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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 50.5 K (−368.77 °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 50.5 K (−368.77  °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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302 news items

Fri, 11 Jul 2014 15:30:00 -0700

GREENVILLE, Mich. (WOOD) – Hazmat crews are responding to a liquid oxygen leak at nursing home and rehabilitation center in Greenville. Belding Fire Department arrived at Metron of Greenville located at 828 E Washington Street responding to reports of ...

ExecutiveBiz (blog)

ExecutiveBiz (blog)
Tue, 08 Jul 2014 07:37:30 -0700

The company said Monday the agency uses nitrogen for pressurization, purging, inerting and pneumatic actuation, while oxygen is used as oxidizer for cryogenic rocket engines. The research and space flight centers included in the contract are Glenn ...
The Register Star
Thu, 24 Jul 2014 21:40:55 -0700

Route 9G was closed for more than four hours Thursday in Clermont when a truck carrying liquid oxygen became stuck in the roadway, according to the Columbia County Sheriff's Office. The tractor-trailer truck was traveling south on Route 9G at around 9 ...
Mon, 28 Jul 2014 08:22:30 -0700

Air Products has also developed a new patent pending technology for its medical liquid oxygen supply systems that can reduce the loss of normally vented oxygen by as much as 30 percent. The company's high efficiency supply system first pulls oxygen in ...


Tue, 29 Jul 2014 05:22:30 -0700

ATK also provided the large composite structures in the Delta IV core including the thermal shield that protects the RS-68 main engine during the boost phase, the centerbody between the liquid oxygen (LO2) and liquid hydrogen (LH2) tanks, the ...


Wed, 30 Jul 2014 09:41:15 -0700

This stage has twin tanks for the RP-1 (a highly refined form of Kerosene) and LOX (super cold liquid oxygen) propellants. The engine on the first stage is an Russian made RD-180 with twin combustion chambers. Also contained within the structure of the ...

Otago Daily Times

Network World
Tue, 29 Jul 2014 10:42:18 -0700

Electron will use liquid oxygen and kerosene that will fuel up nine of the company's Rutherford engines --named after the famous New Zealand scientist Ernest Rutherford – strapped together on Electron. With nine Rutherford engines on the first stage, ...
Tue, 29 Jul 2014 11:22:30 -0700

A single RL10B-2 engine delivers 24,750 pounds of thrust to power the upper stage, which is powered by cryogenic liquid hydrogen and liquid oxygen propellants. For more than 50 years, the RL10 has been one of the United States' most reliable ...

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