| Silicon
is a woman's dream element. It is used in hair care, skin care, and
nail care treatments. It also makes your skin firmer so you don't
get wrinkles. |
Silicon is the second most abundant element and it makes up about 28% of
the earth's crust. Pure Silicon is a hard, dark gray solid and has
a metallic luster. When it is combined with oxygen it forms silicon
dioxide. This is called Silica. Silica is the main ingredient
in sand. Sand is used in glass. Some times when combined with
Oxygen, it forms a rock. The use of silica to produce glass-like
materials in decorative items dates back as far as 1500 B.C. By the
end of the 18th century, chemists understood that there was some sort of
common link between sand, quartz, and silica. In 1824, by heating chips
of potassium metal in a container of silica (silicon tetra fluoride), silicon
was produced in a mixture of potassium fluoride. When the potassium
fluoride was chemically separated, silicon was isolated and identified
in a fairly high quality sample. Silicon is the most abundant solid
element, being second only to oxygen. Silicon makes up more than
25% of the earth's crust. It is a semi metal, or metalloid. It rarely
occurs in elemental form, virtually all of it existing as compounds. Silicon
is best known in two forms:
1.a dark brown, powdery amorphous form, which is best known for
its presence as beach sand.
2.a gray, metallic looking crystalline form, which is best known
for its impact upon modern civilization
- as the foundation material for electronic
semiconductor components.
Other commercial applications of silicon include:
1. Glass making:
Calcium and sodium silicates,
Na2SiO3.CaSiO3.3SiO2, or soda glass that is used in ordinary
glasses, bottles and windows.
It is made by fusing sand (SiO2), sodium carbonate and
limestone (CaCO3) at about 1400oC.
Pyrex glass, which is used for
laboratory equipment and ovenware, has a higher softening
temperature and is resistant to
sudden changes of temperature because it has a smaller thermal
coefficient of expansion. In this
type of glass the proportion of CaSiO3 is lower and some silica
is replaced by boron trioxide,
B2O3.
Colored glass has small amounts of other ions such as:
green chromium(III),
violet manganese(IV),
blue cobalt(II), or
brown iron(III).
Crystal glass used for high grade
tableware and chandeliers contains some lead oxide. This
glass has a higher refractive
index than ordinary glass. This causes it to "sparkle" since the
pieces are cut at such angles
that total internal reflection and spectral dispersion of light occur.
2. Sodium silicate, Na2SiO3, which is known as water glass.
It is a silicon compound that dissolves in
water. It is produced by reacting
silicon dioxide with sodium hydroxide at a high temperature. The
thick clear liquid which results
has a wide range of viscosity according to water content. The major
uses of water glass are as a dispersing
agent for clay suspensions, as a fire-retardant coating for
paper and fiberboard, and as a
detergent, soap and adhesive builder. Silica gel is a porous solid
material made by treating sodium
silicate with sulfuric acid. It is used as a dehumidifier or a
desiccant.
3. Aluminosilicate minerals or zeolite, which exhibit
ion exchange properties are used for water
softening.
4. Silicon carbide, SiC or carborundum, which is a tough,
abrasive substance that is used for grinding
metals. It is a dark, bluish black
crystal that is produced by heating sand and coke (carbon) together
in an electric furnace.
5. Silicon tetrachloride, SiCl4, which is used by the
military for generating smoke screens from dense
clouds of white vapor.
6. Silicon tetra fluoride, sift, is a colorless, choking
gas that is mainly used in production of other
fluorosilicates.
7. Portland cement, which is a complex mixture of calcium
silicates and aluminosilicates.
8. Silicones are polymeric synthetic silicon compounds.
Silicones are used as lubricants and water
repellents and in waxes and varnishes.
Silicone rubbers are superior to natural rubbers in their
resistance to both high and low
temperatures and chemicals. |
