Substance profile
Methyl Isocyanate
Methyl Isocyanate is a colorless liquid with a sharp, unpleasant odor.
01 · Identification
What Methyl Isocyanate is
Methyl Isocyanate is a colorless liquid with a sharp, unpleasant odor. Its molecular formula is C2H3NO and its molecular weight is 57.05 g/mol. It boils at 39.5 °C, melts at -45 °C.
Under the GHS it carries the signal word Danger. It is classed as hazardous Air Pollutants (HAPs).
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 |
|---|---|
| H225 | Highly flammable liquid and vapour. |
| H361d | Suspected of damaging the unborn child. |
| H330 | Fatal if inhaled. |
| H311 | Toxic in contact with skin. |
| H301 | Toxic if swallowed. |
| H335 | May cause respiratory irritation. |
| H315 | Causes skin irritation. |
| H318 | Causes serious eye damage. |
| H334 | May cause allergy or asthma symptoms or breathing difficulties if inhaled. |
| H317 | May cause an allergic skin reaction. |
Precautionary statements: P210, P233, P241, P242, P260, P261, P264, P270, P271, P272, P280, P301, P302, P304, P305, P310, P313, P330, P332, P333, P338, P352, P403
03 · Physical and chemical properties
Methyl Isocyanate 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 | 39.5 °C (103.1 °F) | HSDB | |
| 38.89 °C (102 °F) | at 760 mmHg | CAMEO | |
| 39 °C (102.2 °F) | ICSC | ||
| Melting point | -45 °C (-49 °F) | HSDB | |
| -80 °C (-112 °F) | CAMEO | ||
| Density | 0.96 g/cm³ | NIOSH | |
| 0.9599 g/cm³ | at 20 °C | CAMEO | |
| 0.923 g/cm³ | at 27 °C | HSDB | |
| Solubility | Solubility in water at 20 °C: reaction | at 20 °C | ICSC |
| 10 G/100 ML WATER AT 15 °C | at 15 °C | HSDB | |
| Decomposes (NTP, 1992) | decomposes | CAMEO | |
| Vapor pressure | 348 mmHg | NIOSH | |
| 348 mmHg | at 20 °C | HSDB | |
| Flash point | -7.22 °C (19 °F) | HSDB | |
| Autoignition temperature | 534.44 °C (994 °F) | HSDB | |
| 535 °C (995 °F) | CAMEO | ||
| Lower explosive limit (LEL) | 5.3 % by volume | HSDB | |
| Upper explosive limit (UEL) | 26 % by volume | HSDB | |
| Vapor density | 1.42 (air = 1) | HSDB | |
| 2 (air = 1) | ICSC | ||
| About twice as heavy as air (EPA, 1998) (Relative to Air) | CAMEO | ||
| Odor threshold | The odor warning when the exposure limit value is exceeded is insufficient. | HSDB | |
| Air: 2.1 uL/L; odor safety class E. E= less than 10% of attentive persons can detect the TLV. | HSDB | ||
| Odor Threshold Low: 2.1 [ppm] | Haz-Map |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
04 · Source notes
Further notes on Methyl Isocyanate
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
Corrosivity
Methyl isocyanate diffuses through polyethylene and attacks most elastomers (fluorocarbon resins are resistant). It is dangerous to use materials other than stainless steel, nickel, or glass/ceramic in contact with methyl isocyanate. In particular, do not use iron, steel, zinc, tin, copper, or their alloys.
Source: HSDB
05 · Handling and storage
Storing and handling Methyl Isocyanate
Storage conditions
Fireproof ... Store only if stabilized.
Source: Hazardous Substances Data Bank (HSDB)
Incompatible materials
Reacts with water, which may cause runaway reaction ...
Source: Hazardous Substances Data Bank (HSDB)
Reactivity
Airborne vapors of METHYL ISOCYANATE are explosive when exposed to heat, flame or sparks. Vapor may ignite on contact with strong oxidizing agents. Emits toxic fumes of nitriles and oxides of nitrogen when heated to decomposition [Lewis, 3rd ed., 1993, p. 860]. Caused the death of thousands in 1984 in Bhopal, India when released accidentally as a vapor following an exothermic reaction caused by contamination with water [Chem. Eng. News, 1985, 63(6), p. 27]. Reacts rapidly with acids and bases (including amines). May polymerize in contact with iron, tin, copper and certain other catalysts such as triphenylarsenic oxide, triethyl phosphine and tributyltin oxide. Polymerizes at elevated temperatures. Attacks some plastics, rubbers, and coatings [NTP].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Methyl Isocyanate in the storage compatibility matrix →