Chemical Properties
colourless gas with strong odour of rotten eggs (odour threshold ca 0.2 ppt)
Definition
ChEBI: A sulfur hydride consisting of s single sulfur atom bonded to two hydrogen atoms. A highly poisonous, flammable gas with a characteristic odour of rotten eggs, it is often produced by bacterial decomposition of organic matter in the absence of oxygen.
Uses
To produce elemental sulfur and sulfuric acid; in manufacture of heavy water and other chemicals; in metallurgy; as analytical reagent.
Reactivity Profile
HYDROGEN SULFIDE reacts as an acid and as a reducing agent. Explodes on contact with oxygen difluoride, bromine pentafluoride, chlorine trifluoride, dichlorine oxide, silver fulminate. May ignite and explode when exposed to powdered copper in oxygen [Mertz, V. et al., Ber., 1880, 13, p. 722]. May react similarly with other powdered metals. Ignites on contact with metal oxides and peroxides (barium peroxide, chromium trioxide, copper oxide, lead dioxide, manganese dioxide, nickel oxide, silver oxide, silver dioxide, thallium trioxide, sodium peroxide, mercury oxide, calcium oxide) [Mellor, 1947, vol. 10, p. 129, 141]. Ignites with silver bromate, lead(II) hypochlorite, copper chromate, nitric acid, lead(IV) oxide and rust. May ignite if passed through rusty iron pipes [Mee, A. J., School Sci. Rev., 1940, 22(85), p. 95]. Reacts exothermically with bases. The heat of the reaction with soda lime, sodium hydroxide, potassium hydroxide, barium hydroxide may lead to ignition or explosion of the unreacted portion in the presence of air/oxygen [Mellor, 1947, vol. 10, p. 140].
Air & Water Reactions
Highly flammable; a flame can very easily flash back to the source of leak. Soluble in water to a maximum of 0.4% by mass at room temperature .
Hazard
Highly flammable, dangerous fire risk,
explosive limits in air 4.3–46%. Toxic by inhalation,
strong irritant to eyes and mucous membranes.
Health Hazard
Exposure to very high concentrations causes immediate death. Also death or permanent injury may occur after very short exposure to small quantities. It acts directly upon the nervous system resulting in paralysis of respiratory centers.
Fire Hazard
Compound is heavier than air and may travel a considerable distance to source of ignition and flash back. HYDROGEN SULFIDE forms explosive mixtures with air over a wide range. Also reacts explosively with bromine pentafluoride, chlorine trifluoride, nitrogen triiodide, nitrogen trichloride, oxygen difluoride, and phenyl diazonium chloride. When heated to decomposition, HYDROGEN SULFIDE emits highly toxic fumes of oxides of sulfur. Incompatible with many materials including strong oxidizers, metals, strong nitric acid, bromine pentafluoride, chlorine trifluoride, nitrogen triiodide, nitrogen trichloride, oxygen difluoride and phenyl diazonium chloride. Avoid physical damage to containers; sources of ignition; storage near nitric acid, strong oxidizing materials, and corrosive liquids or gases.
Description
Hydrogen Sulfide is a colorless, very poisonous, flammable gas with the
characteristic foul odor of rotten eggs. It often results
from the bacterial breakdown of organic matter in the
absence of oxygen, such as in swamps and sewers where
anaerobic digestion can take place. It also occurs in
volcanic gases, “natural gas”, and some well waters.
Hydrogen sulfide has numerous names, some of which
are archaic.
Small amounts of hydrogen sulfide occur in crude oil,
but natural gas can contain up to 90%. About 10% of the
total global emission of H2S is due to human activity.
Physical properties
H2S is soluble in
carbon disulfide, methanol, acetone and alkanolamines. A solution of hydrogen sulfide in water is initially
clear but over time turns cloudy. This is due to the
slow reaction of hydrogen sulfide with the oxygen dissolved in water, yielding elemental sulfur, which
precipitates out.
Occurrence
Reported found in heated French beans, beef broth, vapors of canned beef, canned beef, beef extract, heated
beef fat, raw beef, beer, bread, heated Brussels sprouts, cabbage, cooked celery, cheddar cheese, cooked and raw chicken, chives,
heated coconut, codfish, ground and roast coffee, heated corn, heated egg, grapefruit juice, cooked herring, citrus juices, strawberry,
cabbage, onion, potato, rutabaga, tomato, blue cheese, buttermilk, raw and boiled eggs, coffee, potato chips, rice, soybeans, okra,
sweet corn, sake, squid, shrimps, cooked, fatty fish and other natural sources
History
Hydrogen sulfide is a colorless, flammable, toxic gas with the characteristic odor of rotten eggs.It is produced naturally from the anaerobic bacterial decomposition of organic wastes, occurs in volcanic gases and hot springs, is a product of animal digestion, and is generated in industrial processes. Hydrogen is a natural component of natural gas and petroleum; it is only a small fraction of oil (hundreds of ppm), but may form an appreciable component of natural gas. Natural gas typically contains up to 5% hydrogen sulfide. Natural gas is considered sour if the hydrogen sulfide content exceeds 5.7 mg of H2S per cubic meter of natural gas. The process for removing hydrogen sulfide from sour gas is referred to as sweetening the gas. Because hydrogen sulfide is associated with anaerobic respiration in sewers and swamps, it is referred to as sewer gas, swamp gas, or stink damp.
Preparation
By far the largest industrial route toH2S occurs in petroleum
refineries. The “hydrodesulfurization” process liberates
sulfur from petroleum by the action of hydrogen. The
resulting H2S is converted to elemental sulfur by partial
combustion via the Claus process that is a major source
of elemental sulfur (In the Claus process, hydrogen
sulfide is catalytically reacted with oxygen from the air
to produce sulfur and sulfur dioxide). Other anthropogenic
sources of hydrogen sulfide include coke ovens,
paper-mills (using the sulfate method), and tanneries,
where Na2S is used for processing cowhide to form
leather. H2S arises from virtually anywhere where
elemental sulfur comes in contact with organic material,
especially at high temperatures.
Production Methods
Hydrogen sulfide is produced during anaerobic respiration (fermentation). Anaerobic respirationenables organisms, primarily bacteria and other microbes, to meet their energy needsusing sulfate, elemental sulfur, and sulfur compounds as electron acceptors instead of oxygen.
Reactions
Fluorine, chlorine, bromine, and iodine react with H2S to form the corresponding halogen acid. Metal sulfides are formed when H2S is passed into solutions of the heavy metals, such as Ag, Pb, Cu, and Mn. This reaction is responsible for the tarnishing of Ag and is the basis for the separation of these metals in classical wet qualitative analytical methods. Hydrogen sulfide reacts with many organic compounds.
Aroma threshold values
Detection: 10 ppb
Purification Methods
Wash it, then pass the gas through a train of tubes containing saturated Ba(OH)2 (2x), water (2x), and dilute HCl [Goates et al. J Am Chem Soc 73 707 1951]. It is available in gas cylinders. HIGHLY POISONOUS.
Flammability and Explosibility
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.
Agricultural Uses
Hydrogen sulphide (H2S) is a colorless, poisonous, flammable gas with an odor of rotting eggs. It is found in cesspools and mines and is a by-product of decomposed substances containing sulphur. It is one of the gaseous end-products of the reduction of sulphate in highly degraded paddy fields. Hydrogen sulphide is also produced in the laboratory for use as an analytical reagent.
Materials Uses
Dry hydrogen sulfide is satisfactorily handled
under pressure at normal ambient temperatures
in carbon steel or black iron piping. Carbon
steels in wet applications are known to be subject
to sulfide stress cracking and low- temperature
brittle fracture under some conditions
of temperature, stress, and pressure. While hydrogen
sulfide itself is relatively noncorrosive to
steel in many uses, factors such as impurities,
pH, erosive conditions, and high thermal or
mechanical stresses in the metal can cause severe
corrosion problems. High-strength steels
are subject to crack formation when exposed to
hydrogen sulfide.
Synthesis
Hydrogen sulfide gas can be formed and released whenever waste containing sulfur is broken down by bacteria.
Potential Exposure
ReproductiveEffector; Human Data. Hydrogen sulfide is used in the syn-thesis of inorganic sulfides, sulfuric acid, and organic sulfurcompounds; as an analytical reagent; as a disinfectant inagriculture; and in metallurgy. It is generated in many industrial processes as a by-product and also during thedecomposition of sulfur-containing organicmatter，sopotential for exposure exists in a variety of situations.Hydrogensulfide is found in natural gas, volcanic gas, andin certain natural spring waters. Its may also be encounteredin the manufacture of barium carbonate, barium salt, cello-phane，depilatories, dyes, pigments, felt, fertilizer, adhe-sives, viscoserayon, lithopone， synthetic petroleumproducts; in the processing of sugar beets; in mining, partic-ularly where sulfide ores are present; in sewers and sewagetreatment plants; during excavation of swampy or filledground for tunnels, wells, and caissons; during drilling ofoil and gas wells; in purification of hydrochloric acid andphosphates; during the low-temperature carbonization ofcoal; in tanneries, breweries, slaughterhouses; in fat render-ing; and in lithography and photoengraving.
Physiological effects
Hydrogen sulfide is a toxic, irritating, and asphyxiant
gas. The substance is known to be produced and metabolized naturally in the human
body at low concentrations, but can be
quickly fatal once the natural bodily defenses
are overwhelmed.
ACGIH recommends a Threshold Limit
Value-Time-Weighted Average (TLV-TWA)
of 10 ppm (14 mg/m3
) for hydrogen sulfide. The
TLV- TWA is the time-weighted average concentration
for a normal 8-hour workday and a
40-hour workweek, to which nearly all workers
may be repeatedly exposed, day after day, without
adverse effect.
ACGIH recommends a Threshold Limit
Value-Short Term Exposure Limit (TLVSTEL)
of 15 ppm (21 mg/m3
) for hydrogen sulfide.
The TLV-STEL is the IS-minute TWA
exposure that should not be exceeded at any
time during a workday even if the 8-hour TWA
is within the TLV- TWA. Exposures above the
TLV- TWA up to the STEL should not be
longer than 15 minutes and should not occur
more than 4 times per day. There should be at
least 60 minutes between successive exposures
in this range.
First aid
If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek med-ical attention immediately. If frostbite has occurred, seekmedical attention immediately; do NOT rub the affectedareas or flush them with water. In order to prevent furthertissue damage, do NOT attempt to remove frozen clothingfrom frostbitten areas. If frostbite has NOT occurred, imme-diately and thoroughly wash contaminated skin with soapand water. If this chemical has been inhaled, remove fromexposure, begin rescue breathing (using universal precau-tions, including resuscitation mask) if breathing has stoppedand CPR if heart action has stopped. Transfer promptly to amedical facility. Medical observation is recommended for24- -48 h after breathing overexposure, as pulmonary edemamay be delayed. As first aid for pulmonary edema, a doctoror authorized paramedic may consider administering a corti-costeroid spray.
Environmental Fate
Hydrogen sulfide is a colorless, flammable compressed liquid
gas with a characteristic odor of rotten eggs. The solubility of
hydrogen sulfide in water is 3980 mg l-1 at 20 ℃ and it is
soluble in certain polar organic solvents, notably methanol,
acetone, propylene carbonate, sulfolane, tributyl phosphate,
various glycols and glycol ethers, gasoline, kerosene, crude
oil, and carbon disulfide. The calculated vapor pressure at
21.9 ℃ is 1929 Pa. Boiling point and melting point of the
substance are -60.33 ℃ and-85.49 ℃, respectively. Based
on the estimated Henry’s law constant of 468 atm mol-1 for
hydrogen sulfide, volatilization from water and soil is high.
storage
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.
Shipping
Hydrogen sulfide requires a shipping label of“POISON GAS, FLAMMABLE GAS.”It falls in HazardClass 2.3. It is a violation of transportation regulations torefill compressed gas cylinders without the express writtenpermission of the owner.
Toxicity evaluation
Toxicity of hydrogen sulfide is most likely related to inhibition
of metal-containing enzymes such as cytochrome oxidase, the
final enzyme of the mitochondrial respiratory chain, and
carbonic anhydrase. Therefore, hydrogen sulfide affects cellular
energy production and respiration. Mucous membranes and
tissues with a high oxygen demand, like nervous and cardiac
tissues are most susceptible tissues in exposure to hydrogen
sulfide. In addition, sulfide also seems to act on the respiratory
drive through other mechanisms such as suppression of synaptic
activity, inhibition of monoamine oxidase, a direct action on
respiratory centers in the brain, and stimulation of the glutamate
receptors in the brain. The hydrosulfide anion also forms
a complex with methemoglobin and creates sulfmethemoglobin.
On the other hand, hydrosulfide can be produced endogenously,
particularly in mammalian cells, through an enzymatic
pathway and in a smaller part via a nonenzymatic pathway.
Among enzymes involved in hydrosulfide production, cystathionine-
synthase and cystathionine-lyase have been investigated
extensively; both use vitamin B6 as a cofactor.
Captopyruvate sulfurtransferase along with cysteine aminotransferase
are involved in transsulfuration and reverse transsulfuration
pathways in different capacities and utilize specific
substrates. Of course, the regulation mechanisms for the
expression and activities of these hydrosulfide-generating
enzymes under physiological or pathophysiological conditions
needs more research. These enzymes are differentially expressed
in neuronal, immune, cardiovascular, renal, gastrointestinal,
reproductive, respiratory, liver, and endocrine systems and affect
the functions of these systems through production of hydrosulfide.
Meanwhile, different molecular targets, such as different
ion channels and signaling proteins, mediate physiological
functions of hydrogen sulfide. Alternations of hydrosulfide
metabolism lead to an array of pathological disturbances in the
form of hypertension, diabetes, cirrhosis, atherosclerosis, heart
failure, inflammation, sepsis, erectile dysfunction, asthma, and
neurodegenerative disease.
Incompatibilities
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. H2S reacts violently with a variety of metal oxides, including the
oxides of chromium, mercury, silver, lead, nickel, and iron.
Waste Disposal
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.
Disposal Excess hydrogen sulfide should be returned to the manufacturer, according to your
institution's waste disposal guidelines. For more information on disposal procedures,
see Chapter 7 of this volume.
GRADES AVAILABLE
Hydrogen sulfide is available in a technical or
commercial grade that is 99 mole percent minimum
hydrogen sulfide. It is also available in
higher purities, up to 99.99 mole percent minimum
hydrogen sulfide.
