Substance profile
Methanethiol
Methanethiol is a water-white liquid when below boiling point, or colorless gas with an odor of rotten cabbage.
01 · Identification
What Methanethiol is
Methanethiol is a water-white liquid when below boiling point, or colorless gas with an odor of rotten cabbage. Its molecular formula is CH4S and its molecular weight is 48.11 g/mol. It boils at 6 °C, melts at -123 °C, is soluble in water.
Under the GHS it carries the signal word Danger. It is classed as flammable agents - 4th degree.
Other names for Methanethiol
- methyl mercaptan
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. |
| H331 | Toxic if inhaled. |
| H400 | Very toxic to aquatic life. |
| H410 | Very toxic to aquatic life with long lasting effects. |
Precautionary statements: P210, P233, P260, P271, P273, P304, P310, P391, P403, P501
03 · Physical and chemical properties
Methanethiol 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 | 5.95 °C (42.7 °F) | at 760 mmHg | HSDB |
| 6.11 °C (43 °F) | NIOSH | ||
| 5.94 °C (42.7 °F) | at 760 mmHg | CAMEO | |
| Melting point | -123 °C (-189.4 °F) | HSDB | |
| -121.11 °C (-186 °F) | NIOSH | ||
| Density | 0.9 g/cm³ | ICSC | |
| 0.8665 g/cm³ | at 20 °C | DOE PAC | |
| 0.96 g/cm³ | at 25 °C | HSDB | |
| Solubility | Soluble in alcohol and ether; slightly soluble in chloroform | HSDB | |
| Soluble in petroleum naptha | HSDB | ||
| In water, 15,400 mg/L at 25 °C | at 25 °C | HSDB | |
| Vapor pressure | 1292 mmHg | NIOSH | |
| 400 mmHg | CAMEO | ||
| 1510 mmHg | at 25 °C | HSDB | |
| Flash point | -17.78 °C (0 °F) | HSDB | |
| Lower explosive limit (LEL) | 3.9 % by volume | HSDB | |
| Upper explosive limit (UEL) | 21.8 % by volume | HSDB | |
| Vapor density | 1.66 (air = 1) | HSDB | |
| Odor threshold | 0.0021 ppm (purity not specified) | HSDB | |
| High odor threshold= 0.0820 mg/m (purity not specified) | HSDB | ||
| Odor Threshold Low: 0.0000002 [ppm] | Haz-Map | ||
| Critical temperature and pressure | 196.8 °C (386.2 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
04 · Handling and storage
Storing and handling Methanethiol
Storage conditions
Separate from oxidizing materials. Store in a cool, dry, well-ventilated location.
Source: Hazardous Substances Data Bank (HSDB)
Incompatible materials
Can react dangerously with strong oxidizing agents and mercury (II) oxide.
Source: Hazardous Substances Data Bank (HSDB)
Reactivity
METHYL MERCAPTAN is a reducing agent--can react vigorously with oxidizing agents. Dangerous fire or explosion hazard when exposed to heat, flame, sparks or strong oxidizing agents (e.g., calcium hypochlorite). When heating to decomposition emits highly toxic fumes of oxides of sulfur [Lewis, 3rd ed., 1993, p. 862]. Violent reaction with mercury(II) oxide [Klason P., Ber., 1887, 20, p. 3410].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Methanethiol in the storage compatibility matrix →