Substance profile
Acetylene
Acetylene is a colorless gas with a not unpleasant odor unless impure (due to phosphine).
01 · Identification
What Acetylene is
Acetylene is a colorless gas with a not unpleasant odor unless impure (due to phosphine). Its molecular formula is C2H2 and its molecular weight is 26.04 g/mol. It boils at -83.9 °C, melts at -80.7 °C.
Under the GHS it carries the signal word Danger. It is classed as flammable agents - 4th degree.
Other names for Acetylene
- ethyne
- C2H2
- Ethine
- Narcylen
- Vinylene
02 · GHS classification
Hazards and label elements
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
| Code | Hazard statement |
|---|---|
| H220 | Extremely flammable gas. |
03 · Physical and chemical properties
Acetylene properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | -83.89 °C (-119 °F) | at 760 mmHg | CAMEO |
| -84 °C (-119.2 °F) | at 760 mmHg | DOE PAC | |
| -84.7 °C (-120.5 °F) | sublimes, sublimation point | HSDB | |
| Melting point | -80.7 °C (-113.3 °F) | triple point | HSDB |
| -80.7 °C (-113.3 °F) | DOE PAC | ||
| -83.89 °C (-119 °F) | sublimes | NIOSH | |
| Density | 0.377 g/cm³ | at 760 mmHg | HSDB |
| 0.909 g/cm³ | at 0 °C | DOE PAC | |
| 0.613 g/cm³ | at -80 °C | CAMEO | |
| Solubility | Soluble in water and many organic materials | HSDB | |
| Slightly soluble in ethanol, carbon disulfide; soluble in acetone, benzene, chloroform | HSDB | ||
| In water, 1200 mg/L at 25 °C | at 25 °C | HSDB | |
| Vapor pressure | 33590 mmHg | NIOSH | |
| 33450 mmHg | at 20 °C | ICSC | |
| Flash point | -18.15 °C (-0.7 °F) | HSDB | |
| -17.78 °C (0 °F) | Haz-Map | ||
| NA (Gas) | NIOSH | ||
| Autoignition temperature | 305 °C (581 °F) | HSDB | |
| Lower explosive limit (LEL) | 2.5 % by volume | HSDB | |
| Upper explosive limit (UEL) | 100 % by volume | HSDB | |
| 82 % by volume | HSDB | ||
| Vapor density | 0.91 (air = 1) | HSDB | |
| 0.907 (air = 1) | ICSC | ||
| Odor threshold | Air: 620 ug/L; odor safety class B; B= 50-90% of distracted persons perceive warning of TLV. | HSDB | |
| detection: 240 mg/cu m; 1300-2750 mg/cu m | HSDB | ||
| The odor threshold for acetylene is 657.2 mg/cu m. | HSDB | ||
| Critical temperature and pressure | 35.2 °C (95.4 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
04 · Handling and storage
Storing and handling Acetylene
Storage conditions
Keep container in a cool, well-ventilated area. Keep container tightly closed and sealed until ready for use. Avoid all possible sources of ignition (spark or flame). Segregate from oxidizing materials. Cylinders should be stored upright, with valve protection cap in place, and firmly secured to prevent falling or being knocked over. Cylinder temperatures should not exceed 52 degC (125 degF).
Source: Hazardous Substances Data Bank (HSDB)
Incompatible materials
Contact of acetylene with the concn /nitric/ acid in presence of mercury (II) salts forms trinitromethane, explosive above its mp, 15 °C. Subsequent addition of sulfuric acid produces tetranitromethane, a powerful oxidant of limited stability, in high yield.
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Acetylene in the storage compatibility matrix →
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