FAQs about chlorine and caustic soda
Chlorine is used in a vast range of processes to create
thousands of indispensable products. Chlorine is everywhere. If you
drink a glass of water, take medicine, clean your teeth or drive to
work you are benefiting from chlorine compounds. Even your body's
own digestive system depends upon a chlorine compound (hydrochloric
acid) to break down foodstuffs. Caustic soda is equally important
in many industrial sectors.
Read more about uses of chlorine.
Read more about the uses of caustic
soda.
Here are some frequently asked
questions about this amazing element.
For further interesting information on the chlor-alkali
industry, go to our facts and figures
section.
If you have a question relating to the chlor-alkali
industry, contact Euro Chlor
communications.
Was chlorine discovered or
invented?
Chlorine was discovered by Carl W. Scheele (1742-1786) in 1774
but it was not yet known as an element. Due to its strong oxidising
properties it was thought by most chemists to contain oxygen and
was called oxymuriatic acid (muriatic acid being HCl or
hydrochloric acid).
More information about C.
W. Scheele on chemistryexplained.com
It was Humphry Davy (1778-1829) who exposed the gas to white-hot
carbon in an attempt to remove the oxygen as carbon dioxide. He was
never able to produce oxygen or any compound known to contain
oxygen, and he finally concluded that chlorine had to be an
element. Because of its greenish yellow colour, he called it
"chlorine" after the Greek "chloros" meaning yellow-green.
Can chlorine be found in
nature?
Chlorine (one element of the 'halogen' group) has an established
place in the natural world: the sea, plants and animals all contain
and produce vast amounts of chlorinated molecules. In the human
body itself, chlorinated compounds are indispensable to the
functioning of the vital organs. For example, hydrochloric acid
plays a key role in the digestive process: in YOUR stomach! Click
on Amazing Organohalogens to find out more about where these
chemicals occur naturally.
What is the main use of
chlorine?
The chief application of chlorine is in the manufacture of PVC.
Thirty-five percent of the chlorine produced in Europe is used to
make this versatile product. PVC is used in 25% of medical devices
including blood bags, sterile tubing, catheters and prosthetics. It
is also a key material in the construction sector: used for window
frames, roller shutters, water pipes, floor coverings etc.
After PVC, probably the most well known application of chlorine
is for disinfection of drinking water and swimming pool water. The
purification of drinking water is vital to minimise the often
devastating impact of waterborne diseases such as typhoid, cholera,
dysentery and gastroenteritis. These have killed more people than
all the wars in history. As a disinfectant, chlorine saves
lives.
Read more about uses of chlorine.
What other uses does
chlorine have?
Chlorine is a key chemical building block and is, therefore,
used in the manufacture of many products. Although chlorine
chemistry is used in many manufacturing processes, it is not always
in the end product. A third of all chlorine produced in Europe is
used to make productsnotcontaining chlorine.
Chlorine is in bleach (sodium hypochlorite) which is used to
combat microbes and contagious diseases, particularly in
hospitals.
An example of a process involving chlorine chemistry, but where
no chlorine occurs in the end product, is the production of silicon
of 99.99% purity. This is needed to produce microchips. A similar
purity is necessary for solar cells. To achieve such purity
requires a complicated purification process. The most commonly used
method is to react 98% pure silicon with hydrochloric acid to make
trichlorosilane. This is vaporized and then condensed in
distillation columns until all other substances are removed.
Finally, the trichlorosilane vapour is conducted with hydrogen
across heated silicon rods. The ultrapure silicon is deposited, and
the hydrogen chloride that forms as a by-product can be returned to
the production process.
Polyurethanes (your shoe soles!) and polycarbonates (your car
headlights) are also examples of widely used materials produced
using chlorine chemistry, but where chlorine does not occur in the
end product. Applications of polyurethanes include the manufacture
flexible and rigid foams, coatings, adhesives and sealants. Because
of their extreme toughness and transparency, polycarbonates are
used in the production of many everyday items such as computers,
soft drinks bottles and CDs.
How is chlorine made?
Essentially, chlorine is made by passing an electric current
through salt water (brine). There are three main production routes:
the membrane, the mercury and the diaphragm process. Although most
chlorine in Europe is now already manufactured using the membrane
process, the industry is committed to converting mercury
production units to the more environmentally-sound membrane process
by 2020.
Read more about the membrane, the mercury and the diaphragm
process.
How much chlorine and
caustic soda is produced every year in Europe?
In 2010 the European chlor-alkali industry produced 19.8 million
tonnes of chlorine and caustic soda. As our product is a key
industrial building block used to create products in many sectors,
production levels of chlorine act as a reliable barometer of the
economy.
What else
is produced in the chlorine manufacturing process?
When chlorine is produced, caustic soda (otherwise known as
sodium hydroxide - NaOH) and hydrogen (H2) are formed as
co-products. For every tonne of chlorine made, 1.1 tonnes of
caustic soda (100%) and 0.03 tonnes of hydrogen are produced.
What is caustic
soda used for?
More than half of caustic soda produced is used in the chemical
industry and the rest for the manufacture of products such as soap
and detergents, textiles, paints, glass and ceramics. It is also
used in water treatment, aluminium production and oil
refining.
Read more about the uses of caustic
soda.
How many people work
in the chlorine industry?
The industry employs directly about 39,000 people in Europe.
However, almost 2,000,000 jobs are related to chlorine.
Is
chlorine beneficial to human health?
Chlorine is essential for a healthy human life. It is vital for
water disinfection and sewage and industrial effluent treatment.
Eighty-five percent of medicines either contain chlorine or use
chlorine in the production process. Chlorine is also an essential
intermediate in the production of certain materials used for making
medical equipment such as silicone rubber which insulates the
electrodes and catheters in a pacemaker, PVC blood bags and sterile
tubing. Water disinfection is another application in which chlorine
plays a vital role.
Last update : 09/2011
