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The gaseous mixture that is free of oxygen and nitrogen is used for separating the noble gases. This is done using coconut charcoal which adsorbs different gases at different temperatures.

The property of adsorption to coconut charcoal increases with atomic weight of the noble gases. Thus, helium which has the least atomic weight adsorbs the least while xenon with maximum atomic weight adsorbs strongly.

The temperature at which the adsorption takes place increases with the increase in the atomic weight.