Nobel Gases - a little more about them
The first person to discover the noble gases was Henry Cavendish in 1875. Cavendish distinguished these elements by chemically removing all oxygen and nitrogen from a container of air. The nitrogen was oxidized to NO2 by electric discharges and absorbed by a sodium hydroxide solution. The remaining oxygen was then removed from the mixture with an absorber. The experiment revealed that 1/120 of the gas volume remained un-reacted in the receptacle. The second person to examine them was William Francis, he noted the formation of gas while dissolving uranium minerals in acid.