Editing Liquid oxygen (section)

==Physical properties==
Liquid oxygen has a clear [[cyan]] color and is strongly [[paramagnetism|paramagnetic]]: it can be suspended between the poles of a powerful [[horseshoe magnet]].<ref>{{cite book |author1=Moore, John W. |author2=Stanitski, Conrad L. |author3=Jurs, Peter C. |title=Principles of Chemistry: The Molecular Science |url=https://books.google.com/books?id=ZOm8L9oCwLMC&pg=PA297 |access-date=3 April 2011 |date=21 January 2009 |publisher=Cengage Learning |isbn=978-0-495-39079-4 |pages=297–}}</ref> Liquid oxygen has a density of {{convert|1.141|kg/L|abbr=on|g/ml}}, slightly denser than liquid water, and is [[cryogenics|cryogenic]] with a freezing point of {{convert|54.36|K|abbr=on}} and a boiling point of {{convert|90.19|K|abbr=on}} at {{convert|1|bar|psi|abbr=on|1}}. Liquid oxygen has an [[expansion ratio]] of 1:861<ref>[https://web.archive.org/web/20080607160832/http://www.chemistry.ohio-state.edu/ehs/handbook/gases/cryosafe.htm Cryogenic Safety]. chemistry.ohio-state.edu.</ref><ref>[http://www.lindecanada.com/en/aboutboc/safety/cryogenic_liquids/characteristics.php Characteristics]. {{webarchive|url=https://web.archive.org/web/20120218125124/http://www.lindecanada.com/en/aboutboc/safety/cryogenic_liquids/characteristics.php |date=2012-02-18 }}. Lindecanada.com. Retrieved on 2012-07-22.</ref> and because of this, it is used in some commercial and military aircraft as a transportable source of breathing oxygen.{{Citation needed|date=March 2025}}

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 [[Oxyliquit|soaked in liquid oxygen]], some materials such as coal briquettes, [[carbon black]], etc., can [[Detonation|detonate]] unpredictably from sources of ignition such as flames, sparks or impact from light blows. [[Petrochemical]]s, including [[Bitumen|asphalt]], often exhibit this behavior.<ref>{{cite web |url=https://archive.org/details/23004LiquidOxygenReceiptTransferStorageDisposal |title=Liquid Oxygen Receipt, Handling, Storage and Disposal |publisher=USAF Training Film }}</ref>

The [[tetraoxygen]] molecule (O<sub>4</sub>) was predicted in 1924 by [[Gilbert N. Lewis]], who proposed it to explain why liquid oxygen defied [[Curie's law]].<ref>{{cite journal
|last = Lewis
|first = Gilbert N.
|author-link = Gilbert N. Lewis
|year = 1924
|title = The Magnetism of Oxygen and the Molecule O<sub>2</sub>
|journal = Journal of the American Chemical Society
|volume = 46
|issue = 9
|pages = 2027–2032
|doi = 10.1021/ja01674a008
}}</ref> Modern computer simulations indicate that, although there are no stable O<sub>4</sub> molecules in liquid oxygen, O<sub>2</sub> molecules do tend to associate in pairs with antiparallel [[Spin (physics)|spins]], forming transient O<sub>4</sub> units.<ref>{{cite journal
|last = Oda
|first = Tatsuki
|author2 = Alfredo Pasquarello
|year = 2004
|title = Noncollinear magnetism in liquid oxygen: A first-principles molecular dynamics study
|journal = Physical Review B
|volume = 70
|issue = 134402
|pages = 1–19
|doi = 10.1103/PhysRevB.70.134402
|bibcode = 2004PhRvB..70m4402O
|hdl = 2297/3462
|s2cid = 123535786
|url = https://kanazawa-u.repo.nii.ac.jp/?action=repository_uri&item_id=10177
|hdl-access = free
}}</ref>

[[Liquid nitrogen]] has a lower boiling point at −196&nbsp;°C (77&nbsp;K) than oxygen's −183&nbsp;°C (90&nbsp;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.{{Citation needed|date=March 2025}}

The [[surface tension]] of liquid oxygen at its normal pressure boiling point is {{convert|13.2|dyn/cm|mN/m|abbr=on}}.<ref>J. M. Jurns and J. W. Hartwig (2011). [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110014531.pdf Liquid Oxygen Liquid Acquisition Device Bubble Point Tests With High Pressure LOX at Elevated Temperatures], p. 4.</ref>