Liquid oxygen

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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
IUPAC name

Liquid oxygen

Other names

LOX, LOx, Lox

Properties
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
The blue color of liquid oxygen in a dewar flask
Portable container for transport of liquid oxygen

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

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) 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.

Uses

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 or kerosene. Liquid oxygen is useful in this role because it creates a high specific impulse. 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.

It is also be used in activated sludge process in waste water treatment to maintain a high level of micro-organisms.

History

See also

References

  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. ↑ Cryogenics. Scienceclarified.com. Retrieved on 2012-07-22.
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