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| | HELIUM Chemical Properties |
| Melting point | -272.2 °C(lit.) | | Boiling point | -268.934 °C(lit.) | | density | 0.1785（0℃） | | vapor density | 0.14 (vs air) | | form | gas | | Odor | at 100.00?%. odorless | | Water Solubility | 8.61mL/1000g H2O (101.32kPa, 0°C) [KIR78]; Henry’s law constants, k×10?4: 9.856 (104°C), 6.739 (149.4°C), 2.524 (250.6°C), 1.796 (275.1°C) [POT78] | | Merck | 13,4645 | | Stability: | Stable; extremely unreactive. | | LogP | 0.280 | | CAS DataBase Reference | 7440-59-7(CAS DataBase Reference) | | EPA Substance Registry System | Helium (7440-59-7) |
| | HELIUM Usage And Synthesis |
| Description | Helium is a colorless, odorless, and tasteless monoatomic gas with
an atomic weight of 4, a density of 1.78 g per 1 at 0°C and 1
atmosphere pressure, and an aqueous solubility of 0.97 mL per
100 mL at 50°C. The Bunsen solubility coefficient (the volume,
in mL, of gas at standard conditions dissolved per mL of liquid).
of helium at 38°C is 0.0086 in water, and 0.015 in olive oil. After
hydrogen, helium is the most abundant element in the universe;
these elements are believed to represent 76 and 23 percent, respectively, of all matter in the universe. The earth’s atmosphere, however, contains only 5 ppm of helium. Mineral gases from wells
contain higher concentrations and serve as the principal source for
industrial production. Helium is chemically very inert; it has a
weak tendency to combine with other elements such as fluorine.
It is usually marketed as compressed gas, with the USP grade
containing not less than 99 percent helium.
The largest biological use of helium is the replacement for nitrogen
in synthetic breathing gas mixtures for divers and others working
under high pressure conditions. The low solubility in body fluids
compared to nitrogen decreases the danger of bends on depressurizing. | | Chemical Properties | colourless gas | | Chemical Properties | Helium is a colorless, odorless, and tasteless
gas. It is nonflammable. | | Physical properties | Helium is a colorless, odorless, and tasteless inert gas that is noncombustible and is the leastsoluble of any gas in water and alcohol. As a gas, it diffuses well in solids. Helium’s freezingpoint is –272.2°C, and its boiling point is –268.93°C. Both temperatures are near absolutezero (–273.13°C, or –459.4°F), where all molecular and thermal motion ceases. Liquid heliumhas the lowest temperature of any known substance. Helium’s density is 0.0001785g/cm3.
Helium is the only element that cannot be converted into a solid by lowering the temperature.At normal pressure it remains a liquid at near absolute zero, but if the pressure isincreased, it then turns into a solid. | | Isotopes | There are eight isotopes of helium. Two of these are stable. They are He-3,which makes up just 0.000137% of natural helium found on Earth, and He-4, whichaccounts for 99.999863% of the natural abundance of helium on Earth. Another isotope,He-5, is an extremely rare radioisotope that decays by emitting beta particles toform lithium-6 and lithium-8. | | Origin of Name | From the Greek word helios, meaning the “sun.” Through the process
of spectrometry, it was discovered on the sun before it was found on Earth in 1868. | | Occurrence | Helium is the 73rd most abundant element on Earth, but it is the second most abundant element in the universe, after hydrogen. Together, helium and hydrogen make up 99.9% of all the elements in the universe, but helium makes up only a small trace of the elements on Earth.
Most likely, helium was the first element to be formed after hydrogen during the Big Bang formation of the universe. The theory is that hydrogen atoms combined under great heat and pressure to form helium atoms. The Earth s current helium originally came from the natural decay of radioactive elements deep in the Earth. Much of it seeps up to the surface and escapes into the atmosphere, or it mixes with natural gas deposits deep in the Earth. Like hydrogen, it is a very light gas that escapes through cracks in the Earth s crust and sooner or later escapes from Earth s gravity into the atmosphere.
Helium can be obtained from the atmosphere by lowering the temperature of air until it liquefies. All the other gases in air will turn to a liquid except helium, because it has the lowest boiling point. Since helium, at this stage of cooling, will be the only vapor left, it can be removed as a pure gas. It is commercially more profitable to produce helium by separating it from a mix of natural underground gases, where its concentration is greater that in the atmosphere. Raw natural gas is a mixture of methane, nitrogen, and helium, with traces of other gases. The nitrogen and helium are separated from the methane, which is used as a fuel. This separation is accomplished by fractional distillation wherein the temperature is reduced and the gases are liquefied. As the temperature is reduced, methane is liquefied first, then nitrogen, leaving helium to be collected and sold commercially. Helium is then purified to 99.995%. Most of the world s supply of helium comes from the United States. | | Characteristics | When a second proton and two neutrons are added to a hydrogen nucleus, a helium atomcan form after it collects two electrons. Helium is the most inert of all the noble group 18gases. It is so inactive that it does not even combine with itself. As a gas, helium remains asa single atom. The nuclei of helium are called alpha particles, each of which has a charge of+2 and an atomic mass of 4.
No stable compound of helium has ever been found. However, it is possible for an atom ofhydrogen to combine with helium (and other light noble elements) under special conditionsto form HeH+, an unstable ion.
Helium is not plentiful on Earth and is only the sixth most abundant gas in the atmosphere.It does not accumulate in the atmosphere because it is lighter than air. Some amountof helium continually escapes into space from the outer atmosphere of the Earth.
Liquid helium exhibits some unusual characteristics when supercooled. First, it is the onlyelement that will not turn into a solid by just using pressure. Heat must be removed as thepressure is increased, but helium will freeze at –272.2°C, which is the lowest temperature scientistshave ever achieved. Second, it is an excellent conductor of heat. As a supercold liquid,it will move toward heat—even flow up the sides and over the top of a container. | | History | valence usually 0. Evidence of the existence of helium was first obtained by Janssen during the solar eclipse of 1868 when he detected a new line in the solar spectrum; Lockyer and Frankland suggested the name helium for the new element; in 1895, Ramsay discovered helium in the uranium mineral cleveite, and it was independently discovered in cleveite by the Swedish chemists Cleve and Langlet about the same time. Rutherford and Royds in 1907 demonstrated that α particles are helium nuclei. Except for hydrogen, helium is the most abundant element found throughout the universe. Helium is extracted from natural gas; all natural gas contains at least trace quantities of helium. It has been detected spectroscopically in great abundance, especially in the hotter stars, and it is an important component in both the proton–proton reaction and the carbon cycle, which account for the energy of the sun and stars. The fusion of hydrogen into helium provides the energy of the hydrogen bomb. The helium content of the atmosphere is about 1 part in 200,000. It is present in various radioactive minerals as a decay product. Much of the world’s supply of helium is obtained from wells in Texas, Colorado, and Kansas. The only other known helium extraction plants, outside the United States, in 1999 were in Poland, Russia, China, Algeria, and India. The cost of helium has fallen from $2500/ft3 in 1915 to about 2.5￠/cu.ft. (.028 cu meters) in 1999. Helium has the lowest melting point of any element and has found wide use in cryogenic research, as its boiling point is close to absolute zero. Its use in the study of superconductivity is vital. Using liquid helium, Kurti and co-workers, and others, have succeeded in obtaining temperatures of a few microkelvins by the adiabatic demagnetization of copper nuclei, starting from about 0.01 K. Liquid helium (He4) exists in two forms: He4I and He4II, with a sharp transition point at 2.174 K (3.83 cm Hg). He4I (above this temperature) is a normal liquid, but He4II (below it) is unlike any other known substance. It expands on cooling; its conductivity for heat is enormous; and neither its heat conduction nor viscosity obeys normal rules. It has other peculiar properties. Helium is the only liquid that cannot be solidified by lowering the temperature. It remains liquid down to absolute zero at ordinary pressures, but it can readily be solidified by increasingthe pressure. Solid 3He and 4He are unusual in that both can readily be changed in volume by more than 30% by application of pressure. The specific heat of helium gas is unusually high. The density of helium vapor at the normal boiling point is also very high, with the vapor expanding greatly when heated to room temperature. Containers filled with helium gas at 5 to 10 K should be treated as though they contained liquid helium due to the large increase in pressure resulting from warming the gas to room temperature. While helium normally has a 0 valence, it seems to have a weak tendency to combine with certain other elements. Means of preparing helium diflouride have been studied, and species such as HeNe and the molecular ions He+ and He++ have been investigated. Helium is widely used as an inert gas shield for arc welding; as a protective gas in growing silicon and germanium crystals, and in titanium and zirconium production; as a cooling medium for nuclear reactors, and as a gas for supersonic wind tunnels. A mixture of helium and oxygen is used as an artificial atmosphere for divers and others working under pressure. Different ratios of He/O2 are used for different depths at which the diver is operating. Helium is extensively used for filling balloons as it is a much safer gas than hydrogen. One of the recent largest uses for helium has been for pressurizing liquid fuel rockets. A Saturn booster such as used on the Apollo lunar missions required about 13 million ft3 of helium for a firing, plus more for checkouts. Liquid helium’s use in magnetic resonance imaging (MRI) continues to increase as the medical profession accepts and develops new uses for the equipment. This equipment is providing accurate diagnoses of problems where exploratory surgery has previously been required to determine problems. Another medical application that is being developed uses MRI to determine by blood analysis whether a patient has any form of cancer. Lifting gas applications are increasing. Various companies in addition to Goodyear, are now using “blimps” for advertising. The Navy and the Air Force are investigating the use of airships to provide early warning systems to detect low-flying cruise missiles. The Drug Enforcement Agency has used radar-equipped blimps to detect drug smugglers along the southern border of the U.S. In addition, NASA is currently using helium-filled balloons to sample the atmosphere in Antarctica to determine what is depleting the ozone layer that protects Earth from harmful U.V. radiation. Research on and development of materials which become superconductive at temperatures well above the boiling point of helium could have a major impact on the demand for helium. Less costly refrigerants having boiling points considerably higher could replace the present need to cool such superconductive materials to the boiling point of helium. Natural helium contains two stable isotopes 3He and 4He. 3He is present in very small quantities. Six other isotopes of helium are now recognized. | | Uses | Helium has many uses.
As an inert gas, it is used as the atmosphere in which to “grow” silicon crystals (computerchips).
As a lifting gas, it is used to inflate weather balloons and lighter-than-air ships (blimps)similar to the ones seen taking TV pictures above football games. Even though helium has lesslifting power than hydrogen, it is used for all lighter-than-air ships because it is noncombustibleand thus safer than hydrogen. In addition to blimps, toy balloons are filled with helium.
In arc welding, it is used as an inert gas shield that releases great heat for very long andheavy welds. Helium prevents oxidation of the metal being welded, thus preventing burningand corrosion of the metal. This is one of the major uses of helium.
Helium is used for low-temperature research (–272.2°C or –434°F). It has become importantas a coolant for superconducting electrical systems that, when cooled, offer little resistance to theelectrons passing through a conductor (wire or magnet). When the electrons are “stripped” fromthe helium atom, a positive He++ ion results. The positive helium ions (nuclei) occur in bothnatural and man-made radioactive emissions and are referred to as alpha particles. Helium ions(alpha particles) are used in high-energy physics to study the nature of matter.
In gas discharge lasers, helium transfers the energy to the laser gas such as carbon dioxideor another inert gas;in mixtures with neon and argon for electronic tubes and “neon” signs..
As an inert gas with heat-transfer capability, helium is used in gas-cooled nuclear powerreactors, which operate at a higher efficiency than liquid-cooled nuclear reactors. Theworld’s largest particle accelerators use liquid helium to cool their superconducting magnets.Astronomers use liquid helium to cool their detecting instruments. If this equipment is keptcool, the “thermal noise” produced at higher temperatures is reduced. | | Uses | Gases, diluent. | | Uses | Helium is used as an inert gas shield in arc
welding, as a lifting gas for lighter-than-air aircraft,
and as a gaseous cooling medium in nuclear
reactors. It is also used to provide a protective
atmosphere for growing germanium and
silicon crystals for transistors, to provide a protective
atmosphere in the production of such
reactive metals as titanium and zirconium, to fill
cold-weather fluorescent lamps, to trace leaks in
refrigeration and other closed systems, and to fill neutron and gas thermometers. Its thermal
conductivity makes it an important gas for lasers
and fiber optic production. It is used extensively
in chromatography due to its inertness and high
thermal conductivity. It is used in cryogenic
research such as for superconductivity. In mixtures
with oxygen, it has medical and diving
applications. Radioactive mixtures of helium
with krypton are available to users licensed by
the Nuclear Regulatory Commission. NASA
uses helium for purging and pressurizing the
liquid hydrogen tanks of spacecraft because it is
the only element that remains a gas in the extreme
cold necessary to maintain the liquid hydrogen
fuel used in many rockets and the Space
Shuttle. Liquid helium is used for cooling superconductive
magnets, used in magnetic resonance
imaging, and in magnetic separation. | | Production Methods | Helium is produced mostly by extraction from natural gas. The process involves cooling the stream of natural gas at sufficient low temperatures and high pressures to liquefy and separate all hydrocarbons, nitrogen and other gases from gaseous helium. The ‘crude’ helium gas may be purified further by repeated liquefaction of methane, nitrogen and other impurities under pressure. Trace hydrocarbons may be removed by adsorption on activated charcoal at liquid nitrogen temperature. Water may be removed by drying over a dehydrating agent such as bauxite. Carbon dioxide may be removed by passing helium through a scrubbing solution containing monoethanolamine-ethylene glycol or similar substances. Trace hydrogen may be removed from helium by converting it into water by mixing with oxygen and passing the mix over a palladium catalyst. Final purification may be achieved by adsorbing remaining trace contaminants over activated charcoal at liquid nitrogen temperature.
Alternatively, helium may be separated from natural gas by diffusion through permeable barriers, such as high silica glass or semipermeable membranes. The gas is supplied commercially in steel cylinders or tanks. The United States is the largest producer of helium in the world. | | Definition | Noble element of atomic number 2, first element
in the noble gas group of the periodic table, aw
4.00260, valence of 0. Helium nuclei are alpha particles. Most important isotope is helium-3. | | Definition | A colorless
monatomic gas; the first member of the
rare gases (group 18 of the periodic table).
Helium has the electronic configuration
1s2 and consists of a nucleus of two protons
and two neutrons (equivalent to an α-
particle) with two extra-nuclear electrons.
It has an extremely high ionization potential
and is completely resistant to chemical
attack of any sort. The gas accounts for
only 5.2 × 10-4% of the atmosphere; up to
7% occurs in some natural gas deposits.
Helium is the second most abundant element
in the universe, the primary process
on the Sun being nuclear fusion of hydrogen
to give helium.
Helium is recovered commercially from
natural gas in both the USA and countries
of the former USSR and it also forms part
of ammonia plant tail gas if natural gas is
used as a feedstock. Its applications are in
fields in which inertness is required and
where the cheaper alternatives, such as
nitrogen, are too reactive; for example,
high-temperature metallurgy, powder technology,
and as a coolant in nuclear reactors.
Helium is also favoured over nitrogen
for diluting oxygen for deep-sea diving
(lower solubility in blood) and as a pressurizer
for liquefied gas fuels in rockets
(total inertness). It is also used as an ideal
gas for balloons (no fire risk) and for lowtemperature
physics research.
Helium is unusual in that it is the only
known substance for which there is no
triple point (i.e., no combination of pressure
and temperature at which all three
phases can co-exist). This is because the interatomic
forces, which normally participate
in the formation of solids, are so weak
that they are of the same order as the zeropoint
energy. At 2.2 K helium undergoes a
transition from liquid helium I to liquid
helium II, the latter being a true liquid but
exhibiting superconductivity and an immeasurably
low viscosity (superfluidity).
The low viscosity allows the liquid to
spread in layers a few atoms thick, described
by some as ‘flowing uphill’.
Helium also has an isotope. 3He is
formed in nuclear reactions and by decay
of tritium. This also undergoes a phase
change at temperatures close to absolute
zero.
Symbol: He; m.p. 0.95 K (pressure);
b.p. 4.216 K; d. 0.1785 kg m-3 (0°C); p.n.
2; r.a.m. 4.002602. | | Definition | helium: Symbol He. A colourlessodourless gaseous nonmetallic elementbelonging to group 18 of theperiodic table ; a.n.2; r.a.m. 4.0026; d. 0.178 g dm–3; m.p.–272.2°C (at 20 atm.); b.p. –268.93°C.The element has the lowest boilingpoint of all substances and can be solidifiedonly under pressure. Naturalhelium is mostly helium–4, with asmall amount of helium–3. There arealso two short-lived radioactive isotopes:helium–5 and –6. It occurs inores of uranium and thorium and insome natural-gas deposits. It has a varietyof uses, including the provisionof inert atmospheres for welding andsemiconductor manufacture, as a refrigerantfor superconductors, and asa diluent in breathing apparatus. It isalso used in filling balloons. Chemicallyit is totally inert and has noknown compounds. It was discoveredin the solar spectrum in 1868 byJoseph Lockyer (1836–1920). | | General Description | A colorless, odorless, noncombustible gas. Can asphyxiate. Inhalation causes the voice to become squeaky (Mickey Mouse voice). Exposure of the container to prolonged heat or fire can cause HELIUM to rupture violently and rocket. If liquefied, contact of the very cold liquid with water causes violent boiling. Pressures may build to dangerous levels if the liquid contacts water in a closed container. Used in arc welding, to trace leaks in refrigeration and other closed systems and as a lifting gas for lighter-than-air aircraft. | | Reactivity Profile | Chemically inert. These substances undergo no chemical reactions under any known circumstances. They are nonflammable, noncombustible and nontoxic. They can asphyxiate. | | Hazard | Being inert, the noble gases are nontoxic. However, they can act as asphyxiant gases thatcan kill because of oxygen deprivations.
A possible hazard is when He++ nuclei, as alpha particles, are accelerated to high speeds andbombard a target. Alpha particles can be stopped by several inches of air or a piece of cardboard.As high-energy, charged particles generated from man-made or natural radioactivity,alpha particles can cause damage, but they are not as damaging to our bodies as are very shortwavelength gamma rays, which can only be stopped by lead shielding. | | Health Hazard | Vapors may cause dizziness or asphyxiation without warning. Vapors from liquefied gas are initially heavier than air and spread along ground. | | Fire Hazard | Non-flammable gases. Containers may explode when heated. Ruptured cylinders may rocket. | | Industrial uses | Helium is a colorless, odorless, elementary gas,He, with a specific gravity of 0.1368, liquefyingat –268.9°C, freezing at –272.2°C. It has avalency of zero and forms no electron-bondedcompounds. It has the highest ionization potentialof any element. The lifting power of heliumis only 92% that of hydrogen, but it is preferredfor balloons because it is inert and nonflammable,and is used in weather balloons. It is alsoused instead of air to inflate large tires for aircraftto save weight. Because of its low density,it is also used for diluting oxygen in the treatmentof respiratory diseases. Its heat conductivityis about six times that of air, and it is usedas a shielding gas in welding, and in vacuumtube and electric lamps. Because of its inertnesshelium can also be used to hold free chemicalradicals, which, when released, give highenergy and thrust for missile propulsion. Whenan electric current is passed through helium itgives a pinkish-violet light, and is thus used inadvertising signs. Helium can be obtained fromatmospheric nitrogen, but comes chiefly fromnatural gas. | | Materials Uses | Gaseous helium is noncorrosive and inert, and
may consequently be contained in systems constructed of any common metals and designed to
safely withstand the pressures involved. At the
temperature of liquid helium, ordinary carbon
steels and most alloy steels lose their ductility
and are considered unsafe for liquid helium
service. Satisfactory materials for use with liquid
helium include Type 18-8 stainless steel and
other austenitic nickel-chromium alloys, copper,
Monel, brass, and aluminum. | | Potential Exposure | It is used in weather balloons and in
welding gases. Liquid helium is used as a closed system
cooling agent. | | Physiological effects | Helium is nontoxic and inert. It can act as a
simple asphyxiant by diluting the concentration
of oxygen in air below levels necessary to support
life. Inhalation in excessive concentrations
can result in dizziness, nausea, vomiting, loss of
consciousness, and death. Death may result
from errors in judgment, confusion, or loss of
consciousness, which prevent self-rescue. At
low-oxygen concentrations, unconsciousness
and death may occur in seconds without warning. | | storage | Gaseous helium is commonly stored in high
pressure cylinders, hydril tubes, or tube trailers.
Liquid helium is commonly stored at the consumer
site in cryogenic liquid cylinders, portable
customer stations, and specially designed
insulated tanks. To minimize helium transfer losses, the shipping container for liquid helium
is normally used for storage. | | Shipping | UN1046 Helium, compressed, Hazard Class: 2.2;
Labels: 2.2-Nonflammable compressed gas; UN1963
Helium, refrigerated liquid (cryogenic liquid), Hazard
Class: 2.2; Labels: 2.2-Nonflammable compressed gas. | | Purification Methods | Dry the gas by passing it through a column of Linde 5A molecular sieves and CaSO4, then through an activated-charcoal trap cooled in liquid N2, to adsorb N2, argon, xenon and krypton. Also pass it over CuO pellets at 300o to remove hydrogen and hydrocarbons, over Ca chips at 600o to remove oxygen, and then over titanium chips at 700o to remove N2 [Arnold & Smith J Chem Soc, Faraday Trans 2 77 861 1981]. Its solubility in 100mL of H2O is 0.94mL at 25o, 1.05mL at 50o and 1.21 at 75o. | | Waste Disposal | Return refillable compressed
gas cylinders to supplier. | | GRADES AVAILABLE | CGA G-9.1, Commodity Specification
for Helium, presents the component
maxima, in parts per million (v/v) unless otherwise
shown, for specific grades of helium, also
known as quality verification levels (QVLs) [I].
A blank indicates no maximum limiting characteristic.
The absence of a value in a listed
QVL does not mean to imply that the limiting
characteristic is or is not present, but merely
indicates that the test is not required for compliance
with the specification. |
| | HELIUM Preparation Products And Raw materials |
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