Encyclopedia
Sulfur or
sulphur is the
chemical element in the periodic table that has the symbol
S and atomic number 16. It is an abundant, tasteless, odorless, multivalent non-metal. Sulfur, in its native form, is a yellow crystaline solid. In
nature, it can be found as the pure element or as sulfide and
sulfate minerals. It is an essential element for life and is found in two
amino acids. Its commercial uses are primarily in
fertilizers but it is also widely used in
gunpowder,
matches, insecticides and fungicides.
Notable characteristics
At room temperature, sulfur is a soft bright yellow solid. Although sulfur is infamous for its smell—frequently compared to rotten eggs—the odor is actually characteristic of
hydrogen sulfide ; elemental sulfur has a faint odor similiar to matches. It burns with a blue flame that emits
sulfur dioxide, notable for its peculiar suffocating odor. Sulfur is insoluble in water but soluble in
carbon disulfide and to a lesser extent in other organic solvents such as
benzene. Common
oxidation states of sulfur include −2, +2, +4 and +6. Sulfur forms stable compounds with all elements except the noble gases.
Sulfur in the solid state ordinarily exists as cyclic crown-shaped S
8 molecules. Sulfur has many
allotropes besides S
8. Removing one atom from the crown gives S
7, which is responsible for sulfur's distinctive yellow color. Many other rings have been prepared, including S
12 and S
18. By contrast, its lighter neighbor
oxygen only exists in two states of allotropic significance: O
2 and O
3.
Selenium, the heavier analogue of sulfur can form rings but is more often found as a polymer chain.
The crystallography of sulfur is complex. Depending on the specific conditions, the sulfur
allotropes form several distinct
crystal structures, with
rhombic and
monoclinic S
8 best known.
A noteworthy property is that the
viscosity of molten sulfur, unlike most other liquids, increases with temperature due to the formation of
polymer chains. However, after a specific temperature is reached, the viscosity is reduced because there is enough energy to break the chains.
Amorphous or "plastic" sulfur can be produced through the rapid cooling of molten sulfur.
X-ray crystallography studies show that the amorphous form may have a
helical structure with eight atoms per turn. This form is
metastable at room temperature and gradually reverts back to crystalline form. This process happens within a matter of hours to days but can be rapidly catalyzed.
Applications
Sulfur has many industrial uses. Through its major derivative,
sulfuric acid , sulfur ranks as one of the more important industrial raw materials. It is of prime importance to every sector of the world's economies.
Sulfuric acid production is the major end use for sulfur, and consumption of sulfuric acid has been regarded as one of the best indices of a nation's industrial development. More sulfuric acid is produced in the
United States every year than any other industrial chemical.
Sulfur is also used in batteries,
detergents, the
vulcanization of rubber, fungicides, and in the manufacture of
phosphate fertilizers. Sulfites are used to
bleach paper and as a preservative in
wine and dried
fruit. Because of its flammable nature, sulfur also finds use in
matches,
gunpowder, and
fireworks. Sodium or ammonium
thiosulfate is used as photographic fixing agents.
Magnesium sulfate, better known as
Epsom salts, can be used as a laxative, a bath additive, an exfoliant, or a
magnesium supplement for plants. Sulfur is used as the light-generating medium in the rare lighting fixtures known as
sulfur lamps.
In the late 1700s,
furniture makers used molten sulfur to produce decorative
inlays in their craft. Because of the
sulfur dioxide produced during the process of melting sulfur, the craft of sulfur inlays was soon abandoned.
Biological role
The
amino acids
cysteine and
methionine contain sulfur, as do all polypeptides,
proteins, and
enzymes which contain these amino acids. This makes sulfur a necessary component of all living cells.
Disulfide bonds between polypeptides are very important in protein assembly and structure.
Homocysteine and
taurine are also sulfur containing amino acids but are not coded for by
DNA nor are they part of the
primary structure of proteins. Some forms of
bacteria use
hydrogen sulfide in the place of water as the
electron donor in a primitive
photosynthesis-like process. Sulfur is absorbed by
plants via the
roots from soil as the
sulfate ion and reduced to sulfide before it is incorporated into
cysteine and other organic sulfur compounds . Inorganic sulfur forms a part of iron-sulfur clusters, and sulfur is the bridging ligand in the
CuA site of
cytochrome c oxidase. Sulfur is an important component of coenzyme A.
Environmental impact
The burning of
coal and
petroleum by industry and power plants liberates huge amounts of
sulfur dioxide which reacts with atmospheric water and oxygen to produce
sulfuric acid. This sulfuric acid is a component of
acid rain, which lowers the
pH of
soil and freshwater bodies, resulting in substantial damage to the
natural environment and
chemical weathering of statues and architecture. Fuel standards increasingly require sulfur to be extracted from
fossil fuels to prevent the formation of acid rain. This extracted sulfur is then refined and represents a large portion of sulfur production.
History
Sulfur was known in ancient times, and is referred to in the
Biblical Pentateuch . The word itself is almost certainly from the
Arabic sufra meaning yellow, from the bright color of the naturally occurring form.
English translations of the Bible commonly refer to sulfur as "brimstone", giving rise to the name of 'Fire and brimstone'
sermons, in which listeners are reminded of the fate of eternal damnation that awaits the nonbelieving and unrepented. It is from this part of the Bible that
Hell is implied to "smell of sulfur", although as mentioned above sulfur is in fact odorless. The "smell of sulfur" usually refers to the odor of
hydrogen sulfide, e.g. from rotten eggs. Burning sulfur produces
sulfur dioxide, the smell associated with burnt matches.
Homer mentioned "pest-averting sulfur" in the 8th century BC and in 424 BC, the tribe of
Boeotia destroyed the walls of a city by burning a mixture of coal, sulfur, and tar under them. Sometime in the
12th century, the
Chinese invented
gun powder which is a mixture of potassium nitrate ,
carbon, and sulfur. Early
alchemists gave sulfur its own alchemical symbol which was a triangle at the top of a cross. In the late 1770s,
Antoine Lavoisier helped convince the scientific community that sulfur was an element and not a compound. In 1867, sulfur was discovered in underground deposits in
Louisiana and
Texas. The overlying layer of earth was
quicksand, prohibiting ordinary mining operations. Therefore the Frasch process was utilized.
Occurrence
Elemental sulfur can be found near
hot springs and
volcanic regions in many parts of the world, especially along the
Pacific Ring of Fire. Such volcanic deposits are currently exploited in
Indonesia,
Chile, and
Japan.
Significant desposits of elemental sulfur also exist in
salt domes along the coast of the
Gulf of Mexico, and in
evaporites in eastern Europe and western Asia. The sulfur in these deposits is believed to come from the action of anaerobic bacteria on
sulfate minerals, especially
gypsum. Such deposits are the basis for commercial production in the
United States,
Poland,
Russia,
Turkmenistan, and
Ukraine.
Sulfur extracted from oil, gas and the
Athabasca Oil Sands has become a glut on the market, with huge stockpiles of sulfur in existence throughout Alberta.
Common naturally occurring sulfur compounds include the metal sulfides, such as
pyrite ,
cinnabar ,
galena ,
sphalerite and
stibnite ; and the metal sulfates, such as gypsum ,
alunite , and
barite . It occurs naturally in volcanic emissions, such as from
hydrothermal vents, and from bacterial action on decaying sulfur-containing organic matter.
The distinctive colors of
Jupiter's
volcanic moon, Io, are from various forms of molten, solid and gaseous sulfur. There is also a dark area near the
Lunar crater Aristarchus that may be a sulfur deposit. Sulfur is also present in many types of
meteorites.
See also , .Compounds
Hydrogen sulfide has the characteristic smell of rotten eggs. Dissolved in water, hydrogen sulfide is acidic and will react with metals to form a series of metal sulfides. Natural metal sulfides are common, especially those of iron. Iron sulfide is called
pyrite, the so called
fool's gold. Interestingly, pyrite can show semiconductor properties.
Galena, a naturally occurring lead sulfide, was the first
semiconductor discovered, and found a use as a signal
rectifier in the "cat's whiskers" of early
crystal radios.
Many of the unpleasant odors of organic matter are based on sulfur-containing compounds such as
methyl and
ethyl mercaptan used to scent natural gas so that leaks are easily detectable. The odor of
garlic and "
skunk stink" are also caused by sulfur-containing organic compounds. However, not all organic sulfur compounds smell unpleasant; for example,
grapefruit mercaptan, a sulfur-containing
monoterpenoid is responsible for the characteristic scent of
grapefruit.
Polymeric sulfur nitride has metallic properties even though it does not contain any
metal atoms. This compound also has unusual electrical and optical properties. This polymer can be made from
tetrasulfur tetranitride S
4N
4.
Phosphorus sulfides are important in synthesis. For example, P
4S
10 and its derivatives
Lawesson's reagent and
naphthalen-1,8-diyl 1,3,2,4-dithiadiphosphetane 2,4-disulfide are used to replace oxygen from some organic molecules with sulfur.
Inorganic sulfur compounds:...
which is generated by dissolving SO
2 in water. Sulfurous acid and the corresponding sulfites are fairly strong reducing agents. Other compounds derived from SO
2 include the pyrosulfite or metabisulfite ion .
...
S
4N
4 is an example.
...
s contain the SCN
- group. Oxidation of thiocyanoate gives thiocyanogen,
2 with the connectivity NCS-SCN.
Organic sulfur compounds :
- Thioethers have the form R-S-R′. These compounds are the sulfur equivalents of ethers.
- Sulfonium ions have the formula RR'S-'R'", i.e. where three groups are attached to the cationic sulfur center. Dimethylsulfoniopropionate is a sulfonium ion, which is important in the marine organic sulfur cycle.
- Thiols have the form R-SH. These are the sulfur equivalents of alcohols.
- Thiolates ions s have the form R-S-. Such anions arise upon treatment of thiols with base.
- Sulfoxides have the form R-S-R′. A common sulfoxide is DMSO
...
.
- Sulfones have the form R-S2-R′. A common sulfone is sulfolane C4H8SO2.
See also and organosulfur chemistryIsotopes
Sulfur has 18 isotopes, of which four are stable:
32S ,
33S ,
34S , and
36S . Other than
35S, the
radioactive isotopes of sulfur are all short lived.
35S is formed from
cosmic ray spallation of
40Ar in the
atmosphere. It has a half-life of 87 days.
When sulfide
minerals are precipitated, isotopic equilibration among solids and liquid may cause small differences in the dS-34 values of co-genetic minerals. The differences between minerals can be used to estimate the temperature of equilibration. The d
C-13 and dS-34 of coexisting carbonates and sulfides can be used to determine the
pH and
oxygen fugacity of the ore-bearing fluid during ore formation.
In most
forest ecosystems, sulfate is derived mostly from the atmosphere; weathering of ore minerals and evaporites also contribute some sulfur. Sulfur with a distinctive isotopic composition has been used to identify pollution sources, and enriched sulfur has been added as a tracer in
hydrologic studies. Differences in the natural abundances can also be used in systems where there is sufficient variation in the
34S of ecosystem components.
Rocky Mountain lakes thought to be dominated by atmospheric sources of sulfate have been found to have different dS-34 values from lakes believed to be dominated by watershed sources of sulfate.
Precautions
Carbon disulfide, carbon oxysulfide, hydrogen sulfide, and sulfur dioxide should all be handled with care.
Although
sulfur dioxide is sufficiently safe to be used as a food additive in small amounts, at high concentrations it reacts with moisture to form
sulfurous acid which in sufficient quantities may harm the
lungs, eyes or other tissues. In creatures without lungs such as insects or plants, it otherwise prevents respiration.
Hydrogen sulfide is quite
toxic . Although very pungent at first, it quickly deadens the sense of smell, so potential victims may be unaware of its presence until it is too late.
Spelling
The element has traditionally been spelled
sulphur in the
United Kingdom,
Ireland,
Hong Kong and
India, but
sulfur in the
United States, while both spellings are used in
Australia,
Canada and
New Zealand.
IUPAC adopted the spelling "sulfur" in 1990, as did the
Royal Society of Chemistry Nomenclature Committee in 1992. This spelling has begun to replace its variant in official use, unlike
aluminum, which is not commonly used outside
North America, and which
IUPAC rejected in 1990 in favor of
aluminium.
The Latin name of the element is
sulfur with an F. Since it is an original Latin name and not a Classical Greek loan, the fricative phoneme is indeed denoted with
f rather than
ph . Sulfur in Greek is
thios , which does not bear resemblance to the Latin word.
Fire and brimstone
Christian countries often associate sulfur, with
Hell and divine wrath, mostly due to the phrase "fire and brimstone", which occurs in the
Bible in descriptions of Hell and divine punishment. "Fire and brimstone" sermons are those used by charismatic preachers to compel belief by depictions of the horrors of Hell and its punishments. A joke among scientists has used those descriptions of Hell to conclude that, whereas
Heaven's temperature would be a scorching 525 degrees Celsius Hell can be no hotter than the boiling point of brimstone , and thus cannot be as hot as Heaven.
See also
References
-
- R. Steudel : Elemental Sulfur and Sulfur-Rich Compounds , Topics in Current Chemistry Vol. 230 & 231, Springer, Berlin 2003.
External links
