Hydrogen sulfide

 

Hydrogen sulfide

Chemical formula	H2S
OTP appearance	colorless gas
Molar Mass(g/mol)	34.1
Density(g/cc)	0.001363
Melting Point(°C)	-82
Boiling Point(°C)	-60
Fuel Value(MJ/kg)	17.65
Immediate Danger to Life and Health	100ppm
NFPA 704	4 4 0

Hydrogen sulfide is a toxic gas evolved from and involved with a variety of processes. Heavier than air.

Uses

Primary

• used to precipitate certain metal ions (Pb,Cu,Hg,As) in solution:

Secondary

• Source of sulfur via the Clause Process:

2 H₂S + 3 O₂ → 2 SO₂ + 2 H₂O

4 H₂S + 2 SO₂ → 3 S₂ + 4 H₂O

Natural occurrence

• as a naturally occuring metabolic signaller in human beings
• as a byproduct of anaerobic decomposition of sulfur-containing bio-waste

Hazards

• Toxicity alarm at 10ppm, toxic at 300-350ppm
• Explosive in air at 4.3-46%, autoignition 232°C

Synthesis

• directly from sulfur and hydrogen at 450°C

  S₈(l) + 8 H₂(g) → 8 H₂S(g)

• from combining sulfuric acid and iron sulfide

  H₂SO₄(l) + FeS(s) → FeSO₄(s) + H₂S(g)

• from water on barium sulfide or aluminum sulfide.

  BaS + H₂O → BaO + H₂S

Testing

Detection

• Paper soaked in lead acetate turns dark when exposed to hydrogen sulfide when lead sulfide is formed

  (CH₃COO)₂Pb(s) + H₂S(g) → 2 CH₃COOH + 2 PbS(s)

Disposal

• Hydrogen sulfide passed over wet hematite or ground iron oxides produces iron (II,III) sulfide and water, with the oxygen in the iron oxide being displaced by sulfur.

  Fe₃O₄ + 4 H₂S → Fe₃S₄ + 4 H₂O

See Also

• Barium
• Manganese