L 69 ] 



XL New Determinations of some Constants of the Inert 

 Gases. By Olive Cuthbertson, Fellow of University 

 College, London* . 



IN a recent paper in the Philosophical Magazine, Dr. Gr. 

 Rudorf t calculated some of the molecular constants of 

 the inactive gases with the object of seeing how fur the values 

 obtained by various methods agreed among themselves. The 

 results were disappointing. 



Since that time three papers % on the physical properties 

 o£ these gases have provided additional data for their study, 

 and a comparison of these figures, obtained by different 

 methods, points to some interesting conclusions. 



Relation between Determinations of Volume of 

 Molecules from Viscosity and Refract ivity. 



On certain assumptions it is possible to calculate the 

 volume occupied by the atoms of a gas both from the vis- 

 cosity and from the refractivity. 



We find in Rankine's first paper the first complete set of 

 measurements of the viscosity of the five inert gases. The 

 experiments were made at atmospheric tempeniture, with 

 the same apparatus under similar conditions. The results 

 are therefore of high value. 



Rankine gives the figures shown in the first columns of the 

 table below for the relative viscosity, mean free path, and 

 molecular radius of the five gases, taking the figures for 

 helium as unity in each case. 



He adds that, in order to obtain the absolute values of the 

 radii, each number in the third column must be multiplied 

 by 1*68 x 10 8 . The number of molecules per unit volume 



* Communicated by the Author. 



f " The Molecular and some other Constants of the Inactive Gases/' 

 by G. Rudorf, Ph.D., B.Sc. Phil. Mag. June 1909, p. 795. 



X " On the Viscosities of the Gases of the Argon Group," by A. O. 

 Rankine, B.Sc. Proc. Roy. Soc. vol. lxxxiii. p. 516 (1910). 



" On the Variation with Temperature of the Viscosities of the Gases of 

 the Argon Group," by A. O. Rankine, B.Sc. Proc. Roy. Soc. vol. lxxxiv. 

 p. 181 (1910). 



"On the Refraction and Dispersion of Argon and Redeterminations of 

 the Dispersion of Helium, Neon, Krypton and Xenon,'' by & M. Cuth 

 bertson. Proc. Roy. Soc. vol. lxxxiv. p. 13 (1910), 



