Helium Chemische Eigenschaften,Einsatz,Produktion Methoden
ERSCHEINUNGSBILD
FARBLOSES, GERUCHLOSES, TIEFGEKüHLTES FLüSSIGGAS.
PHYSIKALISCHE GEFAHREN
Das Gas ist leichter als Luft.
ARBEITSPLATZGRENZWERTE
TLV: Erstickungsgefahr durch Sauerstoffverdr?ngung; (ACGIH 2005).
MAK nicht festgelegt (DFG 2005).
AUFNAHMEWEGE
Aufnahme in den K?rper durch Inhalation.
INHALATIONSGEFAHREN
Beim Entweichen aus dem Beh?lter kann das Gas die Luft verdr?ngen. Erstickungsgefahr in geschlossenen R?umen.
WIRKUNGEN BEI KURZZEITEXPOSITION
WIRKUNGEN BEI KURZZEITEXPOSITION: Die Flüssigkeit kann Erfrierungen hervorrufen. Erstickungsgefahr.
LECKAGE
Belüftung. Wasserstrahl NIEMALS auf die Flüssigkeit richten. Pers?nliche Schutzausrüstung: Umgebungsluftunabh?ngiges Atemschutzger?t.
S-S?tze Betriebsanweisung:
S9:Beh?lter an einem gut gelüfteten Ort aufbewahren.
Beschreibung
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.
Chemische Eigenschaften
Helium is a colorless, odorless, and tasteless
gas. It is nonflammable.
Physikalische Eigenschaften
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/cm
3.
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.
Charakteristisch
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.
Verwenden
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.
Vorbereitung Methode
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.
Allgemeine Beschreibung
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.
Reaktivit?t anzeigen
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.
Brandgefahr
Non-flammable gases. Containers may explode when heated. Ruptured cylinders may rocket.
Industrielle Verwendung
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.
m?gliche Exposition
It is used in weather balloons and in
welding gases. Liquid helium is used as a closed system
cooling agent.
Lager
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.
Versand/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.
l?uterung methode
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.
Helium Upstream-Materialien And Downstream Produkte
Upstream-Materialien
Downstream Produkte
