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This article is about the liquid form of the element oxygen. For the commercial dietary supplement product, see Liquid Oxygen (supplement).
"LOX" redirects here. For other uses, see Lox (disambiguation).
Liquid oxygen
Molecular formula O2
Molar mass 32.00 g mol−1
Appearance Pale blue liquid
Density 1.141 g·cm−3
Melting point 54.36 K (−361.82 °F; −222.65 °C)
Boiling point 90.19 K (−297.33 °F, −182.96 °C)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Liquid oxygen — abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries — is one of the physical forms of elemental oxygen.

Physical properties[edit]

The blue color of liquid oxygen in a dewar flask

Liquid oxygen has a pale blue color and is strongly paramagnetic; it can be suspended between the poles of a powerful horseshoe magnet.[1] Liquid oxygen has a density of 1.141 g/cm3 (1.141 kg/L or 1141 kg/m3) and is cryogenic with a freezing point of 54.36 K (−361.82  °F, −222.65 °C) and a boiling point of 90.19 K (−297.33 °F, −182.96 °C) at 101.325 kPa (760 mmHg). Liquid oxygen has an expansion ratio of 1:861 under 1 standard atmosphere (100 kPa) and 20 °C (68 °F),[2][3] and because of this, it is used in some commercial and military aircraft as transportable source of breathing oxygen.

Because of its cryogenic nature, liquid oxygen can cause the materials it touches to become extremely brittle. Liquid oxygen is also a very powerful oxidizing agent: organic materials will burn rapidly and energetically in liquid oxygen. Further, if soaked in liquid oxygen, some materials such as coal briquettes, carbon black, etc., can detonate unpredictably from sources of ignition such as flames, sparks or impact from light blows. Petrochemicals, including asphalt, often exhibit this behavior.

The tetraoxygen molecule (O4) was first predicted in 1924 by Gilbert N. Lewis, who proposed it to explain why liquid oxygen defied Curie's law.[4] Modern computer simulations indicate that although there are no stable O4 molecules in liquid oxygen, O2 molecules do tend to associate in pairs with antiparallel spins, forming transient O4 units.[5]

Liquid nitrogen has a lower boiling point at −196 °C (77 K) than oxygen's −183 °C (90 K), and vessels containing liquid nitrogen can condense oxygen from air: when most of the nitrogen has evaporated from such a vessel there is a risk that liquid oxygen remaining can react violently with organic material. Conversely, liquid nitrogen or liquid air can be oxygen-enriched by letting it stand in open air; atmospheric oxygen dissolves in it, while nitrogen evaporates preferentially.


In commerce, liquid oxygen is classified as an industrial gas and is widely used for industrial and medical purposes. Liquid oxygen is obtained from the oxygen found naturally in air by fractional distillation in a cryogenic air separation plant.

Liquid oxygen is a common cryogenic liquid oxidizer propellant for spacecraft rocket applications, usually in combination with liquid hydrogen, kerosene or methane.[6][7] Liquid oxygen is useful in this role because it creates a high specific impulse.[citation needed] It was used in the very first rocket applications like the V2 missile (under the name A-Stoff and Sauerstoff) and Redstone, R-7 Semyorka, Atlas boosters, and the ascent stages of the Apollo Saturn rockets. Liquid oxygen was also used in some early ICBMs, although more modern ICBMs do not use liquid oxygen because its cryogenic properties and need for regular replenishment to replace boiloff make it harder to maintain and launch quickly. Many modern rockets use liquid oxygen, including the main engines on the now-retired Space Shuttle.

Liquid oxygen also had extensive use in making oxyliquit explosives, but is rarely used now due to a high rate of accidents.[citation needed]

It is also used in the activated sludge process in waste water treatment to maintain a high level of micro-organisms.[citation needed]

Portable container for transport of liquid oxygen


See also[edit]


  1. ^ John W. Moore; Conrad L. Stanitski; Peter C. Jurs (21 January 2009). Principles of Chemistry: The Molecular Science. Cengage Learning. pp. 297–. ISBN 978-0-495-39079-4. Retrieved 3 April 2011. 
  2. ^ Cryogenic Safety. chemistry.ohio-state.edu.
  3. ^ Characteristics. Lindecanada.com. Retrieved on 2012-07-22.
  4. ^ Lewis, Gilbert N. (1924). "The Magnetism of Oxygen and the Molecule O2". Journal of the American Chemical Society 46 (9): 2027–2032. doi:10.1021/ja01674a008. 
  5. ^ Oda, Tatsuki; Alfredo Pasquarello (2004). "Noncollinear magnetism in liquid oxygen: A first-principles molecular dynamics study". Physical Review B 70 (134402): 1–19. Bibcode:2004PhRvB..70m4402O. doi:10.1103/PhysRevB.70.134402. 
  6. ^ Todd, David (November 20, 2012). "Musk goes for methane-burning reusable rockets as step to colonise Mars". FlightGlobal Hyperbola. Retrieved November 22, 2012. ""We are going to do methane." Musk announced as he described his future plans for reusable launch vehicles including those designed to take astronauts to Mars within 15 years, "The energy cost of methane is the lowest and it has a slight Isp (Specific Impulse) advantage over Kerosene" said Musk adding, "And it does not have the pain in the ass factor that hydrogen has". ... "SpaceX's initial plan will be to build a lox/methane rocket for a future upper stage codenamed Raptor. ... The new Raptor upper stage engine is likely to be only the first engine in a series of lox/methane engines. ... "." 
  7. ^ Belluscio, Alejandro G. (March 7, 2014). "SpaceX advances drive for Mars rocket via Raptor power". NASAspaceflight.com. Retrieved March 13, 2014. 
  8. ^ Cryogenics. Scienceclarified.com. Retrieved on 2012-07-22.

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Liquid_oxygen — Please support Wikipedia.
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164 news items


Thu, 21 Aug 2014 16:10:08 -0700

(WBIR-Sevier County) A lightning strike hit near a liquid oxygen tank about a quarter of a mile from Douglas Dam in Sevier County Wednesday night. TVA spokesperson, Travis Brickey, said the fire occurred on the oxygen tanks' lines. He said the tanks ...
Times of India
Sun, 10 Aug 2014 00:03:14 -0700

SURAT: In an executive committee meeting of Surat Municipal Corporation (SMC) run SMIMER hospital, it was decided to increase facilities including liquid Oxygen tank. SMC runs this hospital for the needy and un affording patients of the city and more ...

Space Fellowship

Space Fellowship
Tue, 12 Aug 2014 02:00:00 -0700

A full-scale replica of the SLS liquid oxygen tank feed system — which will be housed in the rocket's core stage — is set up on one of Marshall's test stands to show that proven procedures will keep the tank's thousands of gallons of oxidizer from ...

Financial Express

Tue, 05 Aug 2014 06:52:30 -0700

Beyond breathable O2, a MOXIE like system could also produce the liquid oxygen needed to fuel rockets bound for an Earth return. Unlike fuel cells designed to work here on Earth MOXIE will be a “fuel cell run in reverse,” says Michael Hecht, MOXIE's ...

Controlled Environments Magazine

Florida Today
Tue, 02 Sep 2014 03:52:30 -0700

There's also interest in mining asteroids for metals, rare minerals and frozen water, which could be converted into liquid oxygen and liquid hydrogen for rocket fuel that would make a trip to Mars easier and cheaper. Q: Why is there interest in ...
Tue, 02 Sep 2014 13:37:30 -0700

Lockheed was the prime contractor for the huge external fuel tank, which was used to store liquid oxygen and liquid hydrogen for the space shuttle launch system, the previous version of the SLS. The company also is the supplier for the new manned NASA ...
Florida Today
Mon, 01 Sep 2014 21:11:09 -0700

There's also interest in mining asteroids for metals, rare minerals and frozen water, which could be converted into liquid oxygen and liquid hydrogen for rocket fuel that would make a trip to Mars easier and cheaper. Q: Why is there interest in ...

Pakistan Today

Pakistan Today
Mon, 11 Aug 2014 13:14:40 -0700

The situation arose when Services Hospital Medical Superintendent (MS) Dr Rehana Malik wrote a letter to the deputy inspector general (DIG) operations requesting him to allow the vehicle carrying liquid oxygen to enter as it was not being delivered due ...

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