338 Albert P. Mathews 



a union of argon with zinc, mercury and some other elements. 

 Thus in a Pliicker tube the cathode metal disintegrates more 

 rapidly when argon under low pressure is in the tube than 

 when nitrogen is there, and Ramsay interprets this to mean 

 that a volatile compound is formed under the influence of the 

 intense energy at the surface of the electrode and this com- 

 pound dissociates again setting free the metal, which deposits 

 on the glass. Under his direction C. Trenton Cooke 1 measured 

 the vapor tension of zinc, cadmium, sulfur, mercury and some 

 other metals at high temperatures in the presence of various 

 gases and concluded that the tension of zinc in argon was 

 12 percent above its tension in nitrogen. Cadmium behaved 

 similarly in helium. Helium seems to be in some kind of a 

 union in fergusonite, and to be capable of feebly uniting with 

 platinum. It may be recalled, also, that the solubility of 

 argon in water is greater than that of helium and nitrogen; 

 and this may be urged as indicating some kind of affinity 

 between water and argon. Chemically, then, these gases, 

 though inert, are not entirely indifferent. 



From their action on light, 2 also, a certain argument may 

 be made for their possessing valence. Thus, according to 

 Drude, the dispersion of light in the blue end of the spectrum 

 is due to the valence electrons, and in the red end to the 

 vibrations of the electrically charged atomic groups. If only 

 the valence electrons affect blue light, these gases must also 

 have valence electrons, since they refract light like other gases. 



The question whether these elements have valence, or 

 not can be put to a decisive test through their molecular 

 cohesions. 3 There is no question that they possess cohesion, 

 since they can all be liquefied. They behave like all other 

 gases in this respect. Molecular cohesion in all other sub- 

 stances examined is a function of the product of the molecular 

 weight by the number of valences. It has been shown for a 



1 C. Trenton Cooke: Loc. cit., p. 537. 



2 Cuthbertson, C.: "Refractive Indices of the Elements," Phil. Trans., 

 204, 323 (1904). 



3 Mathews: Jour. Phys. Chem., 17, 181 (1913). 



