheric pressure of 101.3 kPa (760 mm Hg) 4.215 K (minus 268.9 ° C) and a density of 124.9 kg / m 3.
Helium is non-toxic, non-flammable, non-explosive, but at high concentrations in the air it causes a state of oxygen deficiency and suffocation. Liquid helium is a low-boiling liquid that can cause frostbite on the skin and damage to the mucous membranes of the eyes.
helium atom(aka molecule) - the strongest of molecular structures. The orbits of its two electrons are exactly the same and pass extremely close to the nucleus. To expose a helium nucleus, you need to spend a record high energy (78.61 eV). From this follows the phenomenal chemical passivity of helium.
Helium molecules are non-polar. The forces of intermolecular interaction between them are extremely small - less than in any other substance. For this reason, helium has the lowest critical values, the lowest boiling point, and the lowest heat of evaporation and melting. As for the melting point of helium, at normal pressure it does not exist at all. Liquid helium at a temperature arbitrarily close to absolute zero does not solidify if, in addition to temperature, it is not affected by a pressure of 25 or more atmospheres. There is no other such substance in nature. It is the best conductor of electricity among gases and the second, after hydrogen, conductor of heat. Its heat capacity is very high, and its viscosity, on the contrary, is small.
Helium, airships, divers and nuclear power...
Helium was first used in Germany. In 1915, the Germans began to fill their airships bombing London with it. Soon, light but non-flammable helium became an indispensable filler for aeronautic vehicles. The decline of the airship industry, which began in the mid-1930s, led to a slight decline in helium production, but only for a short time. This gas increasingly attracted the attention of chemists, metallurgists and machine builders.
Another area of application of helium is due to the fact that many technological processes and operations cannot be carried out in an air environment. To avoid the 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.
in helium protective environment undergo separate stages of obtaining nuclear fuel. Fuel elements of nuclear reactors are stored and transported in containers filled with helium. With the help of special leak detectors, whose action is based on the exceptional diffusion ability of helium, they detect the slightest possibility of a leak in nuclear reactors and other systems under pressure or vacuum.
In scientific research and technology widely applied liquid helium. Ultra-low temperatures favor in-depth knowledge of matter and its structure - at higher temperatures, the subtle details of the energy spectra are masked by the thermal motion of atoms.
There are already superconducting solenoids made of special alloys that create strong magnetic fields (up to 300 thousand oersteds) at the temperature of liquid helium with negligible energy costs. At the temperature of liquid helium, many metals and alloys become superconductors. Superconducting cryotron relays are increasingly being used in the design of electronic computers. They are simple, reliable, very compact. Superconductors, and with them liquid helium, become essential for electronics. They are included in the design of infrared radiation detectors, molecular amplifiers (masers), optical quantum generators (lasers), and devices for measuring microwave frequencies.
Helio-oxygen mixtures became a reliable means of preventing decompression sickness and gave a big gain in time when lifting divers. As is known, the solubility of gases in liquids, other things being equal, is directly proportional to pressure. Divers working under high pressure have much more nitrogen dissolved in their blood compared to normal conditions that exist on the surface of the water. When rising from a depth, when the pressure approaches normal, the solubility of nitrogen decreases, and its excess begins to be released. If the ascent is made quickly, the release of excess dissolved gases occurs so violently that the blood and water-rich tissues of the body, saturated with gas, foam with a mass of nitrogen bubbles - like champagne when a bottle is opened.
The formation of nitrogen bubbles in the blood vessels disrupts the functioning of the heart, their appearance in the brain disrupts its functions, and all this together leads to severe disorders in the body's vital functions and, as a result, to death. In order to prevent the development of the described phenomena, known under the name of "caisson disease", the rise of divers, that is, the transition from high pressure to normal, is carried out very slowly.
In this case, the excess of dissolved gases is released gradually and no painful disorders occur. With the use of artificial air, in which nitrogen is replaced by less soluble helium, the possibility of harmful disorders is almost completely eliminated. This allows divers to increase the depth of descent (up to 100 meters or more) and lengthen the time spent under water.
"Helium" air has a density three times less than the density of ordinary air. Therefore, it is easier to breathe such air than usual (the work of the respiratory muscles decreases). This circumstance is important in case of respiratory diseases. That's why helium air also applies in medicine in the treatment of asthma, suffocation and other diseases.
Not yet eternal, but already harmless
At the Los Alamos National Laboratory named after E. Fermi (New Mexico) developed new engine, which can seriously change the perception of the car as one of the main sources of pollution. With an efficiency comparable to an internal combustion engine (30–40%), it is devoid of its main disadvantages: moving parts that need lubrication to reduce friction and wear, and environmentally harmful emissions of products of incomplete combustion of fuel.
In fact, we are talking about an improvement of the well-known external combustion engine, proposed by the Scottish priest R. Stirling back in 1816. This engine was not widely used in vehicles due to its more complex design compared to the internal combustion engine, greater material consumption and cost. But the thermoacoustic energy converter proposed by American scientists, in which compressed helium serves as the working medium, compares favorably with its predecessor by the absence of bulky heat exchangers that prevented its use in passenger cars, and in the near future can become an environmentally acceptable alternative not only to the internal combustion engine, but also solar energy converter, refrigerator, air conditioner. The scale of its application is still hard to imagine.
Helium(lat. Helium), symbol He, a 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 Helium consists of 2 stable isotopes: 3 He and 4 He (the content of 4 He sharply prevails).
History reference. Helium was first 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 composition of solar prominences spectroscopically. The images they received contained a bright yellow line (the so-called D3 line) that could not be attributed to any of the elements known at the time. In 1871, Lockyer explained its origin by the presence of a new element on the Sun, which they called helium (from the Greek helios - Sun). On Earth, Helium was first isolated in 1895 by the Englishman W. Ramsay from the radioactive mineral cleveite. The same line appeared in the spectrum of the gas released during heating of kleveite.
Distribution of helium in nature. There is little Helium on Earth: 1 m 3 of air contains only 5.24 cm 3 of Helium, and each kilogram of terrestrial material contains 0.003 mg of Helium. In terms of prevalence in the Universe, Helium ranks second after hydrogen: Helium accounts for about 23% of the cosmic mass.
On Earth, Helium (more precisely, the 4 He isotope) is constantly formed during the decay of uranium, thorium and other radioactive elements (in total, the earth's crust contains about 29 radioactive isotopes producing 4 He).
Approximately half of all helium is concentrated in the earth's crust, mainly in its granite shell, which accumulated the main reserves of radioactive elements. The content of helium in the earth's crust is small - 3·10 -7% by weight. Helium accumulates in free gas accumulations of the bowels and in oil; such deposits reach an industrial scale. The maximum concentrations of Helium (10-13%) were found in free gas accumulations and gases from uranium mines and (20-25%) in gases released spontaneously from groundwater. The older the age of gas-bearing sedimentary rocks and the higher the content of radioactive elements in them, the more Helium is in the composition of natural gases. Volcanic gases are usually characterized by a low content of Helium.
Helium production on an industrial scale is carried out from natural and petroleum gases of both hydrocarbon and nitrogen composition. According to 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 Гелий содержится во многих нефтегазовых месторождениях. Значительные его концентрации известны в некоторых месторождениях природного газа Канады, США (штаты Канзас, Техас, Нью-Мексико, Юта).
Isotopes, atom and molecule of Helium. In natural helium of any origin (atmospheric, from natural gases, from radioactive minerals, meteorite, etc.), the isotope 4 He predominates. The content of 3 He is usually low (depending on the source of Helium, it ranges from 1.3·10 -4 to 2·10 -8%) and only in Helium isolated from meteorites does it reach 17-31.5%. The rate of formation of 4 He 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 Helium is formed in 7.9 million years; however, since this process proceeds constantly, during the existence of the Earth, it should have ensured the content of Helium in the atmosphere, lithosphere and hydrosphere, which is much higher than the present one (it is about 5 10 14 m 3). Such a shortage of helium is explained by its constant volatilization from the atmosphere. Light atoms of Helium, falling into the upper layers of the atmosphere, gradually acquire a speed higher than the second cosmic one and thereby get the opportunity to overcome the forces of the earth's gravity. The simultaneous formation and volatilization of helium lead to the fact that its concentration in the atmosphere is practically constant.
The 3 He isotope, in particular, is formed in the atmosphere during the β-decay of the heavy hydrogen isotope - tritium (T), which, in turn, arises during the interaction of cosmic radiation neutrons with atmospheric nitrogen:
14 7 N + 3 0 n → 12 6 C + 3 1 T.
The nuclei of the 4 He atom (consisting of 2 protons and 2 neutrons), called alpha particles or helions, are the most stable among the compound nuclei. The binding energy of nucleons (protons and neutrons) in 4 He has a maximum value compared to the nuclei of other elements (28.2937 MeV); therefore, the formation of 4 He nuclei from hydrogen nuclei (protons) 1 H is accompanied by the release of a huge amount of energy. It is believed that this nuclear reaction:
4 1 H = 4 He + 2β + + 2n
[simultaneously with 4 He, two positrons (β +) and two neutrinos (ν) 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 Helium accumulate in the Universe.
Physical properties of Helium. Under normal conditions, helium is a monatomic gas, colorless and odorless. Density 0.17846 g/l, t bale -268.93°С, t pl -272.2°С. Thermal conductivity (at 0°C) 143.8 10 -3 W / (cm K) . The radius of the Helium atom, determined by various methods, ranges from 0.85 to 1.33 Å. About 8.8 ml of Helium dissolves in 1 liter of water at 20°C. The primary ionization energy of Helium is greater than that of any other element - 39.38 10 -13 J (24.58 eV); Helium has no electron affinity. Liquid Helium, consisting only of 4 He, exhibits a number of unique properties.
Chemical properties of Helium. So far, attempts to obtain stable chemical compounds of helium have ended in failure.
Getting Helium. In industry, helium is obtained from helium-containing natural gases (at present, deposits containing > 0.1% Helium are mainly exploited). Helium is separated from other gases by deep cooling, using the fact that it is more difficult to liquefy than all other gases.
Helium application. Due to its inertness, helium is widely used to create a protective atmosphere in the melting, cutting, and welding of active metals. Helium is less electrically conductive than another inert gas - argon, and therefore an electric arc in an atmosphere of Helium gives higher temperatures, which significantly increases the speed of arc welding. Due to its low density, combined with incombustibility, helium is used to fill stratostats. Helium's high thermal conductivity, its chemical inertness, and its extremely low ability to enter into a nuclear reaction with neutrons make it possible to use Helium to cool nuclear reactors. Liquid Helium is the coldest liquid on Earth and serves as a refrigerant in various scientific studies. One of the methods for determining their absolute age is based on the determination of the helium content in radioactive minerals. Due to the fact that helium is very poorly soluble in blood, it is used as an integral part of the artificial air supplied for breathing by divers (replacing nitrogen with helium prevents the occurrence of bends). The possibilities of using helium in the atmosphere of a spacecraft cabin are also being studied.
Helium liquid. The relatively weak interaction of Helium atoms causes it to remain gaseous to lower temperatures than any other gas. The maximum temperature below which it can be liquefied (its critical temperature T k) is 5.20 K. Liquid Helium is the only non-freezing liquid: at normal pressure, Helium remains liquid at arbitrarily low temperatures and solidifies only at pressures exceeding 2 5 MN/m 2 (25 at).
Helium is a truly noble gas. It has not yet been possible to force him to enter into any reactions. 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 noticeably dissolves in liquid helium.
Solid helium cannot be obtained at any temperature unless pressure is increased.
In the history of the discovery, research and application of this element, there are names of many prominent physicists and chemists from different countries. They were interested in helium, worked with helium: Jansen (France), Lockyer, Ramsay, Crookes, Rutherford (England), Palmieri (Italy), Keesom, Camerling-Onnes (Holland), Feynman, Onsager (USA), Kapitsa, Kikoin, Landau ( Soviet Union) and many other prominent scientists.
The uniqueness of the appearance of the helium atom is determined by the combination of two amazing natural structures in it - absolute champions in terms of compactness and strength. In the helium nucleus, helium-4, both intranuclear shells are saturated - both proton and neutron. The electronic doublet framing this nucleus is also saturated. These designs hold the key to understanding the properties of helium. Hence its phenomenal chemical inertness and the record-breaking small size of its atom.
The role of the nucleus of the helium atom - alpha particles in the history of the formation and development of nuclear physics is enormous. If you remember, it was the study of the scattering of alpha particles that led Rutherford to the discovery of the atomic nucleus. When nitrogen was bombarded with alpha particles, the interconversion of elements was carried out for the first time - something that many generations of alchemists have dreamed of 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 #2 is a very unusual element.
terrestrial helium
Helium is an unusual element, and its history is unusual. It was discovered in the atmosphere of the Sun 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 terrestrial minerals containing radioactive elements.
Helium on the Sun was discovered by the Frenchman J. Jansen, who made his observations in India on August 19, 1868, and the Englishman J.H. Lockyer - October 20 of the same year. The letters of 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, struck by such a strange coincidence, decided to knock out a gold medal in honor of this event.
In 1881, the discovery of helium in volcanic gases was reported by the Italian scientist Palmieri. However, his message, later confirmed, was taken seriously by few scientists. Secondary terrestrial helium was discovered by Ramsay in 1895.
There are 29 isotopes in the earth's crust, during the radioactive decay of which alpha particles are formed - 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 the early geological periods, there probably also existed 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 neptunian series.
By the amount of helium trapped 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 the uranium-238 turns into helium and lead in 4.52 billion years.
Helium in the earth's crust accumulates slowly. One ton of granite, containing 2 g of uranium and 10 g of thorium, produces only 0.09 mg of helium in a million years - half a cubic centimeter. The very few minerals rich in uranium and thorium contain quite a large amount of helium - a few cubic centimeters of helium per gram. However, the share of these minerals in natural helium production is close to zero, as they are very rare.
Natural compounds containing alpha active isotopes are only the primary source, but not the raw material for the industrial production of helium. True, some minerals with a dense structure - native metals, magnetite, garnet, apatite, zircon and others - firmly hold the helium contained in them. However, most minerals eventually undergo processes of weathering, recrystallization, etc., and helium leaves them.
The helium bubbles released from the crystalline structures set off on a journey through the earth's crust. A very small part of them dissolves in groundwater. The formation of more or less concentrated helium solutions requires special conditions, primarily high pressures. Another part of the nomadic helium enters the atmosphere through the pores and cracks of minerals. The remaining gas molecules fall into underground traps, where they accumulate for tens, hundreds of millions of years. 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 from above they are blocked by gas-tight strata of dense rocks.
Since other gases also wander in the earth's crust (mainly methane, nitrogen, carbon dioxide), and, moreover, in much larger quantities, there are no purely helium accumulations. Helium is present in natural gases as a minor impurity. Its content does not exceed thousandths, hundredths, 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. For separation from other gases, the exceptional volatility of helium associated with its low liquefaction temperature is used. After all other components of natural gas are condensed by deep cooling, helium gas is pumped out. Then it is purified from impurities. The purity of the factory helium reaches 99.995%.
Helium reserves on Earth are estimated at 5·10 14 m 3 ; judging by the calculations, it was formed in the earth's crust over 2 billion years ten times more. This discrepancy between theory and practice is understandable. Helium is a light gas and, like hydrogen (albeit more slowly), does not escape from the atmosphere into outer space. Probably, during the existence of the Earth, the helium of our planet was repeatedly updated - the old one escaped into space, and instead of it, fresh - “exhaled” by the Earth entered the atmosphere.
There is at least 200,000 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 the atmosphere is small. Helium is a rare and diffuse gas. For 1 kg of terrestrial material, there is only 0.003 mg of helium, and its content in the air is 0.00052 volume percent. Such a low concentration does not yet allow economical extraction of helium from the air.
Helium in the Universe
The bowels and atmosphere of our planet are poor in helium. But this does not mean that it is not enough everywhere in the Universe. According to modern estimates, 76% of the cosmic mass is hydrogen and 23% helium; only 1% remains on all other elements! Thus, the world matter can be called hydrogen-helium. These two elements predominate in stars, planetary nebulae, and interstellar gas.
Rice. one. 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 significance of the helium group in the structure of the atomic nucleus. Those elements and their isotopes whose mass number is divided into four have the highest relative abundance: 16 O, 20 Ne, 24 Mg, etc.
Probably, all the planets of the solar system contain radiogenic (formed during alpha decay) helium, and large planets also contain relict helium from space. Helium is abundantly represented in the atmosphere of Jupiter: according to some data, it is 33% there, 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. In the center of the story is a plan (possibly feasible in the future) for the delivery of helium from Jupiter, and even transfer to the nearest satellite of this planet - Jupiter V - an armada of cybernetic machines on cryotrons (about them - below). Immersed in the liquid helium of Jupiter's atmosphere (ultra-low 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 the German physicists Bethe and Weizsacker. Later, their theory received experimental confirmation and refinement with the help of particle accelerators. Its essence is as follows.
Helium nuclei are synthesized at stellar temperatures from protons in a fusion process that releases 175 million kilowatt-hours of energy for every kilogram of helium.
Different cycles of reactions can lead to the fusion of helium.
Under the conditions of not very hot stars, such as our Sun, the proton-proton cycle seems to predominate. It consists of three consecutive transformations. First, two protons combine at great speeds to form a deuteron - a structure of a proton and a neutron; in this case, a positron and a neutrino are separated. Further, the deuteron is combined with a proton 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 gives a faster carbon-nitrogen cycle, the significance of which is not very large under solar conditions, but on stars hotter than the Sun, the role of this cycle is enhanced. 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 in the proton-proton cycle - 26.7 MeV per helium atom.
The helium fusion reaction is the basis of the energy activity of stars, 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 fusion. According to the theory of Professor D.A. Frank-Kamenetsky, in the successive 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. For the synthesis of nuclei of heavy elements up to transuranium, exceptional superhigh temperatures are required, which develop on unstable "new" and "supernova" stars.
The famous Soviet chemist A.F. Kapustinsky called hydrogen and helium protoelements - elements of primary matter. Is it not this primacy that explains the special position of hydrogen and helium in the periodic system of elements, in particular the fact that the first period is essentially devoid of the periodicity characteristic of other periods?
The most of the most...
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 a helium nucleus, you need to spend a record high 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 if a way were found to obtain, say, fluoride or helium 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 quantities, the lowest boiling point, the lowest heats of evaporation and melting. As for the melting point of helium, at normal pressure it does not exist at all. Liquid helium at a temperature arbitrarily close to absolute zero does not solidify if, in addition to temperature, it is subjected to a pressure of 25 or more atmospheres. There is no other such substance 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, after hydrogen, conductor of heat. 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. Curiously, helium diffuses through soft glass 100 times slower than through borosilicate glass. Helium can also penetrate many metals. Only iron and metals of the platinum group, even hot ones, are completely impenetrable to it.
A new method for extracting pure helium from natural gas is based on the principle of selective permeability.
Scientists show exceptional interest in liquid helium. Firstly, it is the coldest liquid in which, moreover, not a single substance noticeably dissolves. Secondly, it is the lightest of liquids with a minimum surface tension.
At a temperature of 2.172°K, there is an abrupt change in the properties of liquid helium. The resulting species is conventionally named helium II. Helium II boils quite differently from other liquids, it does not boil when boiling, its surface remains completely calm. Helium II conducts heat 300 million times better than ordinary 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, passes into the 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: quantum mechanical effects appear in them even before they solidify. This explains the very detailed study of liquid helium. Yes, 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 in studying this very cold body are great. Undoubtedly, this gap will be filled, since physicists expect a lot of new things from the knowledge of 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 cunningly winking little man - an inhabitant of the Sun. The text below the picture read: “Finally, they caught me on Earth! It's been long enough! I wonder how long it will be before they figure out what to do with me?”
Indeed, 34 years have passed since the discovery of terrestrial helium (the first report on this was published in 1881) before it found practical application. 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 absent-mindedness and the high cost of element No. 2.
The Germans were the first to use helium. In 1915, they began to fill their airships bombing London with it. Soon, light but non-flammable helium became an indispensable filler for aeronautic vehicles. The decline of the airship industry, which began in the mid-1930s, led to a slight decline in helium production, but only for a short time. This gas increasingly attracted the attention of chemists, metallurgists and machine builders.
Many technological processes and operations cannot be carried out in the air. To avoid the 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, light, mobile, good conductor of heat, helium is an ideal means for transferring flammable liquids and powders from one container to another; it is precisely these functions that it performs in rockets and guided missiles. In a helium protective environment, separate stages of obtaining nuclear fuel take place. Fuel elements of nuclear reactors are stored and transported in containers filled with helium.
With the help of special leak detectors, whose action is based on the exceptional diffusion ability of helium, they detect the slightest possibility of a leak in nuclear reactors and other systems under pressure or vacuum.
Recent years have been marked by a renewed rise in airship building, 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 bulky cargo, such as gas pipelines, oil refineries, power transmission towers, 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 began to operate, in which helium serves as a coolant.
Liquid helium is widely used in scientific research and engineering. Ultra-low temperatures favor in-depth knowledge of matter and its structure - at higher temperatures, the subtle details of the energy spectra are masked by the thermal motion of atoms.
There are already superconducting solenoids made of special alloys that create strong magnetic fields (up to 300,000 oersteds) at the temperature of liquid helium with negligible energy expenditure.
At the temperature of liquid helium, many metals and alloys become superconductors. Superconducting relays - cryotrons are increasingly used in the design of electronic computers. They are simple, reliable, very compact. Superconductors, and with them liquid helium, become essential for electronics. They are included in the design of infrared radiation detectors, molecular amplifiers (masers), optical quantum generators (lasers), and devices for measuring microwave frequencies.
Of course, these examples do not exhaust the role of helium in modern technology. But if it were not for the limited natural resources, not for the extreme dispersion of helium, he would have found many more applications. It is known, for example, that when preserved in a helium environment, food products retain their original taste and aroma. But “helium” canned food is still a “thing in itself”, because helium is not enough and it is used only in the most important industries and where it is indispensable. Therefore, it is especially insulting to realize that with combustible natural gas, much larger amounts of helium pass through chemical synthesis apparatuses, furnaces and furnaces and go into the atmosphere than those extracted from helium-bearing sources.
Now it is considered advantageous to separate helium only in cases where its content in natural gas is not less than 0.05%. The reserves of such gas are decreasing all the time, and it is possible that they will be exhausted before the end of our century. However, the problem of “helium deficiency” will probably be solved by this time - partly due to the creation of new, more advanced methods for separating gases, extracting the most valuable, albeit insignificant fractions from them, and partly due to controlled thermonuclear fusion. Helium will be an important, albeit by-product, product of "artificial suns."
Isotopes of helium
In nature, there are two stable isotopes of helium: helium-3 and helium-4. The light isotope is a million times less common on Earth than the heavy isotope. It is the rarest of the stable isotopes that exist on our planet. Three more helium isotopes have been artificially obtained. All of them are 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 in that there are three neutrons per proton in its nuclei, was first discovered 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 a liquid and solid state. The special 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, 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 - in 1926.
helium air
Air in which all or most of its nitrogen has been replaced by helium is no longer a novelty today. It is widely used on land, underground and underwater.
Helium air is three times lighter and much more mobile than ordinary air. It behaves more actively in the lungs - quickly brings oxygen and quickly evacuates carbon dioxide. That is why helium air is given to patients with respiratory disorders and some operations. It relieves suffocation, treats bronchial asthma and diseases of the larynx.
Breathing helium air practically eliminates nitrogen embolism (caisson disease), which divers and specialists of other professions, whose work takes place under conditions of high pressure, are susceptible to during the transition from high pressure to normal. The cause of this disease is quite significant, especially at high blood pressure, the solubility of nitrogen in the blood. As the pressure decreases, it is released in the form of gas bubbles that 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 anesthesia", outwardly similar to alcohol intoxication.
Sooner or later, mankind will have to learn how to live and work for a long time on the seabed 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 with 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-term flights to the Universe. But so far, artificial helium air has not yet risen beyond the earth's atmosphere.
