Editing Solvent (section)

==Safety==

===Fire===
Most organic solvents are [[flammable]] or highly flammable, depending on their [[volatility (chemistry)|volatility]]. Exceptions are some chlorinated solvents like [[dichloromethane]] and [[chloroform]]. Mixtures of solvent vapors and air can [[explosion|explode]]. Solvent vapors are heavier than air; they will sink to the bottom and can travel large distances nearly undiluted. Solvent vapors can also be found in supposedly empty drums and cans, posing a [[flash fire]] hazard; hence empty containers of volatile solvents should be stored open and upside down.

Both [[diethyl ether]] and [[carbon disulfide]] have exceptionally low [[autoignition temperature]]s which increase greatly the fire risk associated with these solvents. The autoignition temperature of carbon disulfide is below 100&nbsp;°C (212&nbsp;°F), so objects such as [[steam]] pipes, [[light bulb]]s, [[hotplate]]s, and recently extinguished [[bunsen burner]]s are able to ignite its vapors.

In addition some solvents, such as methanol, can burn with a very hot flame which can be nearly invisible under some lighting conditions.<ref>{{Cite book|last1=Fanick|first1=E. Robert|last2=Smith|first2=Lawrence R.|last3=Baines|first3=Thomas M. | name-list-style = vanc |date=1 October 1984|chapter=Safety Related Additives for Methanol Fuel|chapter-url=http://papers.sae.org/841378/ |publisher=SAE |location=Warrendale, PA|url-status=live|archive-url=https://web.archive.org/web/20170812062146/http://papers.sae.org/841378/|archive-date=12 August 2017|doi=10.4271/841378|title=SAE Technical Paper Series|volume=1}}</ref><ref>{{Cite journal| vauthors = Anderson JE, Magyarl MW, Siegl WO |date=1 July 1985|title=Concerning the Luminosity of Methanol-Hydrocarbon Diffusion Flames|journal=Combustion Science and Technology|volume=43|issue=3–4|pages=115–125|doi=10.1080/00102208508947000|issn=0010-2202}}</ref> This can delay or prevent the timely recognition of a dangerous fire, until flames spread to other materials.

===Explosive peroxide formation===
[[Ether]]s like [[diethyl ether]] and [[tetrahydrofuran]] (THF) can form highly explosive [[organic peroxide]]s upon exposure to oxygen and light. THF is normally more likely to form such peroxides than diethyl ether. One of the most susceptible solvents is [[diisopropyl ether]], but all ethers are considered to be potential peroxide sources.

The heteroatom ([[oxygen]]) stabilizes the formation of a [[free radical]] which is formed by the abstraction of a [[hydrogen]] atom by another free radical.{{clarify|date=March 2017}} The carbon-centered free radical thus formed is able to react with an oxygen molecule to form a peroxide compound. The process of peroxide formation is greatly accelerated by exposure to even low levels of light, but can proceed slowly even in dark conditions.

Unless a [[desiccant]] is used which can destroy the peroxides, they will concentrate during [[distillation]], due to their higher [[boiling point]]. When sufficient peroxides have formed, they can form a [[crystalline]], shock-sensitive solid [[precipitate]] at the mouth of a container or bottle. Minor mechanical disturbances, such as scraping the inside of a vessel, the dislodging of a deposit, or merely twisting the cap may provide sufficient energy for the peroxide to [[detonation|detonate]] or explode violently. 

Peroxide formation is not a significant problem when fresh solvents are used up quickly; they are more of a problem in laboratories which may take years to finish a single bottle. Low-volume users should acquire only small amounts of peroxide-prone solvents, and dispose of old solvents on a regular periodic schedule.

To avoid explosive peroxide formation, ethers should be stored in an airtight container, away from light, because both light and air can encourage peroxide formation.<ref>{{Cite web|url=https://www.uaf.edu/safety/industrial-hygiene/laboratory-safety/chem-gas/chemical-hazards/peroxides-ethers/|title=Peroxides and Ethers {{!}} Environmental Health, Safety and Risk Management|website=www.uaf.edu|language=en|access-date=25 January 2018}}</ref>

A number of tests can be used to detect the presence of a peroxide in an ether; one is to use a combination of [[iron(II) sulfate]] and [[potassium thiocyanate]]. The peroxide is able to [[oxidize]] the Fe<sup>2+</sup> ion to an Fe<sup>3+</sup> ion, which then forms a deep-red [[coordination complex]] with the [[thiocyanate]].

Peroxides may be removed by washing with acidic iron(II) sulfate, filtering through [[alumina]], or [[distillation|distilling]] from [[sodium]]/[[benzophenone]]. Alumina degrades the peroxides but some could remain intact in it, therefore it must be disposed of properly.<ref>{{Cite web|url=https://ehs.ucsc.edu/lab-safety-manual/specialty-chemicals/peroxide-formers.html#removalofperoxides |title=Handling of Peroxide Forming Chemicals |language=en|access-date=24 September 2021}}</ref> The advantage of using sodium/benzophenone is that [[moisture]] and oxygen are removed as well.<ref>{{Cite journal |last1=Inoue |first1=Ryo |last2=Yamaguchi |first2=Mana |last3=Murakami |first3=Yoshiaki |last4=Okano |first4=Kentaro |last5=Mori |first5=Atsunori |date=2018-10-31 |title=Revisiting of Benzophenone Ketyl Still: Use of a Sodium Dispersion for the Preparation of Anhydrous Solvents |journal=ACS Omega |language=en |volume=3 |issue=10 |pages=12703–12706 |doi=10.1021/acsomega.8b01707 |issn=2470-1343 |pmc=6210062 |pmid=30411016}}</ref>