Page 10 - Curriculum Visions Dynamic Book

Chlorine
Chlorine is a greenish-yellow gas (the name chlorine in Greek means greenish-yellow), which is more dense than air and which will dissolve to some extent in water. It forms an amber-coloured liquid at its boiling point.
Nearly one-fiftieth of sea water is made of chlorine, where it occurs combined with sodium as sodium chloride.
People become sensitive to the presence of chlorine in concentrations as little as three to five parts per million because it irritates the membranes of the nose. At concentrations of 30 parts per million its effects on the eyes and nose become severe. At only slightly higher concentrations, it causes difficulty in breathing.
Like other halogens, chlorine is a very reactive substance and it is never found as a free element in nature. It is particularly reactive in the presence of heat, and although it does not dissolve well in water, it does react in the presence of moisture.
It is particularly reactive with organic substances, sometimes causing explosions. For these reasons chlorine needs to be kept in dry, cool conditions.
A flame will continue to burn in a vessel containing chlorine gas. Many products containing chlorine (such as PVC, polyvinyl chloride) will decompose when heated. If used extensively for home furnishings, for example, these materials can be a major hazard during a fire.
Chlorine is one of the ten most important industrial chemicals. The success of an industrial country is sometimes measured in the amount of chlorine its chemical factories use!
Laboratory preparation
of chlorine
A gas jar of chlorine gas
is prepared by reacting concentrated hydrochloric acid on potassium permanganate crystals. Chlorine
is heavier than air, so it can be allowed to collect at the bottom of a gas jar, forcing the air out of the top.
 A representation of a chlorine gas molecule.
Dangers of chlorine
Transporting chlorine can
be a health hazard. If the transporting vessel is involved in an accident and the chlorine escapes to the atmosphere, many people might have their lungs damaged or even be killed. For this reason chlorine is not usually transported; instead other chemicals are brought to where the chlorine is made. This is the case, for example, with making the common plastic PVC. A material called ethene is brought to the chlorine plant to be reacted with the chlorine. The product is shipped off to be further manufactured elsewhere.
Also...
When large amounts of waste hydrochloric acid are available –
for example, when PVC is being made – the chlorine can often be recovered and recycled by oxidising the acid.
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