Wed February 19, 2014
The first person to actually isolate and note the presence of these noble gases was Henry Cavendish.
He removed all the nitrogen and oxygen chemically from a receptacle containing air. The nitrogen was oxidised to NO2 by electric discharges and absorbed by a sodium hydroxide solution. Remaining oxygen was removed from the mixture by a special adsorber. 1/120 of the gas volume remained unreacted in the receptacle. As we know today, this must have been mainly argon (99.8%) and traces (0.2%) of other noble gases.
Two reasons for late discoveries of noble gases are:
1. They are present in extremely low concentrations in our environment.
2. They are very inert.