Acetylene

  • Ethyne
  • Ethine
  • Acetylene (liquefied)
Formula
HCCH
Structure
Description
A colorless gas with a faint garlic-like odor.
Uses
Illuminant, oxyacetylene welding, cutting and soldering metals, signalling, precipitating metals, manufacture of acetaldehyde, acetic acid, fuel for motor boats.

Registry Numbers and Inventories.
CAS
74-86-2
EC (EINECS/ELINCS)
200-816-9
EC Index Number
601-015-00-0
EC Class
Heating may cause an explosion; Explosive with or without contact with air; Extremely flammable
RTECS
AO9600000
RTECS class
Human Data
UN (DOT)
1001
Merck
12,91
Beilstein/Gmelin
906677
Beilstein Reference
4-01-00-00939
Swiss Giftliste 1
G-1042
Canada DSL/NDSL
DSL
US TSCA
Listed
Austrailia AICS
Listed
New Zealand
Listed
Japan ENCS (MITI)
Listed
Korea ECL
Listed

Properties.
Formula
C2H2
Formula mass
26.04
Melting point, °C
-81
Boiling point, °C
-75
Vapor pressure, mmHg
69700 (25 C)
Odor Threshold Odor threshold 620 ug/L
Critical temperature
35.2
Critical pressure
60.59
Density
0.618 g/cm3 (-55 C)
Solubility in water
16.6 g/L (20 C)
Surface tension
14.31 g/s2 (-56 C)
Refractive index
1.00087 (0 C)
Dipole moment
0 D
Dielectric constant
1 (15 C)
Partition coefficient, pKow
0.37
Heat of vaporization
21.2 kJ/mol
Heat of combustion
-1301 kJ/mol

Hazards and Protection.
Storage
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.
A B1 F
Handling
All chemicals should be considered hazardous. Avoid direct physical contact. Use appropriate, approved safety equipment. Untrained individuals should not handle this chemical or its container. Handling should occur in a chemical fume hood.
Protection
Wear appropriate protective gloves, clothing and goggles. Always wear thermal protective clothing when handling refrigerated/cryogenic liquids.
Respirators
Respiratory protective equipment is not normally required but self-contained type should be available for emergency and rescue use.
Small spills/leaks
Make no contact with the spilled material. ELIMINATE all ignition sources, combustibles and ground all equipment. Stop leak if you can do it without risk. Do not direct water at spill or source of leak. If possible, turn leaking containers so that gas escapes rather than liquid. Isolate area until gas has dispersed.
Stability
High in closed containers. Highly reactive; all mixtures of C2H2 (water saturated) in air can be exploded at pressures above 2 atmospheres.
Incompatibilities
Reacts with alkali metals, forming Hydrogen gas Can react explosively with bromine Reacts with silver, copper and lead to form sensitive, explosive salts.
Decomposition
The gas mixes well with air, explosive mixtures are easily formed. The substance may polymerize due to heating. Decomposes on heating and increasing pressure , causing fire and explosion hazard.

Fire.
Flash Point,°C
-118
Autoignition, °C
305
Upper exp. limit, %
80
Lower exp. limit, %
2.5
Fire fighting
Extinguish fire with flooding quantities of water or use dry chemical or carbon dioxide.
Fire potential
EXTREMELY FLAMMABLE. Will be easily ignited by heat, sparks or flames. Will form explosive mixtures with air. May ignite spontaneously in air.
Hazards
Vapors from liquefied gas are initially heavier than air and spread along ground. Vapors may travel to source of ignition and flash back. Containers may explode when heated.
Combustion products
Fire may produce irritating and/or toxic gases.
Health
0
 
Flammability
4
 
 
Reactivity
3
 

Health.
Exposure limit(s)
NIOSH REL: C 2500 ppm (2662 mg/m3)
Poison_Class
-
Exposure effects
Rapid breathing and rapid heart rate are common. In severe cases abnormally low blood pressure, apnea, and cardiac arrest develop. Various disturbances including headache, dizziness, mood disturbances, numbness of the extremities, sleepiness, mental confusion, poor judgement and coordination, and memory loss may occur. Prolonged or severe hypoxia results in unconsciousness. Prolonged asphyxia may produce CNS injury. Hemiparesis has been reported with volatile substance abuse. Cerebral edema with brainstem herniation may occur. Seizures have been reported following intentional inhalation.
   Ingestion
Not expected to be a route of entry.
   Inhalation
Hyperventilation may develop. Vapors may cause dizziness or asphyxiation without warning. May be toxic if inhaled at high concentrations.
   Skin
Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
   Eyes
Decreases in night vision, visual acuity, and visual fields (tunnel vision) may occur. Frothy mucous may be seen.

First aid
 
   Ingestion
Seek medical assistance.
   Inhalation
Administer 100% humidified supplemental oxygen with assisted ventilation as required. If hypoxia has been severe or prolonged, carefully evaluate for neurologic sequelae and provide supportive treatment as indicated.
   Skin
Rewarming and a variety of topical treatments are indicated for frostbite injury. See main section for more information.
   Eyes
Irrigate exposed eyes with copious amounts of tepid water for at least 15 minutes. If irritation, pain, swelling, lacrimation, or photophobia persist, the patient should be seen in a health care facility.

Transport.
UN number
1001
Response guide
Hazard class
2.1
USCG CHRIS Code
ACE
 
Std. Transport #
4905701