View source for Acetylene

{{Short description|Hydrocarbon compound (HC≡CH)}}
{{Redirect|HCCH}}
{{Redirect-distinguish|Ethyne|ethane|ethene}}
{{Use dmy dates|date=October 2021}}
{{chembox
|Watchedfields  = changed
|verifiedrevid  = 477240406
|Name = Acetylene
|ImageFile = Acetylene.svg
|ImageSize = 150px
|ImageName = Acetylene
|ImageClass = skin-invert-image
|ImageFile1 = Acetylene-3D-balls.png
|ImageSize1 = 150px
|ImageName1 = Acetylene
|ImageFile2 = Acetylene-3D-vdW.png
|ImageSize2 = 150px
|ImageName2 = Acetylene – space-filling model
|ImageFile3 = Acetylene-xtal-3D-vdW-111.png
|ImageSize3 = 200px
|ImageName3 = space-filling model of solid acetylene
|PIN = Acetylene<ref name=iupac2013>{{cite book | title =  Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 375 | doi = 10.1039/9781849733069 | isbn = 978-0-85404-182-4 | quote = The name acetylene is retained for the compound HC≡CH. It is the preferred IUPAC name, but substitution of any kind is not allowed; however, in general nomenclature, substitution is allowed, for example fluoroacetylene [fluoroethyne (PIN)], but not by alkyl groups or any other group that extends the carbon chain, nor by characteristic groups expressed by suffixes. | last1 = Favre | first1 = Henri A. | last2 = Powell | first2 = Warren H. }}</ref><ref name= P-14.3.4.2 >{{cite web |url=https://iupac.qmul.ac.uk/BlueBook/P1.html#1403 |website=Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013 |location=London |publisher=Queen Mary University |title=P-14.3 Locants |author=Moss, G.P. (web version) |at=Section P-14.3.4.2&nbsp;(d) |access-date=24 August 2024}}</ref>
| SystematicName = Ethyne<ref>[http://www.acdlabs.com/iupac/nomenclature/79/r79_53.htm Acyclic Hydrocarbons. Rule A-3. Unsaturated Compounds and Univalent Radicals] {{Webarchive|url=https://web.archive.org/web/20001010202833/http://www.acdlabs.com/iupac/nomenclature/79/r79_53.htm |date=10 October 2000 }}, IUPAC Nomenclature of Organic Chemistry</ref>
|Section1 = {{Chembox Identifiers
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID = 6086
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = OC7TV75O83
|KEGG_Ref = {{keggcite|correct|kegg}}
|KEGG = C01548
|InChI = 1/C2H2/c1-2/h1-2H
|InChIKey = HSFWRNGVRCDJHI-UHFFFAOYAY
|ChEMBL_Ref = {{ebicite|correct|EBI}}
|ChEMBL = 116336
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/C2H2/c1-2/h1-2H
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = HSFWRNGVRCDJHI-UHFFFAOYSA-N
|CASNo = 74-86-2
|CASNo_Ref = {{cascite|correct|CAS}}
|UNNumber = [[List of UN Numbers 1001 to 1100|1001]] (dissolved)<br />[[List of UN Numbers 3101 to 3200|3138]] (in mixture with [[ethylene]] and [[propylene]])
|ChEBI_Ref = {{ebicite|correct|EBI}}
|ChEBI = 27518
|PubChem = 6326
|EC_number = 200-816-9
|RTECS = AO9600000
|Gmelin = 210
|Beilstein = 906677
|SMILES = C#C
}}
|Section2 = {{Chembox Properties
|C=2 | H=2
|Appearance = Colorless gas
|Odour = Odorless
|Density = 1.1772 g/L = 1.1772 kg/m<sup>3</sup> (0&nbsp;°C, 101.3 kPa)<ref name="GESTIS">{{GESTIS|Name=Acetylene|ZVG=13570|CAS=74-86-2}}</ref>
|SublimationConditions = −84&nbsp;°C; −119&nbsp;°F; 189 K (1 atm)
|MeltingPtC = −80.8
|MeltingPt_notes = [[Triple point]] at 1.27 atm
|Solubility = slightly soluble
|SolubleOther = slightly soluble in alcohol <br> soluble in [[acetone]], [[benzene]]
|MagSus = −20.8{{e|−6}} cm<sup>3</sup>/mol <ref name="CRC97">{{Cite book |url=https://www.worldcat.org/oclc/930681942 |title=CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data. |date=2016 |author1=William M. Haynes |author2=David R. Lide |author3=Thomas J. Bruno |isbn=978-1-4987-5428-6 |edition=2016-2017, 97th |location=Boca Raton, Florida |publisher=CRC Press |oclc=930681942 |access-date=4 May 2022 |archive-date=4 May 2022 |archive-url=https://web.archive.org/web/20220504220656/https://www.worldcat.org/title/crc-handbook-of-chemistry-and-physics-a-ready-reference-book-of-chemical-and-physical-data/oclc/930681942 |url-status=live }}</ref>
|ConjugateAcid = Ethynium
|pKa = 25<ref name="airliquide">{{cite web|url=http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=1#MajorApplications|title=Acetylene – Gas Encyclopedia Air Liquide|website=Air Liquide|access-date=2018-09-27|archive-date=4 May 2022|archive-url=https://web.archive.org/web/20220504220655/https://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=1#MajorApplications|url-status=live}}</ref>
|VaporPressure = 44.2 atm (20&nbsp;°C)<ref name=NIOSH>{{PGCH|0008}}</ref>
|ThermalConductivity = 21.4&nbsp;mW·m<sup>−1</sup>·K<sup>−1</sup> (300&nbsp;K) <ref name="CRC97"/>
}}
|Section3 = {{Chembox Structure
|MolShape = [[Linear (chemistry)|Linear]]
}}
|Section4 = {{Chembox Thermochemistry
|Thermochemistry_ref = <ref name="CRC97"/>
|HeatCapacity = 44.036&nbsp;J·mol<sup>−1</sup>·K<sup>−1</sup>
|Entropy = 200.927&nbsp;J·mol<sup>−1</sup>·K<sup>−1</sup>
|DeltaHform = 227.400&nbsp;kJ·mol<sup>−1</sup>
|DeltaGfree = 209.879&nbsp;kJ·mol<sup>−1</sup>
|DeltaHcombust = 1300&nbsp;kJ·mol<sup>−1</sup>
}}
|Section5 = {{Chembox Hazards
|NFPA-H = 1
|NFPA-F = 4
|NFPA-R = 3
|GHSPictograms = {{GHS02}}{{GHS07}}
|GHSSignalWord = Danger
|HPhrases = {{H-phrases|220|336}}
|PPhrases = {{P-phrases|202|210|261|271|304|340|312|377|381|403|233|405|501}}
|ExploLimits = 2.5–100%
|AutoignitionPtC = 300
|PEL = none<ref name=NIOSH/>
|REL = C 2500 ppm (2662 mg/m<sup>3</sup>)<ref name=NIOSH/>
|IDLH = N.D.<ref name=NIOSH/> 
}}
}}

'''Acetylene''' ([[Chemical nomenclature|systematic name]]: '''ethyne''') is a [[chemical compound]] with the formula {{chem2|C2H2}} and structure {{chem2|HC\tCH}}. It is a [[hydrocarbon]] and the simplest [[alkyne]].<ref>{{Cite book |author1=R. H. Petrucci |author2=W. S. Harwood |author3=F. G. Herring | title = General Chemistry | edition = 8th | publisher = Prentice-Hall | date = 2002 | page = 1072}}</ref> This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure form and thus is usually handled as a solution.<ref name="Ullmann">{{Ullmann|doi=10.1002/14356007.a01_097.pub3|year=2008|last1=Pässler|first1=Peter|last2=Hefner|title=Acetylene Chemistry|first2=Werner|last3=Buckl|first3=Klaus|last4=Meinass|first4=Helmut|last5=Meiswinkel|first5=Andreas|last6=Wernicke|first6=Hans-Jürgen|last7=Ebersberg|first7=Günter|last8=Müller|first8=Richard|last9=Bässler|first9=Jürgen|last10=Behringer|first10=Hartmut|last11=Mayer|first11=Dieter|isbn=978-3527306732}}</ref> Pure acetylene is odorless, but commercial grades usually have a marked odor due to impurities such as [[divinyl sulfide]] and [[phosphine]].<ref name=Ullmann/><ref name=msds>Compressed Gas Association (1995) [http://www.stoodyind.com/Safety/MSDS/Acetylene.pdf Material Safety and Data Sheet – Acetylene] {{webarchive |url=https://web.archive.org/web/20120711030340/http://www.stoodyind.com/safety/msds/Acetylene.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.stoodyind.com/safety/msds/Acetylene.pdf |archive-date=2022-10-09 |url-status=live |date=11 July 2012 }}</ref>

As an alkyne, acetylene is [[Saturated and unsaturated compounds|unsaturated]] because its two carbon atoms are [[Chemical bond|bonded]] together in a [[triple bond]]. The carbon–carbon triple bond places all four atoms in the same straight line, with CCH bond angles of 180°.<ref>Whitten K. W., Gailey K. D. and Davis R. E. ''General Chemistry'' (4th ed., Saunders College Publishing 1992), pp. 328–329, 1046. {{ISBN|0-03-072373-6}}.</ref> The triple bond in acetylene results in a high energy content that is released when acetylene is burned.<ref name="Myers" />

==Discovery==
Acetylene was discovered in 1836 by [[Edmund Davy]], who identified it as a "new carburet of hydrogen".<ref>Edmund Davy (August 1836) [https://books.google.com/books?id=grtZAAAAcAAJ&pg=RA1-PA62 "Notice of a new gaseous bicarburet of hydrogen"] {{Webarchive|url=https://web.archive.org/web/20160506050712/https://books.google.com/books?id=grtZAAAAcAAJ&pg=RA1-PA62 |date=6 May 2016}}, ''Report of the Sixth Meeting of the British Association for the Advancement of Science ...'', '''5''': 62–63.</ref><ref>{{cite book |title=Acetylene: Its Properties, Manufacture and Uses |last1=Miller |first1=S. A. |year=1965 |publisher=Academic Press Inc. |volume=1 |url=https://books.google.com/books?id=-u1GAQAAIAAJ |access-date=16 July 2021 |archive-date=15 April 2021 |archive-url=https://web.archive.org/web/20210415082551/https://books.google.com/books?id=-u1GAQAAIAAJ |url-status=live }}</ref> It was an accidental discovery while attempting to isolate [[potassium]] metal. By heating [[potassium carbonate]] with carbon at very high temperatures, he produced a residue of what is now known as [[potassium carbide]], (K<sub>2</sub>C<sub>2</sub>), which reacted with water to release the new gas.<ref name="Myers" /> It was rediscovered in 1860 by French chemist [[Marcellin Berthelot]], who coined the name ''acétylène''.<ref>Bertholet (1860) [http://gallica.bnf.fr/ark:/12148/bpt6k3007r/f817.image "''Note sur une nouvelle série de composés organiques, le quadricarbure d'hydrogène et ses dérivés''"] {{Webarchive|url=https://web.archive.org/web/20150713191835/http://gallica.bnf.fr/ark:/12148/bpt6k3007r/f817.image |date=13 July 2015 }} (Note on a new series of organic compounds, tetra-carbon hydride and its derivatives), ''Comptes rendus'', series 3, '''50''': 805–808.</ref> Berthelot's empirical formula for acetylene (C<sub>4</sub>H<sub>2</sub>), as well as the alternative name "''quadricarbure d'hydrogène''" (hydrogen quadricarbide), were incorrect because many chemists at that time used the wrong atomic mass for carbon (6 instead of 12).<ref>{{cite journal |last1=Ihde |first1=Aaron J. |title=The Karlsruhe Congress: A centennial retrospective |journal=Journal of Chemical Education |date=1961 |volume=38 |issue=2 |page=83 |doi=10.1021/ed038p83 |bibcode=1961JChEd..38...83I |url=https://pubs.acs.org/doi/abs/10.1021/ed038p83 |access-date=29 December 2021 |quote=Atomic weights of 6 and 12 were both in use for carbon. |archive-date=30 December 2021 |archive-url=https://web.archive.org/web/20211230033049/https://pubs.acs.org/doi/abs/10.1021/ed038p83 |url-status=live |url-access=subscription }}</ref> Berthelot was able to prepare this gas by passing vapours of organic compounds (methanol, ethanol, etc.) through a red hot tube and collecting the [[effluent]]. He also found that acetylene was formed by sparking electricity through mixed [[cyanogen]] and [[hydrogen]] gases. Berthelot later obtained acetylene directly by passing hydrogen between the poles of a [[arc lamp|carbon arc]].<ref>Berthelot (1862) [http://gallica.bnf.fr/ark:/12148/bpt6k30115/f640.image.langEN "''Synthèse de l'acétylène par la combinaison directe du carbone avec l'hydrogène''"] {{Webarchive|url=https://web.archive.org/web/20200814023647/https://gallica.bnf.fr/ark:/12148/bpt6k30115/f640.image.langEN |date=14 August 2020 }} (Synthesis of acetylene by the direct combination of carbon with hydrogen), ''Comptes rendus'', series 3, '''54''': 640–644.</ref><ref>[http://chestofbooks.com/crafts/metal/Welding-Cutting/Acetylene.html Acetylene] {{Webarchive|url=https://web.archive.org/web/20120128110843/http://chestofbooks.com/crafts/metal/Welding-Cutting/Acetylene.html |date=28 January 2012}}.</ref>

==Preparation==

=== Partial combustion of hydrocarbons ===
Since the 1950s, acetylene has mainly been manufactured by the partial combustion of [[methane]] in the US, much of the EU, and many other countries:<ref name="Ullmann"/><ref>{{cite journal |last1=Habil |first1=Phil |last2=Sachsse |first2=Hans |date=1954 |title=Herstellung von Acetylen durch unvollständige Verbrennung von Kohlenwasserstoffen mit Sauerstoff (Production of acetylene by incomplete combustion of hydrocarbons with oxygen) |journal=Chemie Ingenieur Technik |volume=26 |issue=5 |pages=245–253 |doi=10.1002/cite.330260502}}</ref><ref>{{cite journal |last1=Habil |first1=Phil |last2=Bartholoméa |first2=E. |date=1954 |title=Probleme großtechnischer Anlagen zur Erzeugung von Acetylen nach dem Sauerstoff-Verfahren (Problems of large-scale plants for the production of acetylene by the oxygen method) |journal=Chemie Ingenieur Technik |volume=26 |issue=5 |pages=253–258 |doi=10.1002/cite.330260503}}</ref>

: {{chem2|3 CH4 + 3 O2 -> C2H2 + CO + 5 H2O}}

It is a recovered side product in production of [[ethylene]] by [[Cracking (chemistry)|cracking]] of [[Hydrocarbon|hydrocarbons]]. Approximately 400,000 tonnes were produced by this method in 1983.<ref name="Ullmann" /> Its presence in ethylene is usually undesirable because of its explosive character and its ability to poison [[Ziegler–Natta catalyst|Ziegler–Natta catalysts]]. It is selectively hydrogenated into ethylene, usually using [[Palladium|Pd]]–[[Silver|Ag]] catalysts.<ref>[http://science.enotes.com/how-products-encyclopedia/acetylene Acetylene: How Products are Made] {{webarchive|url=https://web.archive.org/web/20070120055804/http://science.enotes.com/how-products-encyclopedia/acetylene|date=20 January 2007}}</ref>

=== Dehydrogenation of alkanes ===
The heaviest alkanes in petroleum and natural gas are cracked into lighter molecules which are dehydrogenated at high temperature:

: {{chem2|C2H6 -> C2H2 + 2 H2}}
: {{chem2|2 CH4 -> C2H2 + 3 H2}}

This last reaction is implemented in the process of anaerobic decomposition of methane by microwave plasma.<ref>{{Cite web |title=How it Works |url=https://www.transformmaterials.com/howitworks/ |access-date=2023-07-21 |website=Transform Materials |language=en-US}}</ref>

=== Carbochemical method ===
The first acetylene produced was by Edmund Davy in 1836, via potassium carbide.<ref>{{cite web |last1=Institution |first1=Smithsonian |title=Carbide Lamps |url=https://www.si.edu/spotlight/mining-lights-and-hats/carbide-lamps |website=Smithsonian Institution |language=en}}</ref> 
Acetylene was historically produced by hydrolysis (reaction with water) of calcium carbide:<ref name="Myers" />
:{{chem2|CaC2 + 2 H2O -> Ca(OH)2 + C2H2}}

This reaction was discovered by [[Friedrich Wöhler]] in 1862,<ref>Wohler (1862) [https://books.google.com/books?id=6zIzAAAAYAAJ&pg=RA1-PA220 "''Bildung des Acetylens durch Kohlenstoffcalcium''"] {{Webarchive|url=https://web.archive.org/web/20160512225014/https://books.google.com/books?id=6zIzAAAAYAAJ&pg=RA1-PA220|date=12 May 2016}} (Formation of actylene by calcium carbide), ''Annalen der Chemie und Pharmacie'', '''124''': 220.</ref> but a suitable commercial scale production method which allowed acetylene to be put into wider scale use was not found until 1892 by the Canadian inventor [[Thomas Willson]] while searching for a viable commercial production method for aluminum.<ref name="Willson">{{cite web |title=A National Historic Chemical Landmark - Discovery of the Commercial Processes For Making Calcium Carbide and Acetylene - Commemorative Booklet |url=https://www.acs.org/content/dam/acsorg/education/whatischemistry/landmarks/calciumcarbideacetylene/commericialization-of-calcium-carbide-and-acetylene-commemorative-booklet.pdf |website=American Chemical Society |publisher=ACS Office of Communications |access-date=10 October 2024 |date=1998}}</ref>

As late as the early 21st century, China, Japan, and Eastern Europe produced acetylene primarily by this method.<ref>{{cite book |doi=10.1002/0471238961.0103052007011414.a01 |chapter=Acetylene from Hydrocarbons |title=Kirk-Othmer Encyclopedia of Chemical Technology |year=2000 |last1=Gannon |first1=Richard E. |isbn=9780471484943 }}{{quotation needed|date=October 2024}}</ref>

The use of this technology has since declined worldwide with the notable exception of China, with its emphasis on coal-based chemical industry, as of 2013.  Otherwise [[Petroleum|oil]] has increasingly supplanted [[coal]] as the chief source of [[Redox|reduced]] carbon.<ref>{{cite book |doi=10.1002/14356007.a04_533.pub2 |chapter=Calcium Carbide |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2013 |last1=Holzrichter |first1=Klaus |last2=Knott |first2=Alfons |last3=Mertschenk |first3=Bernd |last4=Salzinger |first4=Josef |pages=1–14 |isbn=978-3-527-30673-2 }}</ref> 

Calcium carbide production requires high temperatures, ~2000&nbsp;°C, necessitating the use of an [[electric arc furnace]]. In the US, this process was an important part of the late-19th century revolution in chemistry enabled by the massive [[Hydroelectricity|hydroelectric power]] project at [[Niagara Falls]].<ref>{{cite journal |last=Freeman |first=Horace |year=1919 |title=Manufacture of Cyanamide |url=https://books.google.com/books?id=5SAzAQAAMAAJ&q=calcium+carbide&pg=PA232 |url-status=live |journal=The Chemical News and the Journal of Physical Science |volume=117 |page=232 |archive-url=https://web.archive.org/web/20210415083126/https://books.google.com/books?id=5SAzAQAAMAAJ&q=calcium+carbide&pg=PA232 |archive-date=15 April 2021 |access-date=2013-12-23}}</ref>

==Bonding==
[[File:Structure of acetylene with bond lengths and angles labeled.svg|thumb|left|100px|Bond lengths and angles in acetylene]]
In terms of [[valence bond theory]], in each carbon atom the 2s [[Atomic orbital|orbital]] [[Orbital hybridisation|hybridizes]] with one 2p orbital thus forming an sp hybrid. The other two 2p orbitals remain unhybridized. The two ends of the two sp hybrid [[orbital overlap]] to form a strong [[Sigma bond|σ valence bond]] between the carbons, while on each of the other two ends hydrogen atoms attach also by σ bonds. The two unchanged 2p orbitals form a pair of weaker [[pi bond|π bonds]].<ref>Organic Chemistry 7th ed. by J. McMurry, Thomson 2008</ref>

Since acetylene is a linear [[molecular symmetry|symmetrical molecule]], it possesses the D<sub>∞h</sub> [[Molecular symmetry#Point group|point group]].<ref>{{Housecroft3rd|pages=94–95}}</ref>

==Physical properties==
===Changes of state===
At atmospheric pressure, acetylene cannot exist as a liquid and does not have a melting point. The [[triple point]] on the [[phase diagram]] corresponds to the melting point (−80.8&nbsp;°C) at the minimal pressure at which liquid acetylene can exist (1.27 atm). At temperatures below the triple point, solid acetylene can change directly to the [[vapour]] (gas) by [[Sublimation (phase transition)|sublimation]]. The sublimation point at atmospheric pressure is −84.0&nbsp;°C.<ref>Handbook of Chemistry and Physics (60th ed., CRC Press 1979–80), p. C-303 in Table ''Physical Constants of Organic Compounds'' (listed as ''ethyne'').</ref>

===Other===
At room temperature, the solubility of acetylene in [[acetone]] is 27.9 g per kg. For the same amount of [[dimethylformamide]] (DMF), the solubility is 51 g. At
20.26 bar, the solubility increases to 689.0 and 628.0 g for acetone and DMF, respectively. These solvents are used in pressurized gas cylinders.<ref name=Ull/>

==Applications==
===Welding===
Approximately 20% of acetylene is supplied by the [[Industrial gas|industrial gases industry]] for [[oxyacetylene]] [[gas welding]] and [[Oxy-fuel welding and cutting|cutting]] due to the high temperature of the flame. Combustion of acetylene with oxygen produces a flame of over {{convert|3600|K|C F}}, releasing 11.8&nbsp;[[Kilojoule|kJ]]/g. Oxygen with acetylene is the hottest burning common gas mixture.<ref name=Linde2013>{{cite web |url=http://www.linde-gas.com/en/products_and_supply/gases_fuel/acetylene.html |title=Acetylene |access-date=2013-11-30 |publisher=Linde |website=Products and Supply > Fuel Gases |archive-date=12 January 2018 |archive-url=https://web.archive.org/web/20180112184128/http://www.linde-gas.com/en/products_and_supply/gases_fuel/acetylene.html |url-status=live }}</ref> Acetylene is the third-hottest natural chemical flame after [[dicyanoacetylene]]'s {{convert|5260|K|C F}} and [[cyanogen]] at {{convert|4798|K|C F}}. [[Oxy-fuel welding and cutting|Oxy-acetylene welding]] was a popular welding process in previous decades. The development and advantages of [[arc welding|arc-based welding processes]] have made oxy-fuel welding nearly extinct for many applications. Acetylene usage for welding has dropped significantly. On the other hand, oxy-acetylene welding ''equipment'' is quite versatile – not only because the torch is preferred for some sorts of iron or steel welding (as in certain artistic applications), but also because it lends itself easily to brazing, braze-welding, metal heating (for annealing or tempering, bending or forming), the loosening of corroded nuts and bolts, and other applications. [[Bell Canada]] cable-repair technicians still use portable acetylene-fuelled torch kits as a [[soldering]] tool for sealing lead sleeve splices in [[manhole]]s and in some aerial locations. Oxyacetylene welding may also be used in areas where electricity is not readily accessible. Oxyacetylene cutting is used in many metal fabrication shops. For use in welding and cutting, the working pressures must be controlled by a regulator, since above {{convert|15|psi|abbr=on}}, if subjected to a shockwave (caused, for example, by a [[flashback (welding)|flashback]]), acetylene [[decompose]]s explosively into [[hydrogen]] and [[carbon]].<ref>[http://www.esabna.com/euweb/oxy_handbook/589oxy3_3.htm ESAB Oxy-acetylene welding handbook – Acetylene properties] {{Webarchive|url=https://web.archive.org/web/20200510192947/https://www.esabna.com/euweb/oxy_handbook/589oxy3_3.htm |date=10 May 2020 }}.</ref>

[[File:Laskarbit.jpg|thumb|200px|Acetylene fuel container/burner as used on the island of [[Bali]]]]

===Chemicals===
Acetylene is useful for many processes, but few are conducted on a commercial scale.<ref name=trot>{{cite journal |doi=10.1021/cr400357r |title=Catalytic Reactions of Acetylene: A Feedstock for the Chemical Industry Revisited |date=2014 |last1=Trotuş |first1=Ioan-Teodor |last2=Zimmermann |first2=Tobias |last3=Schüth |first3=Ferdi |journal=Chemical Reviews |volume=114 |issue=3 |pages=1761–1782 |pmid=24228942 |doi-access=free }}</ref>

One of the major chemical applications is [[ethynylation]] of formaldehyde.<ref name="Ullmann" /> 
Acetylene adds to [[Aldehyde|aldehydes]] and [[Ketone|ketones]] to form α-ethynyl alcohols:
:[[File:Reppe-chemistry-endiol-V1.svg|300px]]
The reaction gives [[1,4-Butynediol|butynediol]], with [[propargyl alcohol]] as the by-product. [[Copper(I) acetylide|Copper acetylide]] is used as the catalyst.<ref>{{Citation |last1=Gräfje |first1=Heinz |title=Butanediols, Butenediol, and Butynediol |date=2000-06-15 |url=https://onlinelibrary.wiley.com/doi/10.1002/14356007.a04_455 |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |pages=a04_455 |editor-last=Wiley-VCH Verlag GmbH & Co. KGaA |place=Weinheim, Germany |publisher=Wiley-VCH Verlag GmbH & Co. KGaA |language=en |doi=10.1002/14356007.a04_455 |isbn=978-3-527-30673-2 |access-date=2022-03-03 |last2=Körnig |first2=Wolfgang |last3=Weitz |first3=Hans-Martin |last4=Reiß |first4=Wolfgang |last5=Steffan |first5=Guido |last6=Diehl |first6=Herbert |last7=Bosche |first7=Horst |last8=Schneider |first8=Kurt |last9=Kieczka |first9=Heinz |s2cid=178601434 |archive-date=19 March 2022 |archive-url=https://web.archive.org/web/20220319160632/https://onlinelibrary.wiley.com/doi/10.1002/14356007.a04_455 |url-status=live |url-access=subscription }}</ref><ref>{{Citation |last1=Falbe |first1=Jürgen |title=Alcohols, Aliphatic |date=2000-06-15 |url=https://onlinelibrary.wiley.com/doi/10.1002/14356007.a01_279 |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |pages=a01_279 |editor-last=Wiley-VCH Verlag GmbH & Co. KGaA |place=Weinheim, Germany |publisher=Wiley-VCH Verlag GmbH & Co. KGaA |language=en |doi=10.1002/14356007.a01_279 |isbn=978-3-527-30673-2 |access-date=2022-03-03 |last2=Bahrmann |first2=Helmut |last3=Lipps |first3=Wolfgang |last4=Mayer |first4=Dieter |archive-date=9 March 2022 |archive-url=https://web.archive.org/web/20220309153410/https://onlinelibrary.wiley.com/doi/10.1002/14356007.a01_279 |url-status=live|url-access=subscription }}</ref>

In addition to ethynylation, acetylene reacts with [[carbon monoxide]] to give [[acrylic acid]], or acrylic esters.  Metal catalysts are required. These derivatives form products such as [[acrylic fiber]]s, [[Acrylic glass|glass]]es, [[Acrylic paint|paint]]s, [[Acrylic resin|resin]]s, and [[Acrylate polymer|polymer]]s. Except in China, use of acetylene as a chemical feedstock has declined by 70% from 1965 to 2007 owing to cost and environmental considerations.<ref>{{cite journal|author1=Takashi Ohara|author2=Takahisa Sato|author3=Noboru Shimizu|author4=Günter Prescher|author5=Helmut Schwind|author6=Otto Weiberg|author7=Klaus Marten|author8=Helmut Greim|title=Acrylic Acid and Derivatives|journal=Ullmann's Encyclopedia of Industrial Chemistry|year=2003|page=7|doi=10.1002/14356007.a01_161.pub2|isbn=3527306730 }}</ref>  In China, acetylene is a major precursor to [[vinyl chloride]].<ref name=trot/>

===Historical uses===
Prior to the widespread use of petrochemicals, coal-derived acetylene was a building block for several industrial chemicals.  Thus acetylene can be hydrated to give [[acetaldehyde]], which in turn can be oxidized to acetic acid.  Processes leading to acrylates were also commercialized. Almost all of these processes became obsolete with the availability of petroleum-derived ethylene and propylene.<ref>{{cite journal |doi=10.1021/cr400276u |title=Production of Acetylene and Acetylene-based Chemicals from Coal |date=2014 |last1=Schobert |first1=Harold |journal=Chemical Reviews |volume=114 |issue=3 |pages=1743–1760 |pmid=24256089 }}</ref>

===Niche applications===
In 1881, the Russian chemist Mikhail Kucherov<ref>{{Cite journal|doi=10.1002/cber.188101401320|title=Ueber eine neue Methode direkter Addition von Wasser (Hydratation) an die Kohlenwasserstoffe der Acetylenreihe|year=1881|last1=Kutscheroff|first1=M.|journal=Berichte der Deutschen Chemischen Gesellschaft|volume=14|pages=1540–1542|url=https://zenodo.org/record/1425226|access-date=9 September 2019|archive-date=2 December 2020|archive-url=https://web.archive.org/web/20201202225306/https://zenodo.org/record/1425226|url-status=live}}</ref> described the [[Hydration reaction|hydration]] of acetylene to [[acetaldehyde]] using catalysts such as [[mercury(II) bromide]]. Before the advent of the [[Wacker process]], this reaction was conducted on an industrial scale.<ref>{{cite journal | title = Hydration of Acetylene: A 125th Anniversary | author1 = Dmitry A. Ponomarev | author2 = Sergey M. Shevchenko | journal = [[J. Chem. Educ.]] | volume = 84 | issue = 10 | year = 2007 | page = 1725 | url = http://jchemed.chem.wisc.edu/HS/Journal/Issues/2007/OctACS/ACSSub/p1725.pdf | doi = 10.1021/ed084p1725 | bibcode = 2007JChEd..84.1725P | access-date = 18 February 2009 | archive-date = 11 June 2011 | archive-url = https://web.archive.org/web/20110611190527/http://jchemed.chem.wisc.edu/HS/Journal/Issues/2007/OctACS/ACSSub/p1725.pdf | url-status = live }}</ref>

The [[polymerization]] of acetylene with [[Ziegler–Natta catalyst]]s produces [[polyacetylene]] films. Polyacetylene, a chain of CH centres with alternating single and double bonds, was one of the first discovered [[organic semiconductor]]s. Its reaction with [[iodine]] produces a highly electrically conducting material. Although such materials are not useful, these discoveries led to the developments of [[organic semiconductor]]s, as recognized by the [[Nobel Prize in Chemistry]] in 2000 to [[Alan J. Heeger]], [[Alan G MacDiarmid]], and [[Hideki Shirakawa]].<ref name=Ullmann/>

In the 1920s, pure acetylene was experimentally used as an [[inhalation anesthetic]].<ref>{{cite encyclopedia |year=1930 |title=Acetylene in medicine|encyclopedia=[[Encyclopaedia Britannica]] |edition=14|volume=1|page=119 |author=William Stanley Sykes |author-link=William Stanley Sykes |language=en}}</ref>

Acetylene is sometimes used for [[carburization]] (that is, hardening) of steel when the object is too large to fit into a furnace.<ref name=BOC2006>{{cite web |url=http://boc.com/products_and_services/by_product/acetylene/index.asp |title=Acetylene |publisher=BOC |website=Products and Services |archive-url=https://web.archive.org/web/20060517074022/http://boc.com/products_and_services/by_product/acetylene/index.asp |archive-date=2006-05-17 }}</ref>

Acetylene is used to volatilize carbon in [[radiocarbon dating]]. The carbonaceous material in an archeological sample is treated with [[lithium]] metal in a small specialized research furnace to form [[lithium carbide]] (also known as lithium acetylide). The carbide can then be reacted with water, as usual, to form acetylene gas to feed into a [[mass spectrometer]] to measure the isotopic ratio of carbon-14 to carbon-12.<ref>{{cite journal|last=Geyh, Mebus|title=Radiocarbon dating problems using acetylene as counting gas|journal=Radiocarbon|year=1990|volume=32|issue=3|pages=321–324|doi=10.2458/azu_js_rc.32.1278|url=https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/1278/1283|access-date=2013-12-26|archive-date=26 December 2013|archive-url=https://web.archive.org/web/20131226194553/https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/1278/1283|url-status=live|doi-access=free}}</ref>

Acetylene combustion produces a strong, bright light and the ubiquity of [[Carbide lamp|carbide lamps]] drove much acetylene commercialization in the early 20th century. Common applications included coastal [[Lighthouse|lighthouses]],<ref>{{Cite web|title=Lighthouse Lamps Through Time by Thomas Tag {{!}} US Lighthouse Society|url=http://uslhs.org/lighthouse-lamps-through-time|access-date=2017-02-24|website=uslhs.org|language=en|archive-date=25 February 2017|archive-url=https://web.archive.org/web/20170225130406/http://uslhs.org/lighthouse-lamps-through-time|url-status=live}}</ref> [[Street light|street lights]],
<ref name="Myers">{{Cite book|last=Myers|first=Richard L.|url=https://books.google.com/books?id=0AnJU-hralEC|title=The 100 Most Important Chemical Compounds: A Reference Guide|date=2007|publisher=ABC-CLIO|isbn=978-0-313-33758-1|language=en|pages=7–9|access-date=21 November 2015|archive-date=17 June 2016|archive-url=https://web.archive.org/web/20160617093705/https://books.google.com/books?id=0AnJU-hralEC|url-status=live}}</ref> and [[Headlamp|automobile]]<ref>Grainger, D., (2001). By cars' early light: A short history of the headlamp: 1900s lights bore port and starboard red and green lenses. National Post. [Toronto Edition] DT7.</ref> and [[Miner's helmet|mining]] [[Headlamp (outdoor)|headlamps]].<ref name="Thorpe-2005">{{cite book|last=Thorpe|first=Dave|title=Carbide Light: The Last Flame in American Mines|publisher=Bergamot Publishing|year=2005|isbn=978-0976090526}}</ref> In most of these applications, direct combustion is a [[fire hazard]], and so acetylene has been replaced, first by [[Incandescent light bulb|incandescent lighting]] and many years later by low-power/high-lumen LEDs. Nevertheless, acetylene lamps remain in limited use in remote or otherwise inaccessible areas and in countries with a weak or unreliable central [[Electrical grid|electric grid]].<ref name="Thorpe-2005"/>

==Natural occurrence==
The energy richness of the C≡C triple bond and the rather high solubility of acetylene in water make it a suitable substrate for bacteria, provided an adequate source is available.<ref>{{Cite journal |last=Akob |first=Denise |date=August 2018 |title=Acetylenotrophy: a hidden but ubiquitous microbial metabolism? |url=https://academic.oup.com/femsec/article/94/8/fiy103/5026170 |access-date=2022-07-28 |journal=FEMS Microbiology Ecology|volume=94 |issue=8 |doi=10.1093/femsec/fiy103 |pmid=29933435 |pmc=7190893 }}</ref> A number of bacteria living on acetylene have been identified. The [[enzyme]] [[acetylene hydratase]] catalyzes the hydration of acetylene to give [[acetaldehyde]]:<ref>{{cite book|first1=Felix|last1=ten Brink|editor=Peter M. H. Kroneck and Martha E. Sosa Torres|title=The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment|series=Metal Ions in Life Sciences|volume=14|year=2014|publisher=Springer|chapter=Chapter 2. Living on acetylene. A Primordial Energy Source|pages=15–35|doi=10.1007/978-94-017-9269-1_2|pmid=25416389|isbn=978-94-017-9268-4 }}</ref>

:{{chem2|C2H2 + H2O -> CH3CHO}}

Acetylene is a moderately common chemical in the universe, often associated with the atmospheres of [[gas giant]]s.<ref>{{cite press release|publisher=[[W. M. Keck Observatory]] |title=Precursor to Proteins and DNA found in Stellar Disk |date=20 December 2005 |url=http://www.keckobservatory.org/article.php?id=39 |url-status=dead |archive-url=https://web.archive.org/web/20070223211405/http://www.keckobservatory.org/article.php?id=39 |archive-date=2007-02-23 }}</ref> One curious discovery of acetylene is on [[Enceladus]], a moon of [[Saturn]]. Natural acetylene is believed to form from [[Catalysis|catalytic]] decomposition of long-chain hydrocarbons at temperatures of {{convert|1700|K|C F}} and above. Since such temperatures are highly unlikely on such a small distant body, this discovery is potentially suggestive of catalytic reactions within that moon, making it a promising site to search for prebiotic chemistry.<ref>{{cite web|publisher=[[The Planetary Society]] |author =Emily Lakdawalla |title=LPSC: Wednesday afternoon: Cassini at Enceladus |date=17 March 2006 |url=http://www.planetary.org/blog/article/00000498/ |url-status=dead |archive-url=https://web.archive.org/web/20120220053655/http://www.planetary.org/blog/article/00000498/ |archive-date=2012-02-20 }}</ref><ref>{{cite journal|journal=[[Nature (journal)|Nature]] | volume=445 | pages=376–377| date= 25 January 2007| doi = 10.1038/445376b| title= Planetary science: Inside Enceladus|author1=John Spencer |author2=David Grinspoon |pmid=17251967|issue=7126| bibcode=2007Natur.445..376S | s2cid=4427890 | doi-access=free}}</ref>

==Reactions==
===Vinylation reactions===
In [[vinylation]] reactions, H−X compounds add across the triple bond. [[Alcohol (chemistry)|Alcohols]] and [[phenols]] add to acetylene to give [[enol ether|vinyl ether]]s. [[Thiol|Thiols]] give vinyl thioethers. Similarly, [[vinylpyrrolidone]] and [[vinylcarbazole]] are produced industrially by vinylation of [[2-Pyrrolidone|2-pyrrolidone]] and [[carbazole]].<ref name=Ull>{{Ullmann|first1=Albrecht Ludwig|last1=Harreus|first2=R.|last2=Backes|first3=J.-O.|last3=Eichler|first4=R.|last4=Feuerhake|first5=C. |last5=Jäkel|first6=U.|last6=Mahn|first7=R.|last7=Pinkos|first8=R.|last8=Vogelsang|title=2-Pyrrolidone|year=2011|doi=10.1002/14356007.a22_457.pub2}}</ref><ref name=Ullmann/>
:[[File:Reppe-chemnistry-vinylization.png|300px]]

The hydration of acetylene is a vinylation reaction, but the resulting vinyl alcohol isomerizes to [[acetaldehyde]]. The reaction is catalyzed by [[Mercury (element)|mercury]] salts. This reaction once was the dominant technology for acetaldehyde production, but it has been displaced by the [[Wacker process]], which affords acetaldehyde by oxidation of [[ethylene]], a cheaper feedstock. A similar situation applies to the conversion of acetylene to the valuable [[vinyl chloride]] by [[hydrochlorination]] versus the [[oxychlorination]] of ethylene.

[[Vinyl acetate]] is used instead of acetylene for some vinylations, which are more accurately described as [[transvinylation]]s.<ref>{{cite book |doi=10.1002/047084289X.rv008|chapter=Vinyl Acetate |title=Encyclopedia of Reagents for Organic Synthesis |year=2001 |last1=Manchand |first1=Percy S. |isbn=0471936235 }}</ref> Higher esters of vinyl acetate have been used in the synthesis of [[vinyl formate]].

===Organometallic chemistry===
Acetylene and its derivatives (2-butyne, diphenylacetylene, etc.) form [[Transition metal alkyne complex|complexes with transition metals]]. Its bonding to the metal is somewhat similar to that of ethylene complexes. These complexes are intermediates in many catalytic reactions such as [[alkyne trimerisation]] to benzene, tetramerization to [[cyclooctatetraene]],<ref name=Ullmann/> and carbonylation to [[hydroquinone]]:<ref name=Cyclization>{{cite journal|author1=Reppe, Walter |author2=Kutepow, N |author3=Magin, A |title=Cyclization of Acetylenic Compounds|journal=Angewandte Chemie International Edition in English|year=1969|volume=8|issue=10|pages=727–733 |doi=10.1002/anie.196907271 }}</ref>
:[[File:Reppe-chemistry-benzene.png|240px]]
:[[File:Reppe-chemistry-cyclooctatetraene.png|240px]]
:{{chem2|Fe(CO)5 + 4 C2H2 + 2 H2O -> 2 C6H4(OH)2 + FeCO3}} at basic conditions (50–{{val|80|u=degC}}, 20–{{val|25|u=atm}}).

Metal [[acetylide]]s, species of the formula {{chem2|L_{''n''}M\sC2R}}, are also common. [[Copper(I) acetylide]] and [[silver acetylide]] can be formed in [[aqueous]] solutions with ease due to a favorable [[solubility equilibrium]].<ref name=Viehe />

===Acid-base reactions===
{{Main|Acetylide#Preparation}}
Acetylene has a [[Acid dissociation constant|p''K''<sub>a</sub>]] of 25. Acetylene can be [[deprotonation|deprotonated]] by a [[superbase]] to form an [[acetylide]]:<ref name=Viehe>{{cite book|last1=Viehe|first1=Heinz Günter|title=Chemistry of Acetylenes|url=https://archive.org/details/chemistryofacety0000vieh|url-access=registration|date=1969|publisher=Marcel Dekker, inc.|location=New York|pages=170–179 & 225–241|edition=1st|isbn=978-0824716752}}</ref>

:{{chem2 | HC\tCH + RM -> RH + HC\tCM }}

Various [[organometallic]]<ref name=Midland1990>{{Cite journal|last1=Midland|first1=M. M.|last2=McLoughlin|first2=J. I.|last3=Werley|first3=Ralph T. (Jr.)|date=1990|title=Preparation and Use of Lithium Acetylide: 1-Methyl-2-ethynyl-''endo''-3,3-dimethyl-2-norbornanol|journal=Organic Syntheses|volume=68|page=14|doi=10.15227/orgsyn.068.0014}}</ref> and [[Inorganic compound|inorganic]]<ref name=Coffman>{{cite journal|last1=Coffman|first1=Donald D.|title=Dimethylethhynylcarbinol|journal=Organic Syntheses|date=1940|volume=40|page=20|doi=10.15227/orgsyn.020.0040}}</ref> reagents are effective.

[[Image:BASF_Nsw.jpg|thumb|The ''new acetylene plant'' of [[BASF]], commissioned in 2020]]

===Hydrogenation===
Acetylene can be [[semihydrogenation|semihydrogenated]] to [[ethylene]], providing a feedstock for a variety of [[polyethylene]] plastics.  Halogens add to the triple bond.

==Safety and handling==
Acetylene is not especially toxic, but when generated from [[calcium carbide]], or CaC<sub>2</sub>, it can contain toxic impurities such as traces of [[phosphine]] and [[arsine]], which gives it a distinct [[garlic]]-like smell. It is also highly flammable, as are most light hydrocarbons, hence its use in welding. Its most singular hazard is associated with its intrinsic instability, especially when it is pressurized: under certain conditions acetylene can react in an [[exothermic]] addition-type reaction to form a number of products, typically [[benzene]] and/or [[vinylacetylene]], possibly in addition to [[carbon]] and [[hydrogen]].{{Citation needed|date=December 2016}} Although it is stable at normal pressures and temperatures, if it is subjected to pressures as low as 15 psig it can explode.<ref name="Myers" /> The safe limit for acetylene therefore is 101&nbsp;kPa<sub>gage</sub>, or 15&nbsp;psig.<ref>{{cite web | url = http://www.c-f-c.com/specgas_products/acetylene.htm | title = Acetylene Specification | access-date = 2012-05-02 | publisher = CFC StarTec LLC | archive-date = 11 March 2014 | archive-url = https://web.archive.org/web/20140311222208/http://www.c-f-c.com/specgas_products/acetylene.htm | url-status = live }}</ref><ref name="law">{{Cite web|url=https://law.resource.org/pub/us/cfr/ibr/003/cga.g-1.2009.pdf|title=law.resource.org CGA g-1 2009 (incorporated by reference)|access-date=2016-11-30|archive-date=10 October 2016|archive-url=https://web.archive.org/web/20161010200240/https://law.resource.org/pub/us/cfr/ibr/003/cga.g-1.2009.pdf|url-status=live}}</ref> Additionally, if acetylene is initiated by intense heat or a shockwave, it can decompose explosively if the absolute pressure of the gas exceeds about {{convert|200|kPa|psi}}. It is therefore supplied and stored dissolved in [[acetone]] or [[dimethylformamide]] (DMF),<ref name="law" /><ref name="Industrial Gases">{{cite book | last1 = Downie | first1 = N. A. | title = Industrial Gases | publisher = Blackie Academic & Professional | year = 1997 | location = London; New York | isbn = 978-0-7514-0352-7}}</ref><ref>{{cite book|first=Mikołaj|last=Korzun|title=1000 słów o materiałach wybuchowych i wybuchu|isbn=83-11-07044-X|year=1986|location=Warszawa|publisher=Wydawnictwo Ministerstwa Obrony Narodowej|oclc=69535236}}</ref> contained in a [[gas cylinder]] with [[Agamassan|a porous filling]], which renders it safe to transport and use, given proper handling. Acetylene cylinders should be used in the upright position to avoid withdrawing acetone during use.<ref name="EIGA">{{Cite web|url=http://eiga.web1.apollo-com.be/fileadmin/docs_pubs/Doc_123_13_Code_of_Practice_Acetylene.pdf|title=EIGA Code of Practice: Acetylene|access-date=2016-11-30|archive-url=https://web.archive.org/web/20161201014426/http://eiga.web1.apollo-com.be/fileadmin/docs_pubs/Doc_123_13_Code_of_Practice_Acetylene.pdf|archive-date=1 December 2016|url-status=dead}}</ref>

Information on safe storage of acetylene in upright cylinders is provided by the OSHA,<ref>{{Cite web|url=https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9748|title=OSHA 29 CFR 1910.102 Acetylene|access-date=2016-11-30|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201080130/https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9748|url-status=live}}</ref><ref name="OSHA">{{Cite web|url=https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10696|title=OSHA 29 CFR 1926.350 Gas Welding and cutting.|access-date=2016-11-30|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201012751/https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10696|url-status=live}}</ref> Compressed Gas Association,<ref name="law" /> United States Mine Safety and Health Administration (MSHA),<ref>[http://arlweb.msha.gov/alerts/hazardsofacetylene.htm Special Hazards of Acetylene] {{Webarchive|url=https://web.archive.org/web/20160324115350/http://arlweb.msha.gov/alerts/hazardsofacetylene.htm |date=24 March 2016 }} UNITED STATES DEPARTMENT OF LABOR Mine Safety and Health Administration – MSHA.</ref> EIGA,<ref name="EIGA" /> and other agencies.

[[Copper]] catalyses the decomposition of acetylene, and as a result acetylene should not be transported in copper pipes.<ref name="brown">{{cite web|url=http://www.brown.edu/Administration/EHS/lab/assets/SA-2.2003.pdf|date=2003-10-16|author=Daniel_Sarachick|title=ACETYLENE SAFETY ALERT|publisher=Office of Environmental Health & Safety (EHS)|access-date=2018-09-27|archive-date=13 July 2018|archive-url=https://web.archive.org/web/20180713033908/http://www.brown.edu/Administration/EHS/lab/assets/SA-2.2003.pdf|url-status=live}}</ref>

Cylinders should be stored in an area segregated from oxidizers to avoid exacerbated reaction in case of fire/leakage.<ref name="law" /><ref name="OSHA" /> Acetylene cylinders should not be stored in confined spaces, enclosed vehicles, garages, and buildings, to avoid unintended leakage leading to explosive atmosphere.<ref name="law" /><ref name="OSHA" /> In the US, National Electric Code (NEC) requires consideration for hazardous areas including those where acetylene may be released during accidents or leaks.<ref name="NFPA">{{Cite web|url=http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards?mode=code&code=70&tab=editions|title=NFPA free access to 2017 edition of NFPA 70 (NEC)|access-date=2016-11-30|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201075712/http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards?mode=code&code=70&tab=editions|url-status=live}}</ref> Consideration may include electrical classification and use of listed Group A electrical components in US.<ref name="NFPA" /> Further information on determining the areas requiring special consideration is in NFPA 497.<ref>{{Cite web|url=http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards?mode=code&code=497&tab=editions|title=NFPA Free Access to NFPA 497 – Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas|access-date=2016-11-30|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201015905/http://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards?mode=code&code=497&tab=editions|url-status=live}}</ref> In Europe, ATEX also requires consideration for hazardous areas where flammable gases may be released during accidents or leaks.<ref name="EIGA"/>

==References==
{{Reflist}}

==External links==
{{Wikiquote}}
{{Commons category}}
*[http://pureacetylenegenerator.com Acetylene Production Plant and Detailed Process] {{Webarchive|url=https://web.archive.org/web/20150411085620/http://www.pureacetylenegenerator.com/ |date=11 April 2015 }}
*[http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA5/MAIN/1ORGANIC/ORG07/MENU.HTM Acetylene at Chemistry Comes Alive!]
*{{Gutenberg|name=Acetylene, the Principles of Its Generation and Use|no=8144}}
*[https://www.youtube.com/watch?v=KXh7__ri1VQ Movie explaining acetylene formation from calcium carbide and the explosive limits forming fire hazards]
*[http://www.periodicvideos.com/videos/mv_calcium_carbide.htm Calcium Carbide & Acetylene] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
*[https://www.cdc.gov/niosh/npg/npgd0008.html CDC – NIOSH Pocket Guide to Chemical Hazards – Acetylene]

{{Alkynes}}
{{Molecules detected in outer space}}
{{Hydrides by group}}
{{Authority control}}

[[Category:Acetylene| ]]
[[Category:Alkynes]]
[[Category:Fuel gas]]
[[Category:Industrial gases]]
[[Category:Synthetic fuel technologies]]
[[Category:Explosive gases]]
[[Category:Welding]]