Editing Chlorine (section)

==Applications==
[[File:Tank_car_with_placard_1017_(chlorine).jpg|thumb|A railway [[tank car]] carrying chlorine, displaying [[hazardous materials]] information including a diamond-shaped [[Placard#United States Department of Transportation|U.S. DOT placard]] showing a [[UN number]]<ref name=":0">{{Cite web |last=Beaucham |first=Catherine C. |date=August 2023 |title=Evaluation of Potential Exposures to Railway Hazardous Material Inspectors |url=https://www.cdc.gov/niosh/hhe/reports/pdfs/2022-0049-3387.pdf |access-date=2024-05-04 |website=U.S. National Institute for Occupational Safety and Health |type=[[Health Hazard Evaluation Program|Health Hazard Evaluation Report]]}}</ref>]]
Sodium chloride is the most common chlorine compound, and is the main source of chlorine for the demand by the chemical industry. About 15000 chlorine-containing compounds are commercially traded, including such diverse compounds as chlorinated [[methane]], [[ethane]]s, [[vinyl chloride]], [[polyvinyl chloride]] (PVC), [[aluminium trichloride]] for [[catalysis]], the chlorides of [[magnesium]], [[titanium]], [[zirconium]], and [[hafnium]] which are the precursors for producing the pure form of those elements.<ref name="Greenwood792" />

Quantitatively, of all elemental chlorine produced, about 63% is used in the manufacture of organic compounds, and 18% in the manufacture of inorganic chlorine compounds.{{sfn|Greenwood|Earnshaw|1997|p=798}} About 15,000 chlorine compounds are used commercially.{{sfn|Greenwood|Earnshaw|1997|p=793}} The remaining 19% of chlorine produced is used for bleaches and disinfection products.<ref name="Greenwood796" /> The most significant of organic compounds in terms of production volume are [[1,2-dichloroethane]] and [[vinyl chloride]], intermediates in the production of [[Polyvinyl chloride|PVC]]. Other particularly important organochlorines are [[methyl chloride]], [[methylene chloride]], [[chloroform]], [[vinylidene chloride]], [[trichloroethylene]], [[perchloroethylene]], [[allyl chloride]], [[epichlorohydrin]], [[chlorobenzene]], [[dichlorobenzene]]s, and [[trichlorobenzene]]s. The major inorganic compounds include HCl, Cl<sub>2</sub>O, HOCl, NaClO<sub>3</sub>, [[aluminium chloride|AlCl<sub>3</sub>]], [[silicon tetrachloride|SiCl<sub>4</sub>]], [[tin(IV) chloride|SnCl<sub>4</sub>]], [[phosphorus trichloride|PCl<sub>3</sub>]], [[phosphorus pentachloride|PCl<sub>5</sub>]], [[phosphoryl chloride|POCl<sub>3</sub>]], [[arsenic trichloride|AsCl<sub>3</sub>]], [[antimony trichloride|SbCl<sub>3</sub>]], [[Antimony pentachloride|SbCl<sub>5</sub>]], [[Bismuth chloride|BiCl<sub>3</sub>]], and [[zinc chloride|ZnCl<sub>2</sub>]].<ref name="Greenwood796" />

=== Sanitation, disinfection, and antisepsis ===
{{Main|Water chlorination|Bleach}}

==== Combating putrefaction ====

In France (as elsewhere), [[Catgut|animal intestines]] were processed to make musical instrument strings, [[Goldbeater's skin]] and other products. This was done in "gut factories" (''boyauderies''), and it was an odiferous and unhealthy process. In or about 1820, the [[Société d'encouragement pour l'industrie nationale]] offered a prize for the discovery of a method, chemical or mechanical, for separating the [[Peritoneum|peritoneal]] membrane of animal intestines without [[putrefaction]].<ref name="nbu" /><ref name="knight">{{cite book |author=Knight, Charles |page=427 |title=Arts and sciences |volume=1 |publisher=Bradbury, Evans & Co. |date=1867}}</ref> The prize was won by [[Antoine-Germain Labarraque]], a 44-year-old French chemist and pharmacist who had discovered that Berthollet's chlorinated bleaching solutions ("''[[Javel water|Eau de Javel]]''") not only destroyed the smell of putrefaction of animal tissue decomposition, but also actually retarded the decomposition.<ref name="knight" /><ref name="bouvet" />

Labarraque's research resulted in the use of chlorides and hypochlorites of lime ([[calcium hypochlorite]]) and of sodium ([[sodium hypochlorite]]) in the ''boyauderies.'' The same chemicals were found to be useful in the routine [[Disinfectant|disinfection]] and deodorization of [[latrine]]s, [[sewerage|sewers]], markets, [[abattoir]]s, [[anatomical theatre]]s, and morgues.<ref name="gedeon">{{cite book |author=Gédéon, Andras |url=https://books.google.com/books?id=vw9qq7Ghjp4C |title=Science and technology in medicine |publisher=Springer |date=2006 |pages=181–82 |isbn=978-0-387-27874-2 |url-status=live |archive-url=https://web.archive.org/web/20151231220856/https://books.google.com/books?id=vw9qq7Ghjp4C&printsec=frontcover |archive-date=2015-12-31 }}</ref> They were successful in [[hospital]]s, [[Lazaretto|lazarets]], [[prison]]s, [[Hospital|infirmaries]] (both on land and at sea), [[Magnanery|magnaneries]], [[stable]]s, cattle-sheds, etc.; and they were beneficial during [[exhumation]]s,<ref>{{cite book |title=On the disinfecting properties of Labarraque's preparations of chlorine |author=Labarraque, Antoine Germain |others=Translated by James Scott |date=1828 |page=8 |url=https://books.google.com/books?id=pD0XAQAAMAAJ |url-status=live |archive-url=https://web.archive.org/web/20151231220856/https://books.google.com/books?id=pD0XAQAAMAAJ&printsec=frontcover |archive-date=2015-12-31 }}</ref> [[embalming]], outbreaks of epidemic disease, fever, and [[Blackleg (disease)|blackleg]] in cattle.<ref name="nbu">{{cite book |editor=Hoefer, Jean Chrétien Ferdinand |contribution=Labarraque, Antoine-Germain |title=Nouvelle biographie universelle |volume=28 |pages=323–24 |ol=24229911M }}</ref>

==== Disinfection ====
Labarraque's chlorinated lime and soda solutions have been advocated since 1828 to prevent infection (called "contagious infection", presumed to be transmitted by "[[miasma theory of disease|miasmas]]"), and to treat [[putrefaction]] of existing wounds, including septic wounds.<ref>Scott, James (trans.). ''[https://books.google.com/books?id=pD0XAQAAMAAJ On the disinfecting properties of Labarraque's preparations of chlorine]'' {{webarchive|url=https://web.archive.org/web/20151231220856/https://books.google.com/books?id=pD0XAQAAMAAJ&printsec=frontcover |date=2015-12-31 }} (S. Highley, 1828) Accessed Nov 1, 2011.</ref> In his 1828 work, Labarraque recommended that doctors breathe chlorine, wash their hands in chlorinated lime, and even sprinkle chlorinated lime about the patients' beds in cases of "contagious infection". In 1828, the contagion of infections was well known, even though the agency of the [[Microorganism|microbe]] was not discovered until more than half a century later.

During the [[1832 cholera epidemic|Paris cholera outbreak]] of 1832, large quantities of so-called ''chloride of lime'' were used to disinfect the capital. This was not simply modern [[calcium chloride]], but chlorine gas dissolved in lime-water (dilute [[calcium hydroxide]]) to form [[calcium hypochlorite]] (chlorinated lime). Labarraque's discovery helped to remove the terrible stench of decay from hospitals and dissecting rooms, and by doing so, effectively deodorised the [[Latin Quarter, Paris|Latin Quarter]] of Paris.<ref name="corbin">Corbin, Alain (1988). ''[https://books.google.com/books?id=LI1M4sLcvPAC The Foul and the Fragrant: Odor and the French Social Imagination]''. {{webarchive|url=https://web.archive.org/web/20151231220856/https://books.google.com/books?id=LI1M4sLcvPAC&printsec=frontcover |date=2015-12-31 }}. Harvard University Press. pp. 121–22.</ref> These "putrid miasmas" were thought by many to cause the spread of "contagion" and "infection" – both words used before the germ theory of infection. Chloride of lime was used for destroying odors and "putrid matter". One source claims chloride of lime was used by Dr. John Snow to disinfect water from the cholera-contaminated well that was feeding the Broad Street pump in 1854 London,<ref>{{cite book|publisher=Wiley|year=2010|chapter-url=http://samples.sainsburysebooks.co.uk/9780470561324_sample_411014.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://samples.sainsburysebooks.co.uk/9780470561324_sample_411014.pdf |archive-date=2022-10-09 |url-status=live|title=White's Handbook of Chlorination and Alternative Disinfectants|place=Hoboken, NJ|page=452|author=Lewis, Kenneth A.|doi=10.1002/9780470561331.ch9|isbn=978-0-470-56133-1|chapter=Ch. 9 Hypochlorination – Sodium Hypochlorite}}{{dead link|date=December 2017 |bot=KAP03 |fix-attempted=yes }}</ref> though three other reputable sources that describe that famous cholera epidemic do not mention the incident.<ref name="Vinten">Vinten-Johansen, Peter, Howard Brody, Nigel Paneth, Stephen Rachman and Michael Rip. (2003). ''Cholera, Chloroform, and the Science of Medicine''. New York:Oxford University.</ref><ref>Hemphill, Sandra. (2007). ''The Strange Case of the Broad Street Pump: John Snow and the Mystery of Cholera''. Los Angeles:University of California</ref><ref>[[Steven Johnson (author)|Johnson, Steven]]. (2006). ''[[The Ghost Map: The Story of London's Most Terrifying Epidemic and How It Changed Science, Cities, and the Modern World]]''. New York :Riverhead Books</ref> One reference makes it clear that chloride of lime was used to disinfect the [[offal]] and filth in the streets surrounding the Broad Street pump – a common practice in mid-nineteenth century England.<ref name="Vinten" />{{rp|296}}

==== Semmelweis and experiments with antisepsis ====
[[File:Semmelweis Ignác.jpg|thumb|[[Ignaz Semmelweis]]|left|upright=0.6 ]]
Perhaps the most famous application of Labarraque's chlorine and [[base (chemistry)|chemical base]] solutions was in 1847, when [[Ignaz Semmelweis]] used chlorine-water (chlorine dissolved in pure water, which was cheaper than chlorinated lime solutions) to disinfect the hands of Austrian doctors, which Semmelweis noticed still carried the stench of decomposition from the dissection rooms to the patient examination rooms. Long before the germ theory of disease, Semmelweis theorized that "cadaveric particles" were transmitting decay from fresh medical cadavers to living patients, and he used the well-known "Labarraque's solutions" as the only known method to remove the smell of decay and tissue decomposition (which he found that soap did not). The solutions proved to be far more effective antiseptics than soap (Semmelweis was also aware of their greater efficacy, but not the reason), and this resulted in Semmelweis's celebrated success in stopping the transmission of [[childbed fever]] ("puerperal fever") in the maternity wards of [[Vienna General Hospital]] in [[Austria]] in 1847.<ref>{{cite web|url=http://www.americanchemistry.com/s_chlorine/sec_content.asp?CID=1166&DID=4476&CTYPEID=109 |title=Chlorine Story |publisher=americanchemistry |access-date=2008-07-10 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20110429214443/http://www.americanchemistry.com/s_chlorine/sec_content.asp?CID=1166&DID=4476&CTYPEID=109 |archive-date=2011-04-29 }}</ref>

Much later, during World War I in 1916, a standardized and diluted modification of Labarraque's solution containing hypochlorite (0.5%) and boric acid as an acidic stabilizer was developed by [[Henry Drysdale Dakin]] (who gave full credit to Labarraque's prior work in this area). Called [[Dakin's solution]], the method of wound irrigation with chlorinated solutions allowed antiseptic treatment of a wide variety of open wounds, long before the modern antibiotic era. A modified version of this solution continues to be employed in wound irrigation in modern times, where it remains effective against bacteria that are resistant to multiple antibiotics (see [[Century Pharmaceuticals]]).<ref>{{Cite journal | last1 = Rezayat | first1 = C. | last2 = Widmann | first2 = W. D. | last3 = Hardy | first3 = M. A. | doi = 10.1016/j.cursur.2006.04.009 | title = Henry Drysdale Dakin: More Than His Solution | journal = Current Surgery | volume = 63 | issue = 3 | pages = 194–96 | year = 2006 | pmid = 16757372}}</ref>
{{clear}}

==== Public sanitation ====
[[File:Mosul-swimming.jpg|thumb|Chlorinated water is used in [[swimming pools]] to disinfect water from microbial contaminants]]
[[File:Liquid Pool Chlorine.jpg|thumb|Liquid pool chlorine]]

The first continuous application of chlorination to drinking U.S. water was installed in [[Jersey City]], New Jersey, in 1908.<ref>Joseph Cotruvo, Victor Kimm, Arden Calvert. [http://www.epaalumni.org/hcp/drinkingwater.pdf "Drinking Water: A Half Century of Progress."] {{Webarchive|url=https://web.archive.org/web/20200731153608/http://www.epaalumni.org/hcp/drinkingwater.pdf |date=2020-07-31 }} EPA Alumni Association. March 1, 2016.</ref> By 1918, the [[US Department of Treasury]] called for all drinking water to be disinfected with chlorine. Chlorine is presently an important chemical for [[water purification]] (such as in water treatment plants), in [[disinfectant]]s, and in [[bleach]]. Even small water supplies are now routinely chlorinated.<ref name="CRC">{{cite book| author = Hammond, C. R.|title = The Elements, in Handbook of Chemistry and Physics|edition = 81st| publisher =CRC press| date = 2000| isbn = 978-0-8493-0481-1}}</ref>

Chlorine is usually used (in the form of [[hypochlorous acid]]) to kill [[bacteria]] and other microbes in [[drinking water]] supplies and public swimming pools. In most private swimming pools, chlorine itself is not used, but rather [[sodium hypochlorite]], formed from chlorine and [[sodium hydroxide]], or solid tablets of chlorinated isocyanurates. The drawback of using chlorine in swimming pools is that the chlorine reacts with the [[amino acid]]s in proteins in human hair and skin. Contrary to popular belief, the distinctive "chlorine aroma" associated with swimming pools is not the result of elemental chlorine itself, but of [[monochloramine|chloramine]], a chemical compound produced by the reaction of free dissolved chlorine with amines in organic substances including those in urine and sweat.<ref>{{cite web|title=Chloramines & Pool Operation|url=https://www.cdc.gov/healthywater/swimming/aquatics-professionals/chloramines.html|access-date=13 March 2022|publisher=Centres for Disease Control and Prevention|archive-date=13 March 2022|archive-url=https://web.archive.org/web/20220313130646/https://www.cdc.gov/healthywater/swimming/aquatics-professionals/chloramines.html|url-status=live}}</ref> As a disinfectant in water, chlorine is more than three times as effective against ''[[Escherichia coli]]'' as [[bromine]], and more than six times as effective as [[iodine]].<ref>{{cite journal|author=Koski T. A. |author2=Stuart L. S. |author3=Ortenzio L. F.|title=Comparison of chlorine, bromine, iodine as disinfectants for swimming pool water|journal = Applied Microbiology|volume = 14|issue = 2|date = 1966|pages = 276–79|pmid=4959984|pmc=546668|doi=10.1128/AEM.14.2.276-279.1966 }}</ref> Increasingly, [[monochloramine]] itself is being directly added to drinking water for purposes of disinfection, a process known as [[chloramination]].{{r|CDC-Chloramination}}

It is often impractical to store and use poisonous chlorine gas for water treatment, so alternative methods of adding chlorine are used. These include [[hypochlorite]] solutions, which gradually release chlorine into the water, and compounds like [[sodium dichloro-s-triazinetrione]] (dihydrate or anhydrous), sometimes referred to as "dichlor", and [[trichloro-s-triazinetrione]], sometimes referred to as "trichlor". These compounds are stable while solid and may be used in powdered, granular, or tablet form. When added in small amounts to pool water or industrial water systems, the chlorine atoms hydrolyze from the rest of the molecule, forming hypochlorous acid (HOCl), which acts as a general [[biocide]], killing germs, microorganisms, algae, and so on.{{sfn|Greenwood|Earnshaw|1997|p=860}}<ref>{{Holleman&Wiberg|page=411}}</ref>

=== Use as a weapon ===

==== World War I ====
{{Main|Chemical weapons in World War I}}

Chlorine gas, also known as bertholite, was first [[chemical warfare|used as a weapon]] in [[World War I]] by Germany on April 22, 1915, in the [[Second Battle of Ypres]].<ref>"Battle of Ypres" ''The Canadian Encyclopedia''</ref><ref name="CEN2015">{{cite journal | first = Sarah | last = Everts | url = http://chemicalweapons.cenmag.org/when-chemicals-became-weapons-of-war/ | title = When Chemicals Became Weapons of War | journal = Chemical & Engineering News | volume = 93 | issue = 8 | date = February 23, 2015 | url-status = live | archive-url = https://web.archive.org/web/20160330203223/http://chemicalweapons.cenmag.org/when-chemicals-became-weapons-of-war/ | archive-date = March 30, 2016 }}</ref> As described by the soldiers, it had the distinctive smell of a mixture of pepper and pineapple.<ref>{{Cite web |last=Patton |first=James |title=Gas in The Great War |url=https://www.kumc.edu/school-of-medicine/academics/departments/history-and-philosophy-of-medicine/archives/wwi/essays/medicine/gas-in-the-great-war.html |url-status=live |archive-url=https://web.archive.org/web/20240615142532/https://www.kumc.edu/school-of-medicine/academics/departments/history-and-philosophy-of-medicine/archives/wwi/essays/medicine/gas-in-the-great-war.html |archive-date=15 June 2024 |access-date=2024-06-21 |website=KU Medical Center |language=en-us}}</ref> It also tasted metallic and stung the back of the throat and chest. Chlorine reacts with water in the [[Mucous membrane|mucosa]] of the lungs to form [[hydrochloric acid]], destructive to living tissue and potentially lethal. Human respiratory systems can be protected from chlorine gas by [[gas mask]]s with [[activated charcoal]] or other filters, which makes chlorine gas much less lethal than other chemical weapons. It was pioneered by a German scientist later to be a Nobel laureate, [[Fritz Haber]] of the [[Kaiser Wilhelm Institute for Chemistry|Kaiser Wilhelm Institute]] in Berlin, in collaboration with the German chemical conglomerate [[IG Farben]], which developed methods for discharging chlorine gas against an [[trench|entrenched]] enemy.<ref>{{Cite book| url=https://books.google.com/books?id=G9FljcEASycC&pg=PA226| page=226| title=Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production| isbn=978-0-262-69313-4| author1=Smil, Vaclav| year=2000| publisher=MIT Press| url-status=live| archive-url=https://web.archive.org/web/20151231220856/https://books.google.com/books?id=G9FljcEASycC&pg=PA226| archive-date=2015-12-31}}</ref> After its first use, both sides in the conflict used chlorine as a chemical weapon, but it was soon replaced by the more deadly [[phosgene]] and [[mustard gas]].<ref name="First World War">{{cite web|url=http://www.firstworldwar.com/weaponry/gas.htm|title=Weapons of War: Poison Gas|publisher=First World War.com|access-date=2007-08-12|url-status=live|archive-url=https://web.archive.org/web/20070821004525/http://www.firstworldwar.com/weaponry/gas.htm|archive-date=2007-08-21}}</ref>

==== Middle east ====
{{Main|Chlorine bombings in Iraq|Use of chemical weapons in the Syrian Civil War}}

Chlorine gas was also used during the [[Iraq War in Anbar Province]] in 2007, with insurgents packing [[truck bomb]]s with [[mortar (weapon)|mortar]] shells and chlorine tanks. The attacks killed two people from the explosives and sickened more than 350. Most of the deaths were caused by the force of the explosions rather than the effects of chlorine since the toxic gas is readily dispersed and diluted in the atmosphere by the blast. In some bombings, over a hundred civilians were hospitalized due to breathing difficulties. The Iraqi authorities tightened security for elemental chlorine, which is essential for providing safe drinking water to the population.<ref name="cnnchlorine">{{cite news|url=http://www.cnn.com/2007/WORLD/meast/03/17/iraq.main/index.html|last=Mahdi|first=Basim|publisher=CNN|date=2007-03-17|access-date=2007-03-17|title=Iraq gas attack makes hundreds ill|url-status=live|archive-url=https://web.archive.org/web/20070317201051/http://www.cnn.com/2007/WORLD/meast/03/17/iraq.main/index.html|archive-date=2007-03-17}}</ref><ref name="Chlorine bomb BBC">{{cite news|url = http://news.bbc.co.uk/2/hi/middle_east/6660585.stm|work = BBC News|date = 2007-05-17|access-date = 2007-05-17|title = 'Chlorine bomb' hits Iraq village|url-status = dead|archive-url = https://web.archive.org/web/20070526010713/http://news.bbc.co.uk/2/hi/middle_east/6660585.stm|archive-date = 2007-05-26}}</ref>

On 23 October 2014, it was reported that the [[Islamic State of Iraq and the Levant]] had used chlorine gas in the town of Duluiyah, [[Iraq]].<ref>{{cite news|url=https://www.washingtonpost.com/world/middle_east/islamic-state-militants-allegedly-used-chlorine-gas-against-iraqi-security-forces/2014/10/23/c865c943-1c93-4ac0-a7ed-033218f15cbb_story.html|title=Islamic State militants allegedly used chlorine gas against Iraqi security forces|newspaper=[[The Washington Post]]|first=Loveday|last=Morris|date=2014-10-23|access-date=2021-06-08|archive-date=2021-12-19|archive-url=https://web.archive.org/web/20211219012039/https://www.washingtonpost.com/world/middle_east/islamic-state-militants-allegedly-used-chlorine-gas-against-iraqi-security-forces/2014/10/23/c865c943-1c93-4ac0-a7ed-033218f15cbb_story.html|url-status=live}}</ref> Laboratory analysis of clothing and soil samples confirmed the use of chlorine gas against Kurdish [[Peshmerga]] Forces in a vehicle-borne improvised explosive device attack on 23 January 2015 at the Highway 47 Kiske Junction near Mosul.<ref>{{cite news|url=https://www.dropbox.com/s/efilp3g8mxwiev4/Lab-Report-Kisic-Junction-Chlorine.pdf?dl=0|title=Lab report on chlorine gas usage|publisher=Kurdistan Region Security Council|date=March 14, 2015|access-date=March 24, 2015|archive-date=December 30, 2023|archive-url=https://web.archive.org/web/20231230134053/https://www.dropbox.com/s/efilp3g8mxwiev4/Lab-Report-Kisic-Junction-Chlorine.pdf?dl=0|url-status=live}}</ref>

Another country in the middle east, [[Syria]], has used chlorine as a [[chemical weapon]]<ref>{{cite news |url=https://www.nytimes.com/2017/02/13/world/middleeast/syrian-chlorine-bombs-aleppo-human-rights-watch.html?_r=0 |title=Syria Used Chlorine Bombs Systematically in Aleppo, Report Says |access-date=2017-05-10 |url-status=live |archive-url=https://web.archive.org/web/20170515042507/https://www.nytimes.com/2017/02/13/world/middleeast/syrian-chlorine-bombs-aleppo-human-rights-watch.html?_r=0 |archive-date=2017-05-15 |newspaper=The New York Times |date=2017-02-13 |last1=Gladstone |first1=Rick }}</ref> delivered from [[barrel bomb]]s and rockets.<ref>{{cite news |url=https://www.bbc.com/news/world-middle-east-37291182 |title=Syrian forces 'drop chlorine' on Aleppo |access-date=2017-05-10 |url-status=live |archive-url=https://web.archive.org/web/20170513191745/http://www.bbc.com/news/world-middle-east-37291182 |archive-date=2017-05-13 |work=BBC News |date=2016-09-07 }}</ref><ref>{{cite web |url=https://www.foxnews.com/world/ignoring-un-russia-and-assad-continue-syrian-chemical-weapons-and-bombing-attacks-labeled-war-crimes |title=Ignoring UN, Russia and Assad continue Syrian chemical weapons and bombing attacks labeled war crimes |website=[[Fox News]] |access-date=2017-05-11 |url-status=live |archive-url=https://web.archive.org/web/20170425092749/http://www.foxnews.com/world/2017/03/06/ignoring-un-russia-and-assad-continue-syrian-chemical-weapons-and-bombing-attacks-labeled-war-crimes.html |archive-date=2017-04-25 |date=2017-03-06 }}</ref> In 2016, the [[OPCW-UN Joint Investigative Mechanism]] concluded that the Syrian government used chlorine as a chemical weapon in three separate attacks.<ref>[https://www.reuters.com/article/us-mideast-crisis-syria-opcw-timeline-idUSKBN1HG1M7 "Timeline of investigations into Syria's chemical weapons"] {{Webarchive|url=https://web.archive.org/web/20211218003739/https://www.reuters.com/article/us-mideast-crisis-syria-opcw-timeline-idUSKBN1HG1M7 |date=2021-12-18 }}. Reuters. April 9, 2018.</ref> Later investigations from the OPCW's Investigation and Identification Team concluded that the [[Syrian Air Force]] was responsible for chlorine attacks in 2017 and 2018.<ref>[https://www.bbc.com/news/world-middle-east-56721409 "Syrian air force behind 2018 chlorine attack on Saraqeb, OPCW finds"] {{Webarchive|url=https://web.archive.org/web/20211218003753/https://www.bbc.com/news/world-middle-east-56721409 |date=2021-12-18 }} BBC News. April 12, 2021.</ref>