QS Study

The mixture of noble gases obtained by the above method is separated into individual constituents by the use of coconut charcoal which adsorbs different gases at different temperatures.

Fig: Separation of noble gases (Dewar’s method)

The mixture of noble gases is passed into a double-walled bulb containing coconut charcoal and placed in a low-temperature bath at 173K. It is allowed to remain in contact with the charcoal for about half an hour. At 173K, only argon, krypton and xenon are adsorbed by the charcoal while helium and neon remain unadsorbed. These are pumped out and collected.

The mixture of helium and neon is kept in contact with coconut charcoal at 93K which completely adsorbs neon leaving free helium.

The charcoal at 173K containing argon, krypton and xenon is placed in contact with another charcoal at the temperature of the liquid air when argon diffuses into the other charcoal.

The temperature of the first charcoal (temp.173K) still containing krypton and xenon is raised to 183K when Krypton is set free while xenon remains adsorbed in the charcoal. When it is heated, xenon is recovered.