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Acetylene structure

Acetylene
  • CAS：74-86-2
  • MW:26.03728
  • MF：C2H2
Acetylene (100% purity) is odourless, but commercial purity has a distinctive garlic-likeodour and is very soluble in alcohol and almost miscible with ethane. Acetylene is a flammablegas and kept under pressure in gas cylinders. Under certain conditions, acetylenecan react with copper, silver, and mercury to form acetylides, compounds which can act asignition sources. Brasses containing less than 65% copper in the alloy and certain nickelalloys are suitable for acetylene. Acetylene is not compatible with strong oxidisers such aschlorine, bromine pentafluoride, oxygen, oxygen difluoride and nitrogen trifluoride, brassmetal, calcium hypochlorite, heavy metals such as copper, silver, mercury, and their salts,bromine, chlorine, iodine, fluorine, sodium hydride, caesium hydride, ozone, perchloricacid, and potassium. View more+
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1. Names and Identifiers
1.1 Name
Acetylene
1.2 Synonyms
4-01-00-00939; Acetylen; C2H2; EINECS 200-816-9; ethenylene; Ethine; Ethyne; MFCD00008567; Narcylen; Vinylene; Welding Gas;
1.3 CAS No.
74-86-2
1.4 CID
6326
1.5 EINECS
200-816-9
1.6 Molecular Formula
C2H2
1.7 Inchi
InChI=1S/C2H2/c1-2/h1-2H
1.8 InChkey
HSFWRNGVRCDJHI-UHFFFAOYSA-N
1.9 Canonical Smiles
C#C
1.10 Isomers Smiles
C#C
2. Properties
2.1 Vapour pressure
0.91 (Air = 1)
2.2 Solubility
0.106 g/100 mL
2.3 VaporDensity
0.91 (Air = 1)
2.4 Appearance
A colorless gas with a faint garlic-like odor.
2.5 Atmospheric OH Rate Constant
8.15e-13 cm3/molecule*sec
2.6 Autoignition Temperature
581 °F (USCG, 1999)
2.7 Chemical Properties
Acetylene (100% purity) is odorless but commercial purity has a distinctive garlic-likeodor. It is very soluble in alcohol and almost miscible with ethane. Acetylene is a flammablegas and kept under pressure in gas cylinders. Under certain conditions, acetylenecan react with copper, silver, and mercury to form acetylides, compounds that can act asignition sources. Brasses contain a form acetylides, compounds that can act as ignitionsources. Brasses containing less than 65% copper in the alloy and certain nickel alloys aresuitable for acetylene. Acetylene is not compatible with strong oxidizers such as chlorine,bromine pentafl uoride, oxygen, oxygen difl uoride, and nitrogen trifl uoride, brass metal,calcium hypochlorite, heavy metals such as copper, silver, mercury, and their salts, bromine,chlorine, iodine, fl uorine, sodium hydride, cesium hydride, ozone, perchloric acid,or potassium.
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2.8 Physical Properties
Acetylene, which is the simplest alkyne hydrocarbon, exists as a colorless, flammable, unstable gas with a distinctive pleasant odor (acetylene prepared from calcium carbide has a garlic smell resulting from traces of phosphine produced in this process). The term acetylenes is used generically in the petroleum industry to denote chemicals based on the carbon-carbon triple bond.
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2.9 Color/Form
Colorless gas ... [Note: Shipped under pressure dissolved in acetone].
2.10 Decomposition
/Acetylene/, the extremely endothermic gas ... may decomposed explosively in absence of air ... /and/ readily escalates to detonation in tubular vessels. This type of explosive decomposition has been experienced in a 7 mile acetylene pipeline system ... Accidental local heating to 185 °C or above of part of the wall (as little as 6 sq cm may be enough) of a cylinder containing acetylene may lead to the development of an extremely dangerous situation. At this temperature, exothermic and self-sustaining decomposition of (endothermic) acetylene may set in, and if not stopped by rapid and effective cooling (large volume water spray), the cylinder may explode without warning. Flame flash-back into a cylinder from a wrongly adjusted and/or damaged welding or cutting torch can cause the same effect ...
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2.11 Flammability and Explosibility
Acetylene is a highly flammable gas and forms explosive mixtures with air over anunusually wide range of concentrations (2 to 80%). Acetylene can polymerizeexothermically, leading to deflagration. With a very high positive free energy offormation, acetylene is thermodynamically unstable and is sensitive to shock andpressure. Its stability is enhanced by the presence of small amounts of othercompounds such as methane, and acetylene in cylinders is relatively safe to handlebecause it is dissolved in acetone. Acetylene fires can be fought with carbon dioxide,dry chemical, and halon extinguishers; firefighting is greatly facilitated by shuttingoff the gas supply.
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2.12 Heat of Combustion
313 cal
2.13 Ionization Potential
11.40 eV
2.14 Odor
Not unpleasant odor unless impure (due to phosphine)
2.15 Odor Threshold
Air: 620 ug/L; odor safety class B; B= 50-90% of distracted persons perceive warning of TLV.
2.16 pKa
25(at 25℃)
2.17 Water Solubility
0.106 g/100 mL
2.18 Spectral Properties
INDEX OF REFRACTION: 1.00051 @ 0 DEG C/D
IR: 3961 (Sadtler Research Laboratories Prism Collection)
MASS: 61312 (NIST/EPA/MSDC Mass Spectral Database, 1990 version)
2.19 Stability
High in closed containers. Highly reactive; all mixtures of C2H2 (water saturated) in air can be exploded at pressures above 2 atmospheres.
2.20 StorageTemp
Keep in a cool, dry, dark location in a tightly sealed container or cylinder. Keep away from incompatible materials, ignition sources and untrained individuals. Secure and label area. Protect containers/cylinders from physical damage.
3. Use and Manufacturing
3.1 Definition
Agaseous alkyne. Traditionally ethyne hasfound use in oxy-acetylene weldingtorches, since its combustion with oxygenproduces a flame of very high temperature.It is also important in the organic chemicalsindustry for the production ofchloroethene (vinyl chloride), which is thestarting material for the production ofpolyvinyl chloride (PVC), and for the productionof other vinyl compounds. Untilrecently, ethyne was manufactured by thesynthesis and subsequent hydrolysis of calciumdicarbide, a very expensive procedure.Modern methods increasinglyemploy the cracking of alkanes.
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3.2 Description
Acetylene (100% purity) is odorless but commercial purity has a distinctive garlic-likeodor. It is very soluble in alcohol and almost miscible with ethane. Acetylene is a flammablegas and kept under pressure in gas cylinders. Under certain conditions, acetylenecan react with copper, silver, and mercury to form acetylides, compounds that can act asignition sources. Brasses contain a form acetylides, compounds that can act as ignitionsources. Brasses containing less than 65% copper in the al
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3.3 General Description
A colorless gas with a faint garlic-like odor. Easily ignited and burns with a sooty flame. Gas is lighter than air. Flame may flash back to the source of a leak very easily. Under prolonged exposure to fire or heat the containers may rupture violently and rocket.
3.4 Polymerization
The heating of acetylene may lead to polymerization reactions which are highly exothermic.
3.5 Potential Exposure
Acetylene can be burned in air or oxygen and is used for brazing, welding, cutting, metallizing, hardening, flame scarfing; and local heating in metallurgy. The flame is also used in the glass industry. Chemically, acetylene is used in the manufacture of vinyl chloride, acrylinitrile, synthetic rubber; vinyl acetate; trichloroethylene, acrylate, butyrolactone, 1,4-butanediol, vinyl alkyl ethers, pyrrolidone, and other substances
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3.6 Shipping
UN1001 Acetylene, dissolved, Hazard Class: 2.1; Labels: 2.1-Flammable gas. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner
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3.7 Usage
Acetylene is used in oxyacetylene flame forwelding and cutting metals; as an illuminant;as a fuel; for purifying copper, silver, andother metals; and in the manufacture ofacetic acid, acetaldehyde, and acetylides. Itis formed when calcium carbide reacts withwater. It is also obtained from cracking ofpetroleum naphtha fractions.
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4. Safety and Handling
4.1 Octanol/Water Partition Coefficient
log Kow = 0.37
4.2 Fire Hazard
Behavior in Fire: May explode in fire
4.3 Other Preventative Measures
Any leakage of acetylene will constitute a fire or explosion hazard and must be controlled immediately. Due to the characteristic odor, leaking gas is relatively easy to detect; the precise location of the leak should be determined by wiping soapy water over the suspected area--naked lights should never be used.
Areas should be kept dry, well ventilated and shielded from direct sunlight; ventilation openings should never be blocked in cold weather. Smoking, naked lights and other sources of ignition must be strictly forbidden, electrical equipment and lighting and heating facilities should be explosion proof and any hand tools employed should be of the non-sparking type. Containers, pipes, valves or fittings made of copper or copper alloys (brass, bronze) should not be used. Cylinders of dissolved acetylene should be handled carefully to prevent shocks. If a gas cylinder shows signs of internal heating the valve must be closed if possible and the cylinder liberally sprinkled using a fire extinguisher. Before any repairs or adjustments are made to containers or piping which have held acetylene, they must be well purged (with nitrogen for example) and, if necessary, completely filled with water. Dissolved acetylene should not be withdrawn from the cylinder at an hourly rate greater than a value depending on the type of the cylinder and in particular its diameter. A too fast withdrawal may carry over solvent, leaving gaseous acetylene at high pressure or may cause static electricity sparks. In installations for the manufacture or use of acetylene, safety devices must be provided to reduce pressure and flashbacks and to prevent the formation of explosive mixt. Personnel should be informed about the safety rules to be followed and not depart in any way from instructions.
Work clothing that becomes wet should be immediately removed due to its flammability hazard (i.e., for liquids with a flash point
Personnel protection: Avoid breathing vapors. Keep upwind. ... Do not handle broken packages unless wearing appropriate personal protective equipment. Approach fire with caution. /Acetylene, dissolved; Acetylene, solvent free/
If material not on fire and not involved in fire: Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. Attempt to stop leak if without undue personnel hazard. Use water spray to knock-down vapors. /Acetylene, dissolved; Acetylene, solvent free/
Evacuation: ... If material leaking (not on fire) consider evacuation from downwind area based on amount of material spilled, location and weather conditions. /Acetylene, dissolved; Acetylene, solvent free/
Although the pure material is highly endothermic ... the commercial mixture with propadiene and propane (MAPP gas) is comparable with ethylene for handling requirements and potential hazard.
Care is necessary with acetylene-fed atomic absorption spectroscopy (AAS) burners to prevent air being drawn up the liquid drainage line, when explosion is likely ... It was proposed that in student laboratories, air-acetylene flame sources should be replaced by air-natural gas flames to improve safety aspects with very little fall-off in detection limits in instrumental AA metal determinations ... Fitting of acetylene sensors inside such instruments to prevent further incidents is suggested ...
NO open flames, NO sparks, and NO smoking ... Closed system, ventilation, explosion-proof electrical equipment and lighting. Prevent build-up of electrostatic charges (eg, by grounding). Use non-sparking handtools. Use flame arrester to prevent flash-back from burner to cylinder ... Ventilation, local exhaust, or breathing protection ... Do not eat, drink, or smoke during work.
Piping material for this gas must not contain over 63% of copper. Check oxygen content before entering area. After use for welding, turn valve off; regularly check tubing, etc., and test for leaks with soap and water. The technical product may contain impurities which alter the health effects ...
SRP: Local exhaust ventilation should be applied wherever there is an incidence of point source emissions or dispersion of regulated contaminants in the work area. Ventilation control of the contaminant as close to its point of generation is both the most economical and safest method to minimize personnel exposure to airborne contaminants.
SRP: Contaminated protective clothing should be segregated in such a manner so that there is no direct personal contact by personnel who handle, dispose, or clean the clothing. Quality assurance to ascertain the completeness of the cleaning procedures should be implemented before the decontaminated protective clothing is returned for reuse by the workers. Contaminated clothing should not be taken home at end of shift, but should remain at employee's place of work for cleaning.
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4.4 Cleanup Methods
Evacuate danger area! Consult an expert! Ventilation. Remove all ignition sources. (Extra personal protection: self-contained breathing apparatus).
Eliminate all ignition sources. Stop or control the leak, if this can be done without undue risk. Use water spray to cool and disperse vapors and protect personnel. /Acetylene, dissolved/
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4.5 DisposalMethods
SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.
Gas Leakage. By forced ventilation, maintain concentration of gas below the range of explosive mixture. Remove the tank or cylinder to an open area. Leave to bleed off in the atmosphere. Disposal. Fit a pipe line into a furnace or into a pit and burn with care.
Evaporation, incineration: If practical, move leaking cylinder to a safe, outside, posted disposal area for discharge. Gas can be piped to a pit (or to a furnace when possible) and burned; or it is allowed to escape into the atmosphere. When empty close valves; return cylinder to supplier informing him of the defect.
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4.6 DOT Emergency Guidelines
/GUIDE 116: GASES - FLAMMABLE (UNSTABLE)/ Fire or Explosion: EXTREMELY FLAMMABLE. Will be easily ignited by heat, sparks or flames. Will form explosive mixtures with air. ... Vapors from liquefied gas are initially heavier than air and spread along ground. Vapors may travel to source of ignition and flash back. Cylinders exposed to fire may vent and release flammable gas through pressure relief devices. Containers may explode when heated. Ruptured cylinders may rocket. /Acetylene; Acetylene, dissolved; Acetylene solvent free/
/GUIDE 116: GASES - FLAMMABLE (UNSTABLE)/ Health: Vapors may cause dizziness or asphyxiation without warning. Some may be toxic if inhaled at high concentrations. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire may produce irritating and/or toxic gases. /Acetylene; Acetylene, dissolved; Acetylene solvent free/
/GUIDE 116: GASES - FLAMMABLE (UNSTABLE)/ Public Safety: CALL Emergency Response Telephone Number ... . As an immediate precautionary measure, isolate spill or leak area for at least 100 meters (330 feet) in all directions. Keep unauthorized personnel away. Stay upwind. Many gases are heavier than air and will spread along ground and collect in low or confined areas (sewers, basements, tanks). Keep out of low areas. /Acetylene; Acetylene, dissolved; Acetylene solvent free/
/GUIDE 116: GASES - FLAMMABLE (UNSTABLE)/ Protective Clothing: Wear positive pressure self-contained breathing apparatus (SCBA). Structural firefighters' protective clothing will only provide limited protection. /Acetylene; Acetylene, dissolved; Acetylene solvent free/
/GUIDE 116: GASES - FLAMMABLE (UNSTABLE)/ Evacuation: Large spill: Consider initial downwind evacuation for at least 800 meters (1/2 mile). Fire: If tank, rail car or tank truck is involved in a fire, ISOLATE for 1600 meters (1 mile) in all directions; also, consider initial evacuation for 1600 meters (1 mile) in all directions. /Acetylene; Acetylene, dissolved; Acetylene solvent free/
/GUIDE 116: GASES - FLAMMABLE (UNSTABLE)/ Fire: DO NOT EXTINGUISH A LEAKING GAS FIRE UNLESS LEAK CAN BE STOPPED. Small fires: Dry chemical or CO2. Large fires: Water spray or fog. Move containers from fire area if you can do it without risk. Fire involving tanks: Fight fire from maximum distance or use unmanned hose holders or monitor nozzles. Cool containers with flooding quantities of water until well after fire is out. Do not direct water at source of leak or safety devices; icing may occur. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks engulfed in fire. For massive fire, use unmanned hose holders or monitor nozzles, if this is impossible, withdraw from area and let fire burn. /Acetylene; Acetylene, dissolved; Acetylene solvent free/
/GUIDE 116: GASES - FLAMMABLE (UNSTABLE)/ Spill or Leak: ELIMINATE all ignition sources (no smoking, flares, sparks or flames in immediate area). All equipment used when handling the product must be grounded. Stop leak if you can do it without risk. Do not touch or walk through spilled material. Do not direct water at spill or source of leak. Use water spray to reduce vapors or divert vapor cloud drift. Avoid allowing water runoff to contact spilled material. If possible, turn leaking containers so that gas escapes rather than liquid. Prevent entry into waterways, sewers, basements or confined areas. Isolate area until gas has dispersed. /Acetylene; Acetylene, dissolved; Acetylene solvent free/
/GUIDE 116: GASES - FLAMMABLE (UNSTABLE)/ First Aid: Move victim to fresh air. Call 911 or emergency medical service. Give artificial respiration if victim is not breathing. Administer oxygen if breathing is difficult. Remove and isolate contaminated clothing and shoes. In case of contact with liquefied gas, thaw frosted parts with lukewarm water. In case of burns, immediately cool affected skin for as long as possible with cold water. Do not remove clothing if adhering to skin. Keep victim warm and quiet. Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves. /Acetylene; Acetylene, dissolved; Acetylene solvent free/
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4.7 Fire Fighting Procedures
Stop flow of gas before extinguishing fire. Use water spray to keep fire-exposed containers cool. Approach fire from upwind to avoid hazardous vapors and toxic decomposition products. Fight fire from protected location or maximum possible distance. Use water spray, dry chemical, form, or carbon dioxide. /Acetylene, dissolved/
Stop flow of gas. ... Carbon dioxide, dry chemical and water spray are not generally recommended because the discharged gas or volatile liquid may create a more serious explosion hazard.
If material on fire or involved in fire: Do not extinguish fire unless flow can be stopped. Use water in flooding quantities as fog. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. /Acetylene, dissolved; Acetylene, solvent free/
Evacuation: If fire becomes uncontrollable or container is exposed to direct flame - consider evacuation of one-third (1/3) mile radius. ... /Acetylene, dissolved; Acetylene, solvent free/
Shut off supply; if not possible and no risk to surroundings, let the fire burn itself out; in other cases extinguish with powder, carbon dioxide.
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4.8 FirePotential
Very dangerous fire hazard when exposed to heat or flame ...
GENERATION OF ACETYLENE, COMPRESSION...& STORAGE OF CYLINDERS...ALL ENTAIL FIRE...HAZARDS...
Flammable gas ... Low ignition energy ... /Acetylene, dissolved/
... /Acetylene/ decomposes on heating and increasing pressure, causing fire and explosion hazard.
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4.9 Safety Profile
Mtldly toxic by inhalation. Human systemic effects by inhalation: headache and dyspnea. Narcotic in high concentration. In general industrial practice, acetylene does not constitute a serious toxic hazard. It is a very dangerous fire hazard when exposed to heat, flame, or oxidizers. Moderate explosion hazard when exposed to heat or flame or by spontaneous chemical reaction. At high pressures and moderate temperatures, and in the absence of air, acetylene has been known to decompose explosively. Reacts with copper to form the explosive copper acetylide. Incompatible with brass, copper salts, copper carbide, powdered Co, Hg, Hg salts, K, Ag and Ag salts, RbH, CsH, halogens, HNO3, NaH, oxidants. Acetylene + halide + UV can explode. Molten Kignites in C2H2 and then explodes. C2H2 reacts vigorously with trifluoromethyl hypo fluorite. With O2, C2H2 can detonate very powerfully. See ACETYLIDES. When ignited, it burns with an intensely hot flame; can react vigorously with oxidizing materials. When mixed with O2 in proportions of 40% or more, acetylene acts as a narcotic and has been used in anesthesia. Acetylene O2 in the air to a level that wd not support life. However, the presence of impurities in commercial acetylene may result in the production of symptoms before an asphyxiant concentration is reached. Thus: 10% in air produces a slight intoxication, 20% produces a staggering gait, 30% produces general incoordination, 33% leads to unconsciousness in 7 minutes, up to 80% produces complete anesthesia, increased blood pressure, narcosis, and stimulated respiration. symptoms, and (in hgh concentration) semi-asphyxia and brief loss of consciousness have all been reported. See ARGON for a dmussion of simple asphyxiants. To fight fire, use CO2, water spray, or dry chemical. Stop flow of gas
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4.10 Formulations/Preparations
Grade: technical, containing 98% acetylene and not more than 0.05% by volume of phosphine or hydrogen sulfide; 99.5%.
Grades of purity: Commercial grade acetylene is supplied dissolved in acetone under pressure in cylinders.
4.11 Incompatibilities
The substance may polymerize due to heating. The substance decomposes on heating and increasing pressure, causing a fire and explosion hazard. The substance is a strong reducing agent and reacts violently with oxidants and with fluorine or chlorine under influence of light, causing fire and explosion hazard. Reacts with copper, silver, and mercury or their salts, forming shock-sensitive compounds (acetylides). The content of lines carrying acetylene must not exceed 63% copper. May form explosive mixture with air. Forms shock-sensitive mixture with copper and copper salts; mercury and mercury salts; and silver and silver salts. Reacts with brass, bromine, cesium hydride, chlorine, cobalt, cuprous acetylize; fluorine, iodine, mercuric nitrate; nitric acid, potassium, rubidium hydride; trifluoromethyl hypofluorite; and sodium hydride.
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4.12 Protective Equipment and Clothing
Where conditions ... are such that ... impurities may constitute health hazard, composition of acetylene should be determined. Respiratory protective equipment is not normally required ... /but/ self-contained type should be available for emergency & rescue use.
Compressed gases may create low temperatures when they expand rapidly. Leaks and uses that allow rapid expansion may cause a frostbite hazard. Wear appropriate personal protective clothing to prevent the skin from becoming frozen.
Wear appropriate eye protection to prevent eye contact with the liquid that could result in burns or tissue damage from frostbite.
Quick drench facilities and/or eyewash fountains should be provided within the immediate work area for emergency use where there is any possibility of exposure to liquids that are extremely cold or rapidly evaporating.
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4.13 Reactivities and Incompatibilities
Mixture with air containing between 3-82% gas is explosive. Contact with /bleaching powder may lead to formation of explosive chloroacetylenes. Finely divided /cobalt/ metal decomposes and polymerizes acetylene on contact, becoming incandescent. Copper metal forms explosive compounds with acetylene. If warmed in air or oxygen, or on impact, copper acetylides may explode in subsequent contact with acetylene. Interaction with /halogens/ can be violent or explosive. Contact of acetylene with concentrated nitric acid in presence of mercury forms explosive trinitromethane or tetranitromethane if sulfuric acid is subsequently added. Mixture with /nitric oxide products/ will ignite at +30-50 deg C. Mixtures with /oxygen/ are very explosive even at very low oxygen concentrations (
Contact of acetylene with the concn /nitric/ acid in presence of mercury(II) salts forms trinitromethane, explosive above its mp, 15 deg C. Subsequent addition of sulfuric acid produces tetranitromethane, a powerful oxidant of limited stability, in high yield.
Care is necessary with acetylene-fed atomic absorption spectroscopy (AAS) burners to prevent air being drawn up the liquid drainage line, when explosion is likely. While setting up an AAS instrument for use with nitrous oxide-acetylene, an explosion occured shortly after switching from compressed air to the oxide, when the flame became unstable. This was attributed to the outdoor location of the nitrous oxide cylinder (at 5 deg C) and the expansion cooling (4 deg C) occurring in the reducing valve, combining to reduce the oxide flow to the point of flame instability and flashback. It was proposed that in student laboratories, air-acetylene flame sources should be replaced by air-natural gas flames to improve safety aspects with very little fall-off in detection limits in instrumental AA metal determinations. Three further incidents involving explosions in AAS installations are reported, one involved accidental contamination of the acetylene inlet line by liquid acetone from an overfilled acetylene cylinder. The other explosions involved leakage of acetylene gas inside the instrument cases and ignition by the electrical controls. Fitting of acetylene sensors inside such instruments to prevent further incidents is suggested. Acetylene gas leaking from a supply tube was ignited by the source flame and a minor explosion occurred, and appears to have damaged both gas supply lines, which led to a second major explosion and fire. This involved some 6 cu m of acetylene and 18 cu m of nitrous oxide, and caused severe structural damage.
A number of explosions have been experienced when using sample soln containing perchloric acid in atomic absorption spectrometers using acetylene-nitrous oxide flames ...
Silver acetylide ... will initiate explosive acetylene-containing gas mixtures ... Formation of a deposit of ... /silver acetylide/ was observed when silver-containing soln were aspirated into an acetylene-fuelled atomic absorption spectrometer ... Both /silver and copper acetylides/ retain their hazardous properties for many months, and the former is the more effective in initiating acetylene explosions.
Incompatibilities: Heat and pressure ...
Incompatible with ... brass, copper salts, copper carbide, pyroforic cobalt, mercury, mercuric salts, ... and silver salts, RbH, CsH, ... nitric acid, NaH. Acetylene + halide + UV can explode. ... Can react vigorously with oxidizing materials.
... /IT/ FORMS EXPLOSIVE MIXT WITH AIR OR OXYGEN & ... WILL REACT WITH COPPER, SILVER OR MERCURY TO PRODUCE ACETYLIDES WHICH WHEN SUBJECT TO IMPACT, FRICTION, OR RISE IN TEMP IN DRY STATE MAY DECOMPOSE VIOLENTLY; IT ... REACTS EXPLOSIVELY WITH CHLORINE & FLUORINE.
Finely divided (pyrophoric) cobalt decomposes acetylene on contact, becoming incandescent.
Zinc; oxygen & other oxidizing agents such as halogens [Note: Forms explosive acetylide compounds with copper, mercury, silver & brasses (containing more than 66% copper).]
Unstable acetylides form when acetylene is passed over copper that has been heated enough to form a tarnish of oxide coating. In the presence of wet acetylene and ammonia, copper and brasses down to 60 percent copper react readily to form explosive acetylides.
Rubber-covered electric cable, used as a makeshift handle in the effluent pit of an acetylene plant, formed copper acetylide with residual acetylene and the former detonated when disturbed and initiated explosion of the latter. All heavy metals must be rigorously excluded from locations where acetylene may be present.
In the presence of moisture, cesium hydride reacts vigorously /with acetylene/, even at -60 deg C. When dry, no reaction occurs below 42 deg C.
Readily formed from copper or its cmpd and acetylene, /dicopper(I) acetylide/ detonates on impact or heating above 100 deg C. If warmed in air or oxygen, it explodes on subsequent contact with acetylene. Explosivity of the precipitate increases with acidity of the salt soln, while the stability increases in the presence of reducing agents (formaldehyde, hydrazine, or hydroxylamine). The form with a metallic luster was the most explosive acetylide mad. Catalysts with the acetylide supported on a porous solid are fairly stable. The ignition temperature of the pure red acetylide is 260 to 270 deg C. On exposure to air or oxygen, it is converted to black copper(II) acetylide, which ignites and explodes at 100 deg C.
... Whenever a copper or copper-rich alloy is likely to come into contact with atmospheres containing (1) ammonia, water vapor and acetylene, or (2) lime-sludge, water vapor and acetylene, or a combination of these two, there is the probability of acetylide formation and danger of explosion. The action is aided by the presence of air, or air with carbon dioxide, and hindered by the presence of nitrogen. Explosive acetylides may be formed on copper or brasses containing more than 50% copper when these are exposed to acetylene atmospheres. The acetylides produced by action of acetylene on ammoniacal or alkaline solutions of copper(II) salts are more explosive than those from the corresponding copper(I) salts. The hydrated forms are less explosive than the anhydrous material ... In contact with acetylene, silver and mercury salts will also give explosive acetylides, the mercury derivatives being complex ... Formation of silver acetylide on silver-containing solders needs higher acetylene and ammonia concn than for formation of copper acetylide. Acetylides are always formed on brass and copper or on silver-containing solders in an atmosphere of acetylene derived from calcium carbide (and which contains traces of phosphine) ...
If warmed in air or oxygen for several hours, /cuprous carbide/ explodes when brought in contact with acetylene.
Acetylene forms a sensitive acetylide when passed into an aqueous solution of mercuric nitrate.
Insoluble, explosive acetylide is formed with mercury.
An Insoluble, explosive acetylide is formed with silver.
Mercury salts and silver salts give acetylides from ammoniacal solutions in the same way copper salts do. The dried acetylides are extremely sensitive and violent.
Silver acetylides is formed on precipitation of an ammoniacal solution of silver nitrate with acetylene. Silver acetylide is highly explosive in the dry state.
Ignition occurred when acetylene and potassium hydroxide came in contact. The incendivity of potassium hydroxide on acetylene and acetylene/nitrogen mixtures is reported in various temperature and pressure ranges.
If moisture is present, rubidium hydride reacts vigorously with acetylene, even at -60 deg C.
If moisture is present, the reaction between sodium hydride and acetylene is vigorous even at -60 deg C.
... Solid acetylene in admixture with liquid nitrogen at -181 deg C is sensitized by presence fo grit (carborundum) and may readily explode on impact ... Explosions in acetylene generators and distribution systems (formerly including domestic lighting installations) /have been reported/ where faulty pressure control has allowed pressures to approach 1.4 bar, when explosion occurs in presence of moisture ... Acetylene at 170 deg C is somewhat stabilized by presence of acetic acid ... The explosibility of acetylene, alone or admixed with air, hydrogen or ethylene has been reviewed, including boundary limits for deflagration/detonation transformation ...
In a plant producing 200 kt/a /kilotons per annum/ of ethylene from cracked naphtha, acetylene in the product was hydrogenated to ethylene in a catalytic unit operated under conditions mild enough not to hydrogenate ethylene. During a temporary shut-down and probably owing to operating error, the internal temperature in the catalytic unit rose to about 400 deg C, though the external wall temperature was recorded as excessive at 120 deg C. Attempts to reduce the temperature by passing in additional ethylene were unsuccessful, as the conditions were now severe enough to hydrogenate ethylene. This exothermic reaction increased the temperature, finally to 950 deg C, and the extensive cracking to methane, carbon and hydrogen now occurring was accompanied by further pressure increase. Plant failure was followed by an explosion and fire which took 4 days to extinguish, and damage totalled 6M sterling.
Addition of 0.3 to 3.5 wt% of propane or butane reduces the explosion hazards of acetylene-air mixtures. Out of 10 gaseous additives tested for effect on the threshold temperature for initiation of explosive decomposition of acetylene by a heated wire at 2 to 22 bar, nitrogen oxide, hydrogen bromide, hydrogen chloride, hydrogen iodine and vivyl bromide showed stabilizing effects, and sulfur dioxide a mild destabilizing effect ... /Gaseous additives/
Tetrabromoethane is made by passing acetylene into bromine in carbon tetrachloride at reflux. The rate of reaction falls off rapidly below reflux temperature, and if the rate of addition of acetylene is insufficient to maintain the temperature, high concn of unreacted acetylene build up, with the possibility of a violent delayed reaction. In absence of a diluent, reaction may be explosive. Mixtures of acetylene and chlorine may explode upon initiation by sunlight or other UV source, or at high temperature, sometimes very violently. Interaction with fluorine is very violent and with iodine possibly explosive. Dilution of equimolar mixtures of chlorine and acetylene with 55 mol% of nitrogen or 70% air prevented spontaneous explosion. At higher dilutions, sparking did not initiate explosion. Explosive interaction of chlorine and acetylene in the dark is initiated by presence of oxygen at between 0.1 and about 40 vol%. The reaction is inhibited by inert gases or oxygen at higher concn. Safe techniques for demonstrating explosive combination of acetylene and chlorine have been described ... involving dropping a small lump of calcium carbide into acidified sodium hypochlorite soln. Tetrachloroethane is manufactured by reacting excess chlorine with acetylene at 100 deg C in presence of ferric chloride. On one occasion the temperature fell to 60 deg C ... and there was an explosion. It was suggested that monochloroacetylene had formed and decomposed, initiating an acetylene/chlorine or gas/air explosion. A number of such explosions have occurred, particularly during start-up. Another explosion was attributed to damp ferric chloride.
Liquid nitrogen should not be used as a trap coolant with acetylene, owing to the explosive nature of liquid or solid acetylene.
Since acetylene is endothermic ... and effectively a reducing agent, its reactions with oxidants are usually violent or explosive if uncontrolled.
The explosion of acetylene-oxygen mixtures in open vessels is a very dangerous experiment (stoichiometric mixtures detonate with great violence, completely shattering the container) ... When a mixture of acetylene and oxygen (54:46) at 270 deg C/10.9 bar was compressed in 0.7 sec to 56.1 bar, the resulting explosion attained a pressure of several kbar. In other tests rapid compression of acetylene or its mixtures with air caused no explosions. Previously, passage of acetylene into liquid air to deliberately generate a paste of solid acetylene and liquid oxygen, 'by far the most powerful of explosives', had been proposed. Acetylene had been collected for teaching purposes over water in a pneumatic trough. Later, oxygen was collected in the same way without changing the water, and the sample exploded violently when exposed to a glowing splint. Acetylene remaining dissolved in the water had apparently been displaced by the oxygen stream, the lower explosive limit for acetylene being only 2.5% in air, and less in oxygen.
A combination of faulty equipment and careless working led to an extremely violent explosion during oxy-acetylene cutting work. The oxygen cylinder was nearly empty and the regulator had a cracked diaphragm. The acetylene cylinder was lying on its side and was feeding a mixture of liquid acetone and acetylene gas to the burner head. When the oxygen ran out, the excess pressure line and into the cylinder via the cracked diaphragm. The explosion destroyed the whole plant ... A safe method for demonstrating explosive combustion of acetylene-oxygen mixtures in bubbles is described
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4.14 Safety
Mildly toxic by inhalation. Human systemic effects by inhalation: headache and dyspnea. Narcotic in high concentration. In general industrial practice, acetylene does not constitute a serious toxic hazard. It is a very dangerous fire hazard when exposed to heat, flame, or oxidizers. Moderate explosion hazard when exposed to heat or flame or by spontaneous chemical reaction. At high pressures and moderate temperatures, and in the absence of air, acetylene has been known to decompose explosively. Reacts with copper to form the explosive copper acetylide. Incompatible with brass, copper salts, copper carbide, powdered Co, Hg, Hg salts, K, Ag and Ag salts, RbH, CsH, halogens, HNO3, NaH, oxidants. Acetylene + halide + UV can explode. Molten K ignites in C2H2 and then explodes. C2H2 reacts vigorously with trifluoromethyl hypofluorite. With O2, C2H2 can detonate very powerfully. See ACETYLIDES. When ignited, it burns with an intensely hot flame; can react vigorously with oxidizing materials.When mixed with O2 in proportions of 40% or more, acetylene acts as a narcotic and has been used in anesthesia. Acetylene acts as a simple asphyxiant by diluting the O2 in the air to a level that will not support life. However, the presence of impurities in commercial acetylene may result in the production of symptoms before an asphyxiant concentration is reached. Thus: 10% in air produces a slight intoxication, 20% produces a staggering gait, 30% produces general incoordination, 33% leads to unconsciousness in 7 minutes, up to 80% produces complete anesthesia, increased blood pressure, narcosis, and stimulated respiration.Dizziness, headache, mild gastric symptoms, and (in high concentration) semi-asphyxia and brief loss of consciousness have all been reported. See ARGON for a discussion of simple asphyxiants. To fight fire, use CO2, water spray, or dry chemical. Stop flow of gas.
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4.15 Specification

Safety Statements:9-16-33
9:Keep container in a well-ventilated place
16:Keep away from sources of ignition - No smoking
33:Take precautionary measures against static discharges
4.16 Toxicity
Headache, dizziness and loss of consciousness may occur. Death from ``smothering'' may occur if oxygen content of the air is severely reduced by dilution with Acetylene.
5. MSDS

2.Hazard identification

2.1 Classification of the substance or mixture

Gases under pressure: Compressed gas

Flammable gases, Category 1

2.2 GHS label elements, including precautionary statements

Pictogram(s)
Signal word

Danger

Hazard statement(s)

H220 Extremely flammable gas
Precautionary statement(s)
Prevention

P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.

Response

P377 Leaking gas fire: Do not extinguish, unless leak can be stopped safely.

P381 In case of leakage, eliminate all ignition sources.

Storage

P410+P403 Protect from sunlight. Store in a well-ventilated place.

P403 Store in a well-ventilated place.

Disposal

none

2.3 Other hazards which do not result in classification

none

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6. NMR Spectrum
ESR : PHOTOLYSIS OF HI/ACETYLENE IN ARGON MATRIX  
ESR : REACTION WITH H ATOM IN ARGON MATRIX  
ESR : UV IRRAD. IN ARGON AT 4.2K  
13C NMR : Predict  
1H NMR : Predict  
Predict 1H proton NMR  
Mass spectrum (electron ionization)  
7. Synthesis Route
74-86-2Total: 319 Synthesis Route
 
79-35-6
79-35-6 31 Suppliers
 
74-86-2
74-86-2 65 Suppliers
 
79-01-6
79-01-6 237 Suppliers
 
156-59-2
156-59-2 26 Suppliers
 
74-86-2
74-86-2 65 Suppliers
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8. Precursor and Product
precursor:
75-35-4
75-35-4
79-27-6
79-27-6
96-37-7
96-37-7
78-74-0
78-74-0
78-66-0
78-66-0
79-35-6
79-35-6
78-54-6
78-54-6
79-01-6
79-01-6
product:
75-08-1
75-08-1
86-73-7
86-73-7
75-37-6
75-37-6
79-27-6
79-27-6
95-13-6
95-13-6
79-02-7
79-02-7
78-79-5
78-79-5
74-99-7
74-99-7
75-15-0
75-15-0
75-94-5
75-94-5
9. Computed Properties
10.Other Information
Description
Acetylene (100% purity) is odourless, but commercial purity has a distinctive garlic-like odour and is very soluble in alcohol and almost miscible with ethane. Acetylene is a flammable gas and kept under pressure in gas cylinders. Under certain conditions, acetylene can react with copper, silver, and mercury to form acetylides, compounds which can act as ignition sources. Brasses containing less than 65% copper in the alloy and certain nickel alloys are suitable for acetylene. Acetylene is not compatible with strong oxidisers such as chlorine, bromine pentafluoride, oxygen, oxygen difluoride and nitrogen trifluoride, brass metal, calcium hypochlorite, heavy metals such as copper, silver, mercury, and their salts, bromine, chlorine, iodine, fluorine, sodium hydride, caesium hydride, ozone, perchloric acid, and potassium.
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Chemical Properties
Acetylene (100% purity) is odorless but commercial purity has a distinctive garlic-like odor. It is very soluble in alcohol and almost miscible with ethane. Acetylene is a flammable gas and kept under pressure in gas cylinders. Under certain conditions, acetylene can react with copper, silver, and mercury to form acetylides, compounds that can act as ignition sources. Brasses contain a form acetylides, compounds that can act as ignition sources. Brasses containing less than 65% copper in the alloy and certain nickel alloys are suitable for acetylene. Acetylene is not compatible with strong oxidizers such as chlorine, bromine pentafl uoride, oxygen, oxygen difl uoride, and nitrogen trifl uoride, brass metal, calcium hypochlorite, heavy metals such as copper, silver, mercury, and their salts, bromine, chlorine, iodine, fl uorine, sodium hydride, cesium hydride, ozone, perchloric acid, or potassium.
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Chemical Properties
Acetylene is an extremely flammable, colorless, compressed gas. It has a faint ethereal odor when pure; a garlic-like odor when contaminated
Physical properties
Acetylene, which is the simplest alkyne hydrocarbon, exists as a colorless, flammable, unstable gas with a distinctive pleasant odor (acetylene prepared from calcium carbide has a garlic smell resulting from traces of phosphine produced in this process). The term acetylenes is used generically in the petroleum industry to denote chemicals based on the carbon-carbon triple bond.
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History
Acetylene was discovered in 1836 by Edmund Davy (1785-1857) who produced the gas while trying to make potassium metal from potassium carbide (K2C2). In 1859, Marcel Morren in France produced acetylene by running an electric arc between carbon electrodes in the presence of hydrogen. Morren called the gas produced carbonized hydrogen. Three years later, Pierre Eugène-Marcelin Berthelot (1827-1907) repeated Morren’s experiment and identified carbonized hydrogen as acetylene.
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Uses
Acetylene is used in oxyacetylene flame forwelding and cutting metals; as an illuminant;as a fuel; for purifying copper, silver, andother metals; and in the manufacture ofacetic acid, acetaldehyde, and acetylides. Itis formed when calcium carbide reacts withwater. It is also obtained from cracking ofpetroleum naphtha fractions.
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Uses
About 80% of acetylene production is used as a closed-system manufacturing intermediate for the production of other chemicals. The other chemicals synthesized from acetylene include vinyl chloride monomer, N-vinylcarbazole, 1,4- butanediol, vinyl ethers, N-vinyl-2-pyrrolidone, vinyl fluoride, N-vinylcaprolactam, and vinyl esters. The other use of acetylene as oxyacetylene torches for metal cutting and welding is about 20%.
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Uses
Illuminant, oxyacetylene welding, cutting, and soldering metals, signalling; pptg metals, particularly Cu; manufacture of acetaldehyde, acetic acid; fuel for motor boats.
Definition
A gaseous alkyne. Traditionally ethyne has found use in oxy-acetylene welding torches, since its combustion with oxygen produces a flame of very high temperature. It is also important in the organic chemicals industry for the production of chloroethene (vinyl chloride), which is the starting material for the production of polyvinyl chloride (PVC), and for the production of other vinyl compounds. Until recently, ethyne was manufactured by the synthesis and subsequent hydrolysis of calcium dicarbide, a very expensive procedure. Modern methods increasingly employ the cracking of alkanes.
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Production Methods
Commercially, acetylene is produced from the pyrolysis of naphtha in a two-stage cracking process. Both acetylene and ethylene are end products. The ratio of the two products can be changed by varying the naphtha feed rate. Acetylene also has been produced by a submerged-flame process from crude oil. In essence, gasification of the crude oil occurs by means of the flame, which is supported by oxygen beneath the surface of the oil. Combustion and cracking of the oil take place at the boundaries of the flame. The composition of the cracked gas includes about 6.3% acetylene and 6.7% ethylene. Thus, further separation and purification are required. Several years ago when procedures were developed for the safe handling of acetylene on a large scale, J. W. Reppe worked out a series of reactions that later became known as “Reppe chemistry.” These reactions were particularly important to the manufacture of many high polymers and other synthetic products. Reppe and his associates were able to effect synthesis of chemicals that had been commercially unavailable. An example is the synthesis of cyclooctatetraene by heating a solution of acetylene under pressure in tetrahydrofuran in the presence of a nickel cyanide catalyst. In another reaction, acrylic acid was produced from CO and H2O in the presence of a nickel catalyst: 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.
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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)
Several processes for producing acetylene from natural gas and other petroleum products developed in the 1920s. Thermal cracking of methane involves heating methane to approximately 600℃ in an environment deficient in oxygen to prevent combustion of all the methane. Combustion of part of the methane mix increases the temperature to approximately 1,500℃, causing the remaining methane to crack according the 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.
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Reactions
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.
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General Description
A colorless gas with a faint garlic-like odor. Easily ignited and burns with a sooty flame. Gas is lighter than air. Flame may flash back to the source of a leak very easily. Under prolonged exposure to fire or heat the containers may rupture violently and rocket.
Air & Water Reactions
Highly flammable. Slightly soluble in water. Reacts with water to form toxic ammonia fumes.
Reactivity Profile
Acetylene reacts with alkali metals, forming Hydrogen gas. Acetylene can react explosively with bromine [Von Schwartz 1918. p.142 ]. Acetylene forms a sensitive acetylide when passed into an aqueous solution of mercuric nitrate, [Mellor 4:933. 1946-47]. An Acetylene torch used to drill through a plow frame, which was filled with hydrogen gas, produced an explosion [NIOSH, June 1998]. Acetylene reacts with silver, copper and lead to form sensitive, explosive salts. Since Acetylene is endothermic and effectively a reducing agent, it's reaction with oxidants can be very violent (examples: calcium hypochlorite, nitric acid, nitrogen oxide, ozone, trifluoromethyl hypofluorite, etc.). Contact of very cold liquefied gas with water may result in vigorous or violent boiling of the product and extremely rapid vaporization, due to the large temperature differences involved. If the water is hot, there is the possibility that a liquid "superheat" explosion may occur. Pressures may build to dangerous levels if liquid gas contacts water in a closed container [Handling Chemicals Safely 1980]. Acetylene and ammonia can form explosive silver salts in contact with Ag. (Renner, Hermann, Gunther Schlamp. "Silver, Silver Compounds, and Silver Alloys." Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA. 2001.).
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Hazard
The LEL of acetylene is reached well before asphyxiation can occur, and the danger of explosion is reached before any other health hazard is present. When fighting fires involving acetylene containers, the fire should be extinguished before closing the valve to the container. This is because the acetylene has such a wide flammable range that it can burn inside the container. Acetylene is incompatible with bromine, chlorine, fluorine, copper, silver, mercury, and their compounds. Acetylene has a four-digit UN identification number of 1001. The NFPA 704 designation is health 1, flammability 4, and reactivity 3. Reactivity is reduced to 2 when the acetylene is dissolved in acetone.
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Health Hazard
Headache, dizziness and loss of consciousness may occur. Death from ``smothering'' may occur if oxygen content of the air is severely reduced by dilution with Acetylene.
Health Hazard
Acetylene is an asphyxiate like other hydrocarbongases. Exposure to its atmosphere cancause death from suffocation or asphyxiationby exclusion of oxygen. It is nontoxicbut narcotic at high concentrations. An exposureto 20% concentration in air may produceheadache and dyspnea in humans; whileinhaling a 50% acetylene in air for 5 minutesmay be fatal (NIOSH 1986).
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Health Hazard
Prolonged periods of exposure to acetylene cause symptoms including headaches, respiratory diffi culty, ringing in ears, shortness of breath, wheezing, dizziness, drowsiness, unconsciousness, nausea, vomiting, and depression of all the senses. The skin of a victim of overexposure may have a blue color. Currently, there are no known adverse health effects associated with chronic exposure to the components of this compressed gas. Lack of suffi cient oxygen may cause serious injury or death. The target organs include the kidneys, CNS, liver, respiratory system, and eyes.
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Fire Hazard
Behavior in Fire: May explode in fire
Flammability and Explosibility
Acetylene is a highly flammable gas and forms explosive mixtures with air over an unusually wide range of concentrations (2 to 80%). Acetylene can polymerize exothermically, leading to deflagration. With a very high positive free energy of formation, acetylene is thermodynamically unstable and is sensitive to shock and pressure. Its stability is enhanced by the presence of small amounts of other compounds such as methane, and acetylene in cylinders is relatively safe to handle because it is dissolved in acetone. Acetylene fires can be fought with carbon dioxide, dry chemical, and halon extinguishers; firefighting is greatly facilitated by shutting off the gas supply.
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Industrial uses
Acetylene is a colorless, flammable gas with a garlic-like odor. Under compressed conditions, it is highly explosive; however, it can be safely compressed and stored in high-pressure cylinders if the cylinders are lined with absorbent material soaked with acetone. Users are cautioned not to discharge acetylene at pressures exceeding 15 psig (103 kPa), as noted by the red line on acetylene pressure gauges.
With its intense heat and controllability, the oxyacetylene flame can be used for many different welding and cutting operations including hardfacing, brazing, beveling, gouging, and scarfing. The heating capability of acetylene also can be utilized in the bending, straightening, forming, hardening, softening, and strengthening of metals.
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Safety Profile
Mtldly toxic by inhalation. Human systemic effects by inhalation: headache and dyspnea. Narcotic in high concentration. In general industrial practice, acetylene does not constitute a serious toxic hazard. It is a very dangerous fire hazard when exposed to heat, flame, or oxidizers. Moderate explosion hazard when exposed to heat or flame or by spontaneous chemical reaction. At high pressures and moderate temperatures, and in the absence of air, acetylene has been known to decompose explosively. Reacts with copper to form the explosive copper acetylide. Incompatible with brass, copper salts, copper carbide, powdered Co, Hg, Hg salts, K, Ag and Ag salts, RbH, CsH, halogens, HNO3, NaH, oxidants. Acetylene + halide + UV can explode. Molten Kignites in C2H2 and then explodes. C2H2 reacts vigorously with trifluoromethyl hypo fluorite. With O2, C2H2 can detonate very powerfully. See ACETYLIDES. When ignited, it burns with an intensely hot flame; can react vigorously with oxidizing materials. When mixed with O2 in proportions of 40% or more, acetylene acts as a narcotic and has been used in anesthesia. Acetylene O2 in the air to a level that wd not support life. However, the presence of impurities in commercial acetylene may result in the production of symptoms before an asphyxiant concentration is reached. Thus: 10% in air produces a slight intoxication, 20% produces a staggering gait, 30% produces general incoordination, 33% leads to unconsciousness in 7 minutes, up to 80% produces complete anesthesia, increased blood pressure, narcosis, and stimulated respiration. symptoms, and (in hgh concentration) semi-asphyxia and brief loss of consciousness have all been reported. See ARGON for a dmussion of simple asphyxiants. To fight fire, use CO2, water spray, or dry chemical. Stop flow of gas
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Potential Exposure
Acetylene can be burned in air or oxygen and is used for brazing, welding, cutting, metallizing, hardening, flame scarfing; and local heating in metallurgy. The flame is also used in the glass industry. Chemically, acetylene is used in the manufacture of vinyl chloride, acrylinitrile, synthetic rubber; vinyl acetate; trichloroethylene, acrylate, butyrolactone, 1,4-butanediol, vinyl alkyl ethers, pyrrolidone, and other substances
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storage
Acetylene should be kept stored in a cool, dry place in a tightly sealed container, and should only be used in a well-ventilated area. Cylinders should be separated from oxygen and other oxidizers by a minimum of 20 ft or by a barrier of non-combustible material at least 5 ft high, having a fi re resistance rating of at least 30 min. Storage in excess of 2500 cu ft is prohibited in buildings with other occupancies. Cylinders should be stored upright with a valve protection cap in place and fi rmly secured to prevent falling or being knocked over. The cylinders should be protected from physical damage and avoid dragging, rolling, sliding, or dropping the cylinder. During transport, workers should use a suitable hand truck for cylinder movement. Care should be taken to label “No Smoking” or “Open Flames” signs in the storage or use areas. There should be no sources of ignition. All electrical equipment should be explosion-proof in the storage and use areas.
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Shipping
UN1001 Acetylene, dissolved, Hazard Class: 2.1; Labels: 2.1-Flammable gas. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner
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Purification Methods
If very impure, acetylene should be purified by successive passage through spiral wash bottles containing, in this order, saturated aqueous NaHSO4, H2O, 0.2M iodine in aqueous KI (two bottles), sodium thiosulfate solution (two bottles), alkaline sodium hydrosulfite with sodium anthraquinone-2-sulfonate as indicator (two bottles), and 10% aqueous KOH solution (two bottles). The gas is then passed through a Dry-Ice trap and two drying tubes, the first containing CaCl2, and the second, Dehydrite [Mg(ClO4)2] [Conn et al. J Am Chem Soc 61 1868 1939]. Acetone vapour can be removed from acetylene by passage through H2O, then conc H2SO4, or by passage through two gas traps at -65o and -80o, conc H2SO4 and a soda lime tower, a tower of 1-mesh Al2O3 then through H2SO4 [Reichert & Nieuwland Org Synth Coll Vol I 229 1941, Wiley Org Synth Coll Vol III 853 1955, Jones & Whiting Org Synth Coll Vol IV 793 1963]. 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. [See Brandsma Preparative Acetylenic Chemistry, 1st Edn Elsevier 1971 p15, for pK, ISBN 0444409475, 2nd Edn Elsevier 1988, ISBN 0444429603, and below for sodium acetylide.] It is also available commercially as 10ppm in helium, and several concentrations in N2 for instrument calibration. [Beilstein 1 IV 939.] Sodium acetylide [1066-26-8] M 48.0, is prepared by dissolving Na (23g) in liquid NH3 (1L) and bubbling acetylene until the blue color is discharged (ca 30minutes) and evaporated to dryness [Saunders Org Synth Coll Vol III 416 1955], and is available commercially as a suspension in xylene/light mineral oil. [See entry in “Metal-organic Compounds”, Chapter 5.]
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Toxicity evaluation
Acetylene is released to the environment through various industrial waste streams of industries. Because of the vapor pressure of acetylene (4.04×104mmHg at 25°C), it exists in the environment exclusively in the form of gas. The gaseous phase of acetylene is degraded in the environment with photochemically induced hydroxyl radicals; the halflife for this photochemical degradation is approximately 20 days. The estimated Koc of acetylene is 38, and based upon this Koc value, acetylene is expected to possess high mobility if released to soil. Based on the Henry’s law constant of 0.022 atm-m3mol-1, derived from vapor pressure 4.04×104mmHg and water solubility 1200 mg l1, volatilization from moist soil is the major fate process for acetylene. In soil, biodegradation is not expected to be an important fate process for acetylene, as suggested by 0% biochemical oxygen demand (BOD) in 28 days. Acetylene is not anticipated to be adsorbed by suspended solids and sediments if released to water because of its Koc value. Removal of acetylene from water is expected to be through the volatilization process. The estimated bioconcentration factor (BCF) of 3 for acetylene suggests that the potential for bioaccumulation of acetylene in aquatic organism is low.
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Incompatibilities
The substance may polymerize due to heating. The substance decomposes on heating and increasing pressure, causing a fire and explosion hazard. The substance is a strong reducing agent and reacts violently with oxidants and with fluorine or chlorine under influence of light, causing fire and explosion hazard. Reacts with copper, silver, and mercury or their salts, forming shock-sensitive compounds (acetylides). The content of lines carrying acetylene must not exceed 63% copper. May form explosive mixture with air. Forms shock-sensitive mixture with copper and copper salts; mercury and mercury salts; and silver and silver salts. Reacts with brass, bromine, cesium hydride, chlorine, cobalt, cuprous acetylize; fluorine, iodine, mercuric nitrate; nitric acid, potassium, rubidium hydride; trifluoromethyl hypofluorite; and sodium hydride.
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Waste Disposal
Return refillable compressed gas cylinders to supplier. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations governing storage, transportation, treatment, and waste disposal. Incineration.
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12. Related Questions
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13. Realated Product Infomation
 
1. Names and Identifiers
2. Properties
3. Use and Manufacturing
4. Safety and Handling
5. Msds
6. NMR Spectrum
7. Synthesis Route
8. Precursor and Product
9. Computational chemical data
10. Other Information
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