Hydrogen sulfide

H₂SMolar mass34.08 g·mol Appearance Colorless gas OdorFoul, pungent, like that of rotten eggs Density1.539 g·L (0 °C) Melting point−85.5 °C (−121.9 °F; 187.7 K) Boiling point−59.55 °C (−75.19 °F; 213.60 K)

Solubility in water

3980 mg/L (at 20 °C) Vapor pressure1740 kPa (at 21 °C) Acidity (pK_a) 7.0 Conjugate acid Sulfonium Conjugate base Bisulfide

Magnetic susceptibility (χ)

−25.5·10 cm/mol

Refractive index (n_D)

1.000644 (0 °C) Structure

Point group

C_2v

Molecular shape

Bent

Dipole moment

0.97 D Thermochemistry

Heat capacity(C)

1.003 J K g

Std molar
entropy(S₂₉₈)

206 J mol K

Std enthalpy of
formation(Δ_fH₂₉₈)

−21 kJ mol Hazards Occupational safety and health (OHS/OSH):

Main hazards

Flammable and highly toxic GHS labelling:

Pictograms

Signal word

Danger

Hazard statements

H220, H330, H400

Precautionary statements

P210, P260, P271, P273, P284, P304+P340, P310, P320, P377, P381, P391, P403, P403+P233, P405, P501NFPA 704 (fire diamond)

4

0

Flash point−82.4 °C (−116.3 °F; 190.8 K)

Autoignition
temperature

232 °C (450 °F; 505 K) Explosive limits4.3–46% Lethal dose or concentration (LD, LC):

LC₅₀ (median concentration)

713 ppm (rat, 1 hr)
673 ppm (mouse, 1 hr)
634 ppm (mouse, 1 hr)
444 ppm (rat, 4 hr)

LC_Lo (lowest published)

600 ppm (human, 30 min)
800 ppm (human, 5 min)

NIOSH (US health exposure limits):

PEL (Permissible)

C 20 ppm; 50 ppm [10-minute maximum peak]

REL (Recommended)

C 10 ppm (15 mg/m) [10-minute]

IDLH (Immediate danger)

100 ppm Related compounds

Related hydrogen chalcogenides

Related compounds

Phosphine

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

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Hydrogen sulfide (preferred IUPAC name and American English) or hydrogen sulphide (Commonwealth English) is a chemical compound with the formulaH₂S. It is a colorless, toxic, and flammable hydrogen chalcogenide gas. Trace amounts in the ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.

Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When it is inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule.

Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestion, carried out by sulfate-reducing microorganisms. It also occurs in volcanic gases, natural gas deposits, and sometimes in well-drawn water.