Mercaptans (Thiols) — properties & hazards overview
Typical LEL (air)
≈ 3–4 vol%
Odour threshold
ppt–ppb (very low)
Boiling range (C1–C4)
~ 6–100 °C
Water solubility
Low–moderate
Toxicity
resp./CNS irritation
Flammability
LEL ≈ 3–4%
Chronic risk
sensitisation possible
Environmental
odour nuisance
| Property | Value / Note |
|---|---|
| Generic formula | R–SH (aliphatic & aromatic thiols) |
| pKa (–SH) | ≈ 10–11 (weak acids; deprotonate in alkali) |
| Physical state | Volatile liquids (C1–C4) with intense, skunk‑like odour |
| Vapour pressure (20 °C) | High for C1–C3; moderate for C4+ |
| Best analytical method | GC–SCD (sulfur chemiluminescence) — highly selective for organosulfur with sub‑ppb limits and minimal cross‑interference; ideal for speciated mercaptans. |
| Typical sources | Natural gas odorants, petrochemical units, pulp & paper (TRS), anaerobic processes, refineries |
*Values are indicative; composition‑dependent. For safety/design, always verify via current SDS, standards, and local regulations.