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  • Created on: 20-10-11 16:07

Useful Products from Air & Salt.

Fractional distillation of air produces nitrogen and oxygen. Air is made up mainly of two gases: nitrogen (78%) and oxygen (21%). The other 1% is mainly argon but there is also carbon dioxide, water vapour and other gases. Nitrogen and oxygen can be separated by fractional distillation- this relies on the fact that the two gases boil at different temperatures. (Nitrogen at –196 and oxygen at –187). Air is first cooled by repeatedly compressing and expanding it, until it liquefies at about –200. As the air warms up, nitrogen boils first. Oxygen is used for oxy-acetylene welding; in rocket engines; to make other chemicals; in hospitals etc. Nitrogen is used to make ammonia, which is then used to make fertilizers; to provide an unreactive atmosphere and liquid nitrogen is used to keep things cold or in the drilling of crude oil.

Salt is taken from the sea and underground.

In hot countries the pour salt water into big open tanks and let the sun evaporate the water to leave salt. This is no good in cold countries as there is not enough sunshine. In these countries salt in extracted from underground deposits left millions of years ago when ancient seas evaporated. There are massive deposits of rock salt in Cheshire. Rock salt is mainly a mixture of sand and salt. It can be used in its raw state on roads or the sand can be filtered out of the mixture to leave refined salt.

The salt in the mixture melts ice but lowering the freezing point of water to –5. The sand and grit also give grip on melted ice.

Refined salt is added to most processed foods to enhance the flavour but it is unhealthy to have too much salt.


Salt is used to make chemicals and is important in the chemical in the chemical industry. Firstly they electrolyse sodium chloride solution, which splits the solution into hydrogen, chloride and sodium hydroxide. Sodium can be extracted from molten sodium chloride. All the products are collected and used.

Chloride is used in bleach; for sterilising water; for making hydrochloric acid and insecticides. Also used to make plastics, pesticides; weed killers; pharmaceuticals etc.

Hydrogen is used in the Haber process to make ammonia; to change oils into fats for making margarine. Also used as a fuel in fuel cells and for welding or metal cutting.

Sodium is used to make detergents and lots of other organic chemicals. Its also used in the extraction of titanium and as a coolant for some nuclear reactors.

Sodium hydroxide is a very strong alkali and is widely used in the chemical industry to make soap ceramics, organic chemicals, paper pulp, oven cleaner, drain blocker etc. Also used to in the aluminium extraction.


Fractional distillation of Crude oil.

Crude oil is formed from the buried remains of plants and animals- it’s a fossil fuel. Over millions of years, with high temperature and pressure, the remains turn to crude


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