some Constants of the Inert Gases. 11 



These numbers he plots against the critical temperature, 

 and obtains a straight line running through argon, krypton, 

 and xenon, which passes very near the origin, but helium is 

 far off the line. 



Since the critical temperatures are now shown to be 

 proportional to the squares of the number of electrons, it 

 follows that for argon, krypton, and xenon, C in Sutherland's 

 equation is nearly proportional to the square of the number 

 of electrons. 



Remarks. 



These results throw additional light on Rankine's discovery 

 that the constant in Sutherland's formula for the temperature 

 coefficient of viscosity is intimately connected with the 

 critical temperature ; and they suggest that the forces which, 

 by acting between the atoms, cause both these phenomena, 

 are to be found in the electric charges of the electrons which 

 influence dispersion. Further they show that there is an 

 intimate relation between the number of electrons in the 

 atoms of these five gases and the radii of their spheres of 

 action at the same temperature. 



One indirect inference may further be noted. Doubts 

 have been felt whether it is permissible to express the 

 refractivity of a gas by a single term of a formula of 

 Sellmeier's type, since this is equivalent to the assumption 

 that the electrons influencing dispersion are all of the same 

 type and have the surne free frequency ; and it was recognized 

 that such a simplification was only tentative. 



The facts that figures derived from this formula can be 

 correlated with others based upon the kinetic theory of gases 

 is evidence that, at least in the case of these gases, the 

 hypothesis is substantially correct. 



Application to other Gases. 



The relations exhibited above cannot be extended to 

 hydrogen, oxygen, or nitrogen. The best agreement is 

 found in the case of the relation between the volumes, as 

 determined from measurements of viscosity and refractivity 

 respectively. The ratio in the case of oxygen is the same as 

 in that of argon, krypton, and xenon, while in that of nitrogen 

 it is not far different. But hydrogen departs widely irom 

 this value. 



It is probable that in the diatomic gases the conditions are 

 more complicated than in the case of the argon group. 



