HYDROGEN SULFIDE

Hydrogen sulfide
(Hydrosulfuric acid, sulfur hydride)
CAS 7783-06-4

H₂ S

Colorless gas
bp -61 °C, mp -83 °C
Slightly soluble in water (2.9 g/100 mL at 20 °C)

Strong rotten egg odor detectable at 0.001 to 0.1 ppm (mean = 0.0094 ppm); olfactory fatigue occurs quickly at high concentrations

1.189 (air = 1.0)

20 atm at 25 °C

< -82.4 °C

260 °C

LC₅₀ inhal (rat) 444 ppm (580 mg/m³)

LC_LO inhal (human) 800 ppm (1110 mg/m³; 5 min)

PEL (OSHA) 20 ppm (ceiling) (28 mg/m³)

TLV-TWA (ACGIH) 10 ppm (14 mg/m³)

STEL (ACGIH) 15 ppm (21 mg/m³)

Moderately toxic gas; inhalation of large concentrations can cause unconsciousness, respiratory paralysis, and death; highly flammable.

The acute toxicity of hydrogen sulfide by inhalation is moderate. A 5-min exposure to 800 ppm has resulted in death. Inhalation of 1000 to 2000 ppm may cause coma after a single breath. Exposure to lower concentrations may cause headache, dizziness, and upset stomach. Low concentrations of H₂ S (20 to 150 ppm) can cause eye irritation, which may be delayed in onset. Although the odor of hydrogen sulfide is detectable at very low concentrations, it rapidly causes olfactory fatigue at higher levels, and therefore is not considered to have adequate warning properties.

Hydrogen sulfide has not been shown to be carcinogenic or to have reproductive or developmental effects in humans.

Hydrogen sulfide is flammable in air in the range of 4.3 to 45.5% (NFPA rating = 4). Combustion products (sulfur oxides) are also toxic by inhalation. In the event of a hydrogen sulfide fire, stop the flow of gas if possible without risk of harmful exposure and let the fire burn itself out.

Hydrogen sulfide is incompatible with strong oxidizers. It will attack many metals, forming sulfides. Liquid hydrogen sulfide will attack some forms of plastics, rubber, and coatings. H₂ S reacts violently with a variety of metal oxides, including the oxides of chromium, mercury, silver, lead, nickel, and iron.

Because of its toxic, flammable, and gaseous nature, hydrogen sulfide should be handled using the "basic prudent practices" of Chapter 5.C, supplemented by the additional precautions for work with flammable compounds (Chapter 5.F) and for work at high pressure (Chapter 5.H). In particular, cylinders of hydrogen sulfide should be stored and used in a continuously ventilated gas cabinet or fume hood. Local fire codes should be reviewed for limitations on quantity and storage requirements.

In the event of a release of hydrogen sulfide, the area should be evacuated immediately. Use appropriate respiratory protection to rescue an affected individual. Remove exposed individual to an uncontaminated area, and seek immediate emergency help. Keep victim warm, quiet, and at rest; provide assisted respiration if breathing has stopped.

In the event of skin contact, immediately wash with soap and water and remove contaminated clothing. In case of eye contact, promptly wash with copious amounts of water for 15 min (lifting upper and lower lids occasionally) and obtain medical attention.

To respond to a release, use appropriate protective equipment and clothing. Positive pressure air-supplied respiratory protection is required. Close cylinder valve and ventilate area. Remove cylinder to a fume hood or remote area if it cannot be shut off.

Excess hydrogen sulfide should be returned to the manufacturer, according to your institution's waste disposal guidelines.

The information in this LCSS has been compiled by a committee of the National Research Council from literature sources and Material Safety Data Sheets and is believed to be accurate as of July 1994. This summary is intended for use by trained laboratory personnel in conjunction with the NRC report Prudent Practices in the Laboratory: Handling and Disposal of Chemicals. This LCSS presents a concise summary of safety information that should be adequate for most laboratory uses of the title substance, but in some cases it may be advisable to consult more comprehensive references. This information should not be used as a guide to the nonlaboratory use of this chemical.

Copyright 1995 National Academy of Sciences. All rights reserved.