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Without helium, it would be impossible to reach temperatures close to absolute zero. Helium is the simplest of the noble gases - chemically inert, odour-less and colourless, non-flammable, non-toxic. At normal pressure it can be used without the necessity for any special safety precautions. Its most important property for this application is that it boils at 4.22 K and does not freeze.It is very much lighter than air and when liquefied weighs only 125 g / l. To obtain one litre of liquid helium, however, some 699 liters of the gas are needed. This figure makes it clear that helium is always stored in liquid form if at all possible, since it takes up far less space in this form.The raw material for the production of helium is natural gas. Natural gas is a mixture that occurs either on its own or together with crude oil within the Earth's crust. The process for extracting helium from a helium-rich natural gas is described next. In the first step, carbon dioxide and moisture are removed from the natural gas. By cooling the pre-purified gas to approx. 214 K (-55°C), partial condensation of the benzene fraction is achieved. A further drop in temperature leads to condensation of the CH4-NH2 fraction, which is broken down in a column into pure CH4 ( methane ) and N2 (nitrogen). By further temperature reductions and adsorption, the remaining CH4 and N2 is removed from the remaining crude helium. In a final stage, the gaseous helium is liquefied. Helium-rich deposits of natural gas are found in the USA, North Africa and Poland. From the regions where it is produced, helium is shipped in liquid form in large containers to Western Europe, where it is distributed to industrial gas marketing companies. Today the final consumer in Germany has to pay approx. 4,00 EURO to 6,00 EURO per cubic metre of helium gas.

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