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Acetylene: Properties - Uses - Appearance - Reactions - Storage - Reactivity - Hazard - Production


Acetylene: Properties - Uses - Appearance - Reactions - Storage - Reactivity - Hazard - Production


Acetylene is odorless in its purest form, but industrial acetylene has a distinct smell that is similar to garlic. It is also quite soluble in alcohol and virtually miscible with ethane. The combustible gas acetylene is stored under pressure in gas cylinders. Acetylene can combine with copper, silver, and mercury to generate acetylides, which are substances that can serve as ignition sources.


Acetylene can be used with brasses and some nickel alloys that include less than 65% copper in the alloy. Strong oxidizers like bromine pentafluoride, oxygen, oxygen difluoride, and nitrogen trifluoride, as well as brass metal, calcium hypochlorite, heavy metals like copper, silver, and mercury, as well as their salts, as well as bromine, chlorine, iodine, fluorine, sodium hydride, calcium hydride, ozone, perchloric acid, and potassium, are incompatible with acetylene.




















·       4-(chloromethyl)tolunitrile


·       Ethine

·       Ethyne

·       Narcylen

·       Acetylen

·       C2H2

·       Vinylene

·       ethenylene

·       Welding Gas


·       Acetylene (non-chemical use)

·       Acetylene (chemical use)

·       acetylene ethyne

·       Drew Ameroid Amerox Acetylene 40 LTR

·       Dissolved acetylene

·       Acetylene (liquefied)









Molecular Formula






MDL Number






Molecular Weight



26.04 g/mol



MOL File






Melting point






Boiling point












vapor pressure



3.04 X 104 mmHg

(~40 atmospheres) at 16.8 °C



refractive index















25at 25






Odorless, although garlic-like or ''gassy" odor often detectable because of trace impurities



Water Solubility



0.106 g/100 mL






Acetylene is a compressed, colorless gas that is very combustible. When it is pure, it smells faintly ethereal; when it is tainted, it smells like garlic.



Chemical Properties

Acetylene is odorless in 100% purity, but it smells strongly like garlic in industrial purity. It is virtually miscible with ethane and extremely soluble in alcohol. The combustible gas acetylene is stored under pressure in gas cylinders. Acetylene can combine with copper, silver, and mercury to generate acetylides, which are substances that can serve as ignition sources. Acetylides, substances that can serve as ignition sources, are a component of brasses. Acetylene can be used with brasses and some nickel alloys that include less than 65% copper in the alloy.


Strong oxidizers like chlorine, bromine pentafluoride, oxygen, oxygen dichloride, and nitrogen trifluoride, brass metal, calcium hypochlorite, heavy metals like copper, silver, and mercury, and their salts, bromine, chlorine, iodine, fluorine, sodium hydride, cesium hydride, ozone, perchloric acid, or potassium are incompatible with acetylene.



General Description

an odorless gas with a hint of garlic. flammable with ease and emitting a sooty flame. Air is heavier than gas. Flame can very simply return to the leak's origin. The canisters may violently burst and shoot into the air when exposed to heat or fire for an extended period of time.



Reactivity Profile

1.      Alkali metals and ACETYLENE (74-86-2) react to produce hydrogen gas.

2.     Bromine and ACETYLENE(74-86-2) might react violently.

3.     When ACETYLENE(74-86-2) is added to an aqueous solution of mercuric nitrate, it transforms into a sensitive acetylide.

4.     An explosion was caused when a plow frame loaded with hydrogen gas was drilled through with an ACETYLENE(74-86-2) torch.

5.     Silver, copper, and lead react with acetylene (74-86-2) to generate delicate, explosive salts.

6.     The interaction between ACETYLENE(74-86-2), an endothermic substance that functions as a reducing agent, and oxidants can be quite intense (examples: calcium hypochlorite, nitric acid, nitrogen oxide, ozone, trifluoromethyl hypofluorite, etc.).

7.      Due to the significant temperature differences present, contact of very cold liquid gas with water may cause intense or violent boiling of the product and highly quick vaporization. The risk of a liquid "superheat" explosion exists if the water is warm. If liquid gas comes into contact with water in a confined container, pressures may increase to dangerous levels.

8.     When in contact with silver, the explosive silver salts ACETYLENE(74-86-2) and ammonia can produce.



Air & Water Reactions

Extremely flammable a little water soluble. creates poisonous ammonia gases when combined with water.



Health Hazard

There could be headaches, vertigo, and even unconsciousness. If the oxygen content of the air is significantly lowered by dilution with acetylene, death by "smothering" may result.


Acetylene exposure for extended periods of time can result in a variety of symptoms, including nausea, vomiting, dizziness, respiratory difficulties, ringing in the ears, shortness of breath, wheezing, dizziness, and unconsciousness. Overexposure victims' skin may appear blue in tone. Chronic exposure to the elements of this compressed gas has not been linked to any known harmful health effects. Death or major harm may result from insufficient oxygen. The kidneys, CNS, liver, respiratory system, and eyes are among the target organs.



Potential Exposure

Acetylene is used in metallurgy for brazing, welding, cutting, metallizing, hardening, flame scarfing, and local heating. It can be burnt in oxygen or air. The glass sector also makes use of the flame. Chemically, acetylene is used to produce trichloroethylene, acrylate, butyrolactone, 1,4-butanediol, vinyl alkyl ethers, pyrrolidone, synthetic rubber, vinyl chloride, acrylinitrile, and other compounds.



Fire Hazard

Behavior in Fire: May explode in fire



First aid

Get the victim outside. Dial a medical emergency line. If the victim is not breathing, perform artificial respiration. Give oxygen if breathing is difficult. Take off and keep contaminated clothing and shoes isolated. If you come into touch with liquefied gas, use warm water to thaw any areas that have frozen. Keep the victim cozy and silent. Make that the medical staff is informed about the substance(s) in question and takes the necessary safety measures.


As well as the document listed below, see the NIOSH criteria. Do not touch or wash the affected regions of frostbite; instead, seek medical assistance right away. DO NOT try to remove frozen garments from regions that have been exposed to the cold in order to avoid further tissue damage. If frostbite has not yet happened, wash the infected skin with soap and water right away.




Acetylene that has been dissolved, Hazard Class 2.1, Labeled as 2.1-Flammable gas, UN1001. Cylinders must be transported in a truck with good ventilation, securely upright. Spare the cylinder and the labels from harm. Federal legislation (49CFR) only permits the owner of the compressed gas cylinder to transfer and refill it. Refilling compressed gas cylinders without the owner's express written consent is against transportation regulations.




Heating the substance may cause it to polymerize. When heated and under pressure, the chemical decomposes, posing a risk of fire and explosion. The material is a potent reducer and under the influence of light interacts violently with oxidants, fluorine, and chlorine, creating a fire and explosion hazard. combines with copper, silver, and mercury in order to generate compounds that are sensitive to shock (acetylides).


Acetylene transport lines cannot include more than 63% copper. may combine explosively with air. creates a mixture that is shock-sensitive when copper, mercury, and their salts, as well as silver and their salts, are combined. reacts with sodium hydride, trifluoromethyl hypofluorite, brass, bromine, cesium hydride, chlorine, cobalt, and cuprous acetylize; fluorine, iodine, and mercuric nitrate; nitric acid, potassium, and rubidium hydride.



Waste Disposal

Send refilled compressed gas cylinders back to the source. Consult environmental regulatory organizations for advice on proper disposal procedures. Generators of this contaminant-containing trash (100 kg/mo) are required to abide by EPA standards controlling waste disposal, treatment, storage, and transportation. Incineration.



Physical properties

The simplest alkyne hydrocarbon, acetylene, occurs as a gas that is colorless, combustible, and unstable and has a distinct, pleasant odor (acetylene prepared from calcium carbide has a garlic smell resulting from traces of phosphine produced in this process). In the petroleum business, compounds with a triple bond of carbon are collectively referred to as "acetylenes."




Edmund Davy (1785–1857) discovered acetylene in 1836 while attempting to create potassium metal from potassium carbide (K2C2). By creating an electric arc between carbon electrodes and hydrogen in 1859, Marcel Morren in France created acetylene. Morren described the gas as hydrogen that had been carbonized. Morren's experiment was replicated three years later by Pierre Eugène-Marcelin Berthelot (1827-1907), who recognized carbonized hydrogen as acetylene.




The synthesis of other chemicals uses about 80% of the acetylene produced as a closed-system manufacturing intermediate. Vinyl chloride monomer, N-vinylcarbazole, 1,4-butanediol, vinyl ethers, N-vinyl-2-pyrrolidone, vinyl fluoride, N-vinylcaprolactam, and vinyl esters are among the additional compounds produced from acetylene. About 20% of acetylene is also used in oxyacetylene torches, which are used for welding and cutting metal.


As a fuel, illuminant, purifier of copper, silver, and other metals, and in the production of acetic acid, acetaldehyde, and acetylides, acetylene is used to weld and cut metals. When calcium carbide and water react, it is created. It can also be made by cracking fractions of petroleum naphtha.


pptg metals, particularly Cu; production of acetaldehyde and acetic acid; illumination; oxyacetylene welding, cutting, and soldering metals; fuel for motor boats.




an alkyne gas. Since ethyne burns with oxygen to produce an extremely hot flame, it has historically been used in oxy-acetylene welding torches. Additionally, it is critical to the synthesis of various vinyl compounds as well as chloroethene (vinyl chloride), the precursor to polyvinyl chloride (PVC), in the organic chemicals sector. Ethyne was previously produced by the expensive process of synthesizing calcium dicarbide and then hydrolyzing it. Alkanes are progressively cracked using modern techniques.



Production Methods

The traditional method of producing acetylene is from reacting lime, calcium oxide (CaO), with coke to produce calcium carbide (CaC2). The calcium carbide is then combined with water to produce acetylene:


2CaO(s) + 5C(s)2CaC2(g) + CO2(g)

CaC2(s) + 2H2O(l) C2H2(g) + Ca(OH)2(aq)


In the 1920s, a number of methods for generating acetylene from natural gas and other petroleum products were discovered. To prevent all of the methane from combusting, thermal cracking of methane entails heating methane to about 600°C in an oxygen-poor atmosphere. When some of the methane mixture is burned, the temperature rises to about 1,500°C, which causes the remaining methane to crack as shown by the following reaction:


 2CH4(g) C2H2(g) + 3H2(g).


In addition to methane, ethane, propane, ethylene, and other hydrocarbons can be used as feed gases to produce acetylene.


Acetylene is manufactured for use in industry by pyrolyzing naphtha during a two-stage cracking process. End products include acetylene and ethylene. The naphtha feed rate can be altered to alter the ratio of the two products. Additionally, crude oil has been used in a submerged-flame technique to create acetylene. In essence, the flame used to gasify the crude oil is sustained by oxygen found beneath the oil's surface. The borders of the flame are where the oil burns and cracks.


The broken gas contains 6.3% acetylene and 6.7% ethylene, roughly speaking. Therefore, additional separation and purification are necessary. J. W. Reppe devised a set of reactions that eventually came to be known as "Reppe chemistry" several years ago when protocols were created for the safe handling of acetylene on a wide scale. The production of numerous high polymers and other synthetic items benefited greatly from these reactions. Reppe and his colleagues were successful in synthesizing compounds that had previously been off-limits to commerce.


An illustration is the production of cyclooctatetraene by heating an acetylene solution under pressure in tetrahydrofuran in the presence of a catalyst made of nickel cyanide. In a different process, a nickel catalyst was used to create acrylic acid from CO and H2O:


C2H2 + CO + H2O CH2:CH·COOH.


These two reactions are representative of a much larger number of reactions, both those that are straight-chain only, and those involving ring closure.




Acetylene reacts:

(1) with chlorine, to form acetylene tetrachloride C2H2Cl4 or CHCl2·CHCl2 or acetylene dichloride C2H2Cl2 or CHCl:CHCl.

(2) with bromine, to form acetylene tetrabromide C2H2Br4 or CHBr2·CHBr2 or acetylene dibromide C2H2Br2 or CHBr:CHBr.

(3) with hydrogen chloride (bromide, iodide), to form ethylene monochloride CH2:CHCl (monobromide, monoiodide), and 1,1-dichloroethane, ethylidene chloride CH3·CHCl2 (dibromide, diiodide).

(4) with H2O in the presence of a catalyzer, e.g., mercuric sulfate HgO4S, to form acetaldehyde CH3·CHO.

(5) with hydrogen, in the presence of a catalyzer, e.g., finely divided nickel heated, to form ethylene C2H4 or ethane C2H6.

(6) with metals, such as copper or nickel, when moist, also lead or zinc, when moist and unpurified. Tin is not attacked. Sodium yields, upon heating, the compounds C2HNa and C2Na2.

(7) With ammoniocuprous (or silver) salt solution, to form cuprous (or silver) acetylide C2Cu2, dark red precipitate, explosive when dry, and yielding acetylene upon treatment with acid.

(8) with mercuric chloride solution, to form trichloromercuric acetaldehyde C(HgCl)3·CHO, precipitate, which yields with HCl acetaldehyde plus mercuric chloride.




Asphyxiation cannot happen until the LEL of acetylene is achieved, and the danger of explosion occurs before any other health hazard is evident. The fire should be put out before shutting the valve to the container when battling fires involving acetylene containers. It can fire inside the container since acetylene has such a broad range of flammability. Copper, silver, mercury, fluorine, chlorine, and their derivatives are all incompatible with acetylene.


The four-digit UN identification number for acetylene is 1001. Health 1, flammability 4, and reactivity 3 are the NFPA 704 designations. When the acetylene is dissolved in acetone, the reactivity is decreased to 2.



Flammability and Explosibility

Acetylene is a highly flammable gas that can combine explosively with air at concentrations ranging from 2 to 80%. Acetylene can exothermally polymerize, which can cause a deflagration. Acetylene has an extremely high positive free energy of production, making it thermodynamically unstable and susceptible to pressure and shock.


Small concentrations of other substances, such as methane, help to increase its stability, and because acetylene is dissolved in acetone, handling it in cylinders is generally considered to be safe. Extinguishers that use carbon dioxide, dry chemicals, or halon can put out acetylene fires; but, turning off the gas supply makes the process much easier.



Industrial uses

Acetylene is a gas that is colorless, combustible, and smells like garlic. It is highly explosive when compressed, but if the high-pressure cylinders are lined with absorbent material that has been soaked in acetone, it can be compressed and stored safely. The red line on acetylene pressure gauges indicates that users should not discharge acetylene at pressures higher than 15 psig (103 kPa).


The oxyacetylene flame can be used for a wide variety of welding and cutting operations, such as hardfacing, brazing, beveling, gouging, and scarfing, thanks to its extreme heat and controllability. Metals can be bent, straightened, formed, hardened, softened, and strengthened using acetylene's heating capabilities.



Purification Methods

Acetylene should be purified if it is extremely impure by passing it repeatedly through spiral wash bottles containing, in this order: saturated aqueous NaHSO4, H2O, 0.2M iodine in aqueous KI, sodium thiosulfate solution, alkaline sodium hydrosulfite with sodium anthraquinone-2-sulfonate as indicator, and 10% aqueous KOH solution (two bottles).


The gas is then routed through two drying tubes, the second of which contains Dehydrite [Mg(ClO4)2], and a Dry-Ice trap. J Am Chem Soc 61 1868 1939, Conn et al. By passing through H2O, then conc H2SO4, or by passing through two gas traps at -65o and -80o, conc H2SO4, a soda lime tower, a tower of 1-mesh Al2O3, and then through H2SO4, acetone vapour can be extracted from acetylene.


Sometimes it contains acetone and air. These can be removed by a series of bulb-to-bulb distillations, e.g. a train consisting of a conc H2SO4 trap and a cold EtOH trap (-73o), or passage through H2O and H2SO4, then over KOH and CaCl2. It is also available commercially as 10ppm in helium, and several concentrations in N2 for instrument calibration. 




Acetylene should only be used in well-ventilated areas and should be stored in a cool, dry location in a well sealed container. Cylinders should be kept at least 20 feet away from oxygen and other oxidizers, or behind a barrier made of non-combustible material that is at least 5 feet tall and has a 30 minute fire resistance rating. Storage in excess of 2500 cu ft is forbidden in buildings with other occupancies.


To prevent falling or being knocked over, cylinders should be stored upright with a valve protection cap in place and firmly fastened. It is important to preserve the cylinders from physical harm and to avoid dragging, rolling, sliding, or dropping them. For cylinder movement during shipment, employees should use an appropriate hand truck. In the storage or use areas, special attention should be paid to labeling "No Smoking" or "Open Flames" signage. There shouldn't be any ignition sources. In the storage and use areas, all electrical equipment should be explosion-proof.



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