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Ця стаття про the chemical element.

Шаблон:Infobox krypton Криптон (play [ˈkrɪptɒn] KRIP-ton; від [κρυπτός kryptos] помилка: {{lang-xx}}: текст вже має курсивний шрифт (допомога) "схований") — хімічний елемент із символом Kr і атомним номером 36. Належить до 18 і 4 періоду періодичної системи (головної підгрупи 8 групи 4 періоду, за старим варіантом періодичної системи). Безбарвний газ без запаху та смаку, інертний газ, криптон є у незначних кількостях у атмосфері, добувається фракційною перегонкою повітря,і часто використовується разом з іншими рідкісними газами у Люмінесцентних лампах. Криптон інертний для більшості практичних цілей.

Криптон, як і інші інертні гази, може використовуватись для освітлення при фотографуванні. Світло криптона містить велике число спектральних ліній, and krypton's high light output in plasmas allows it to play an important role in many high-powered gas lasers (krypton ion and excimer lasers), which pick out one of the many spectral lines to amplify. There is also a specific krypton fluoride laser. The high power and relative ease of operation of krypton discharge tubes caused (from 1960 to 1983) the official length of a meter to be defined in terms of the 605 nm (red-orange) spectral line of krypton-86.

Історія

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Сер Уільям Рамсей, відкривач криптону

Криптон було відкрито у Британії у 1898 році сером Уільямом Рамсеєм, шотландським хіміком, та Моррісом Траверсом, Англійським хіміком,в залишку, що залишається після випаровування майже усіх компонентів рідкого повітря. Неон було відкрито таким же методом Тими ж робітниками лише через декілька тижнів потому[1] William Ramsay was awarded the 1904 Nobel Prize in Chemistry for discovery of a series of noble gases, including krypton.

In 1960, an international agreement defined the meter in terms of wavelength of light emitted by the krypton-86 isotope (wavelength of 605.78 nanometers). This agreement replaced the longstanding standard meter located in Paris, which was a metal bar made of a platinum-iridium alloy (the bar was originally estimated to be one ten-millionth of a quadrant of the earth's polar circumference), and was itself replaced by a definition based on the speed of light — a fundamental physical constant. However, in 1927, the International Conference on Weights and Measures had redefined the meter in terms of a red cadmium spectral line (1 m = 1,553,164.13 wavelengths).[2] In October 1983, the same bureau defined the meter as the distance that light travels in a vacuum during 1/299,792,458 s.[3][4][5]

Характеристики

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Криптон характеризується кількома різкими лініями випромінювання(спектру) найяскравіші зелена та жовта.[6] It is one of the products of uranium fission.[7] Solidified krypton is white and crystalline with a face-centered cubic crystal structure, which is a common property of all noble gases (except helium, with a hexagonal close-packed crystal structure).

Ізотопи

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Докладніше: Ізотопи криптону

Криптон, що перебуває у природі сладається з 6-ти стабільних ізотопів. Також, близько 30 нестабільних ізотопів та iзомерів відомо.[8] 81Kr, продукт атмосферних реакцій,утворюється з інших природних ізотопів криптона. Будучи радіоактивним, його період піврозпаду складає 230,000 років. Krypton is highly volatile when it is near surface waters but 81Kr has been used for dating old (50,000–800,000 years) groundwater.[9]

85Kr — інертний радіоактивний газ з періодом піврозпаду 10.76 років. It is produced by the fission of uranium and plutonium, such as in nuclear bomb testing and nuclear reactors. 85Kr is released during the reprocessing of fuel rods from nuclear reactors. Concentrations at the North Pole are 30% higher than at the South Pole due to convective mixing.[10]

Хімія

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Як і інші інертні гази, криптон хімічно неактивний. However, following the first successful synthesis of xenon compounds in 1962, synthesis of krypton difluoride (KrF
2) was reported in 1963.[11] In the same year, KrF
4 was reported by Grosse, et al.,[12] but was subsequently shown to be a mistaken identification.[13] There are also unverified reports of a barium salt of a krypton oxoacid.[14] ArKr+ and KrH+ polyatomic ions have been investigated and there is evidence for KrXe or KrXe+.[15]

Compounds with krypton bonded to atoms other than fluorine have also been discovered. The reaction of KrF
2 with B(OTeF
5)
3 produces an unstable compound, Kr(OTeF
5)
2, that contains a krypton-oxygen bond. A krypton-nitrogen bond is found in the cation [HC≡N–Kr–F]+
, produced by the reaction of KrF
2 with [HC≡NH]+
[AsF−
6] below −50 °C.[16][17] HKrCN and HKrC≡CH (krypton hydride-cyanide and hydrokryptoacetylene) were reported to be stable up to 40 K.[11]

Natural occurrence

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The Earth has retained all of the noble gases that were present at its formation except for helium. Krypton's concentration in the atmosphere is about 1 ppm. It can be extracted from liquid air by fractional distillation.[18] The amount of krypton in space is uncertain, as the amount is derived from the meteoric activity and that from solar winds. The first measurements suggest an overabundance of krypton in space.[19]

Applications

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Krypton gas discharge tube
Krypton discharge (spectrum) tube

Krypton's multiple emission lines make ionized krypton gas discharges appear whitish, which in turn makes krypton-based bulbs useful in photography as a brilliant white light source. Krypton is thus used in some types of photographic flashes used in high speed photography. Krypton gas is also combined with other gases to make luminous signs that glow with a bright greenish-yellow light.[20]

Krypton mixes with argon as the fill gas of energy saving fluorescent lamps. This reduces their power consumption. Unfortunately this also reduces their light output and raises their cost.[21] Krypton costs about 100 times as much as argon. Krypton (along with xenon) is also used to fill incandescent lamps to reduce filament evaporation and allow higher operating temperatures to be used for the filament.[22] A brighter light results which contains more blue than conventional lamps.

Krypton's white discharge is often used to good effect in colored gas discharge tubes, which are then simply painted or stained in other ways to allow the desired color (for example, "neon" type advertising signs where the letters appear in differing colors are often entirely krypton-based). Krypton is also capable of much higher light power density than neon in the red spectral line region, and for this reason, red lasers for high-power laser light-shows are often krypton lasers with mirrors which select out the red spectral line for laser amplification and emission, rather than the more familiar helium-neon variety, which could never practically achieve the multi-watt red laser light outputs needed for this application.[23]

Krypton has an important role in production and usage of the krypton fluoride laser. The laser has been important in the nuclear fusion energy research community in confinement experiments. The laser has high beam uniformity, short wavelength, and the ability to modify the spot size to track an imploding pellet.[24]

In experimental particle physics, liquid krypton is used to construct quasi-homogeneous electromagnetic calorimeters. A notable example is the calorimeter of the NA48 experiment at CERN containing about 27 tonnes of liquid krypton. This usage is rare, since the cheaper liquid argon is typically used. The advantage of krypton over argon is a small Molière radius of 4.7 cm, which allows for excellent spatial resolution and low degree of overlapping. The other parameters relevant for calorimetry application are: radiation length of X0=4.7 cm, density of 2.4 g/cm3.

The sealed spark gap assemblies contained in ignition exciters used in some older jet engines contain a very small amount of Krypton-85 to obtain consistent ionization levels and uniform operation.

Krypton-83 has application in magnetic resonance imaging (MRI) for imaging airways. In particular, it may be used to distinguish between hydrophobic and hydrophilic surfaces containing an airway.[25]

Although xenon has potential for use in computed tomography (CT) to assess regional ventilation, its anesthetic properties limit its fraction in the breathing gas to 35%. The use of a breathing mixture containing 30% xenon and 30% krypton is comparable in effectiveness for CT to a 40% xenon fraction, while avoiding the unwanted effects of a high fraction xenon gas.[26]

Precautions

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Krypton is considered to be a non-toxic asphyxiant.[27] Krypton has a narcotic potency seven times greater than air, so breathing a gas containing 50% krypton and 50% air would cause narcosis similar to breathing air at four times atmospheric pressure. This would be comparable to scuba diving at a depth of 30 м (100 фут) (see nitrogen narcosis) and potentially could affect anyone breathing it. Nevertheless, that mixture would contain only 10% oxygen and hypoxia would be a greater concern.

Див. також

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Шаблон:Subject bar

Примітки

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  1. ↑ William Ramsay, Morris W. Travers (1898). On a New Constituent of Atmospheric Air. Proceedings of the Royal Society of London. 63 (1): 405—408. doi:10.1098/rspl.1898.0051.
  2. ↑ Burdun, G. D. (1958). On the new determination of the meter (pdf). Measurement Techniques. 1 (3): 259—264. doi:10.1007/BF00974680.
  3. ↑ Shri Krishna Kimothi (2002). The uncertainty of measurements: physical and chemical metrology: impact and analysis. American Society for Qualit. с. 122. ISBN 0-87389-535-5.
  4. ↑ Gibbs, Philip (1997). How is the speed of light measured?. Department of Mathematics, University of California. Процитовано 19 березня 2007.
  5. ↑ Unit of length (meter), NIST
  6. ↑ Spectra of Gas Discharges.
  7. ↑ Krypton (PDF). Argonne National Laboratory, EVS. 2005. Процитовано 17 березня 2007.
  8. ↑ Шаблон:RubberBible86th
  9. ↑ Thonnard, Norbert; Larry D. MeKay, Theodore C. Labotka (31). Development of Laser-Based Resonance Ionization Techniques for 81-Kr and 85-Kr Measurements in the Geosciences (PDF). University of Tennessee, Institute for Rare Isotope Measurements. с. 4—7. Процитовано 20 березня 2007.
  10. ↑ Resources on Isotopes. U.S. Geological Survey. Процитовано 20 березня 2007.
  11. ↑ а б Bartlett, Neil (2003). The Noble Gases. Chemical & Engineering News. Процитовано 2 липня 2006.
  12. ↑ DOI:10.1126/science.139.3559.1047
    Нема шаблону {{Cite doi/10.1126/science.139.3559.1047}}.заповнити вручну
  13. ↑ DOI:10.1007/BF01375764
    Нема шаблону {{Cite doi/10.1007/BF01375764}}.заповнити вручну
  14. ↑ DOI:10.1126/science.143.3603.242
    Нема шаблону {{Cite doi/10.1126/science.143.3603.242}}.заповнити вручну
  15. ↑ Periodic Table of the Elements (PDF). Los Alamos National Laboratory's Chemistry Division. с. 100—101. Архів оригіналу (PDF) за 25 листопада 2006. Процитовано 5 квітня 2007.
  16. ↑ John H. Holloway; Eric G. Hope (1998). A. G. Sykes (ред.). Advances in Inorganic Chemistry. Academic Press. с. 57. ISBN 0-12-023646-X.
  17. ↑ Errol G. Lewars (2008). Modeling Marvels: Computational Anticipation of Novel Molecules. Springer. с. 68. ISBN 1-4020-6972-3.
  18. ↑ How Products are Made: Krypton. Процитовано 2 липня 2006.
  19. ↑ Cardelli, Jason A.; Meyer, David M. (1996). The Abundance of Interstellar Krypton. The Astrophysical Journal Letters. The American Astronomical Society. с. L57—L60. Процитовано 5 квітня 2007.
  20. ↑ Mercury in Lighting (PDF). Cape Cod Cooperative Extension. Архів оригіналу (PDF) за 29 вересня 2007. Процитовано 20 березня 2007.
  21. ↑ "Energy-saving" lamps
  22. ↑ Properties, Applications and Uses of the "Rare Gases" Neon, Krypton and Xenon
  23. ↑ Laser Devices, Laser Shows and Effect (PDF). Процитовано 5 квітня 2007.
  24. ↑ Sethian, J.; M. Friedman, M.Myers. Krypton Fluoride Laser Development for Inertial Fusion Energy (PDF). Plasma Physics Division, Naval Research Laboratory. с. 1—8. Процитовано 20 березня 2007.
  25. ↑ Pavlovskaya, GE; Cleveland, ZI; Stupic, KF; Basaraba, RJ; Meersmann, T (2005). Hyperpolarized krypton-83 as a contrast agent for magnetic resonance imaging. Proceedings of the National Academy of Sciences U.S.A. 102 (51): 18275—9. Bibcode:2005PNAS..10218275P. doi:10.1073/pnas.0509419102. PMC 1317982. PMID 16344474.
  26. ↑ Chon, D; Beck, KC; Simon, BA; Shikata, H; Saba, OI; Hoffman, EA (2007). Effect of low-xenon and krypton supplementation on signal/noise of regional CT-based ventilation measurements. Journal of Applied Physiology. 102 (4): 1535—44. doi:10.1152/japplphysiol.01235.2005. PMID 17122371.
  27. ↑ Properties of Krypton

Further reading

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H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba * Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra ** Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
* La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
** Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr



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