Methyl mercaptan (methanethiol) — properties & hazards overview
Boiling point
5.9 °C
Flash point
−18 °C (gas at ambient)
Explosion limits (air)
3.9 – 21.8 vol%
Odour threshold
≈ 1 ppb
Toxicity
Acute inhalation hazard
Flammability
FP −18 °C; 3.9–21.8%
Chronic risk
CNS / respiratory
Environmental
Severe odour nuisance
| Property | Value / Note |
|---|---|
| Chemical formula | CH₃SH |
| Molar mass | 48.11 g/mol |
| Physical state | Gas at ambient temperature; heavier than air |
| Water solubility | ≈ 15 g/L (20 °C); pKa ≈ 10.3, so absorption improves sharply above pH 10. |
| Odour | Rotten cabbage / decayed garlic; perceptible at parts per billion. |
| Typical sources | Rendering, slaughterhouse and offal processing, kraft pulping, syngas and biogas, wastewater sludge. |
| Best analytical detection | GC with sulphur-selective detection (SCD or FPD) for speciation at ppb level; PID for continuous trending; dynamic olfactometry (EN 13725) where the permit is written in odour units. |
*Values are indicative and may vary by source. For safety and design, always consult current SDS and regulations.