146 



SIR WILLIAM EAMSAY 



element predicted for the position between helium and 

 argon. A gas named metargon, announced at the same 

 time, proved afterwards to be a mixture containing 

 carbonic oxide. By allowing a large quantity of liquid 

 air to evaporate quietly, and removing oxygen and 

 nitrogen from the residue, a mixture of argon and krypton 

 was obtained, in which was detected yet another gas in 

 small quantity, to which the name xenon (the stranger) 

 was given. All these gases agree with argon in chemical 

 inactivity and in consisting of monatomic molecules. 

 Their densities, boiling points, critical temperatures and 

 pressures, refractivities and spectra have been examined 

 and recorded, and the " Companions of Argon " form a 

 complete series running parallel with the halogen 

 elements on the one side and with the alkali metals on 

 the other, as shown below : 



Here the atomic weights are given in round numbers, 

 but when the most accurate determinations of the 

 atomic weight of argon are compared with those of 

 potassium, the figure for the former element is still too 

 great Taking the atomic weights given in the most 



