Relation between Viscosity and Atomic Weight for Gases. 45 



to repeat the observations with different values of V x and V 2 , 

 and, consequently, different values of v. The method may 

 also be applied to the determination of the capacity of con- 

 densers designed to serve as secondary standards. These 

 condensers can be used as "auxiliary" condensers, and the 

 determination of their capacities will have the same accuracy 

 whatever the ratio of those capacities to that of the measuring 

 system. 



It is found in practice that it is quite easy to attain such 

 accuracy that the probable error of the value deduced from 

 a single observation is not greater than 1 per cent. 



Leeds, September 1910. 



VII. On the Relation between Viscosity and Atomic Weight 



for the Inert Gases ; with its Application to the case of 



Radium Emanation. By A. 0. Rankine, D.Sc, Assistant 



in the Department of Physics, University of London, 



University College *. 



A FURTHER examination of the data obtained in my 

 measurements of the viscosities of the gases of the 

 argon group f has brought to light a simple relation between 

 viscosity and atomic weight. This relation has some im- 

 portant applications. It may be used, as will be shown, to 

 form an estimate of the critical temperature of neon. 

 Further, in conjunction with another relation previously 

 published, it renders possible the estimation of the viscosity 

 and molecular dimensions of radium emanation, upon the 

 assumption that this gas belongs to the argon group. 



The data upon which the present paper is based are given 

 in Table I. 



Table I. 



Gas. 



*? xKr\ 



C. 



He 



1-879 

 2-981 

 2-102 

 2-334 

 2-107 



70 



56 



142 



18S 

 252 



Ne 



A 



Kr 



X 





* Communicated by Prof. F. T, Trouton, F.R.S. 

 t Ti-oe. Roy. Soc. A, vol. lxxxiii. p. 516, and Proc. Roy. Soc. A, 

 vol. lxxxiv. p. 181. 



