Sulphur
Sulfur
or sulphur is a
chemical element with symbol S and
atomic number 16. It is an abundant,
multivalent non-metal. Under normal
conditions, sulfur atoms form cyclic
octatomic molecules with chemical
formula S8. Elemental sulfur is a bright
yellow crystalline solid when at room
temperature. Chemically, sulfur can
react as either an oxidant or reducing
agent. It oxidizes most metals and
several nonmetals, including carbon,
which leads to its negative charge
in most organosulfur compounds, but it
reduces several strong oxidants,
such as oxygen and fluorine.
Sulfur
occurs naturally as the
pure element (native sulfur) and as
sulfide and sulfate minerals. Elemental
sulfur crystals are commonly sought
after by mineral collectors for their
distinct, brightly colored polyhedron
shapes. Being abundant in native
form, sulfur was known in ancient times,
mentioned for its uses in ancient
India, ancient Greece, China and Egypt.
Fumes from burning sulfur were
used as fumigants, and sulfur-containing
medicinal mixtures were used as
balms and antiparasitics. Sulfur is
referenced in the Bible as brimstone
(burn stone) in English, with this name
still used in several nonscientific
tomes. It was needed to make the best
quality of black gunpowder. In 1777,
Antoine Lavoisier helped convince the
scientific community that sulfur
was a basic element, rather than a
compound.
Elemental
sulfur was once extracted
from salt domes where it sometimes
occurs in nearly pure form, but this
method has been obsolete since the late
20th century. Today, almost all
elemental sulfur is produced as a
byproduct of removing sulfur-containing
contaminants from natural gas and
petroleum. The element's commercial uses
are primarily in fertilizers, because of
the relatively high requirement
of plants for it, and in the manufacture
of sulfuric acid, a primary industrial
chemical. Other well-known uses for the
element are in matches, insecticides
and fungicides. Many sulfur compounds
are odoriferous, and the smell of
odorized natural gas, skunk scent,
grapefruit, and garlic is due to sulfur
compounds. Hydrogen sulfide produced by
living organisms imparts the
characteristic
odor to rotting eggs and other
biological processes.
Sulfur
is an essential element
for all life, and is widely used in
biochemical processes. In metabolic
reactions, sulfur compounds serve as
both fuels and respiratory
(oxygen-alternative)
materials for simple organisms. Sulfur
in organic form is present in the
vitamins biotin and thiamine, the latter
being named for the Greek word
for sulfur. Sulfur is an important part
of many enzymes and in antioxidant
molecules like glutathione and
thioredoxin. Organically bonded sulfur
is
a component of all proteins, as the
amino acids cysteine and methionine.
Disulfide bonds are largely responsible
for the mechanical strength and
insolubility of the protein keratin,
found in outer skin, hair, and feathers,
and the element contributes to their
pungent odor when burned.
Sulfur Piles on Wharf in Vancouver, Canada. Credit: Ted McGrath
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