Viscosity and Atomic Weight for the Inert Gases. 51 



previous paper for purposes of comparison, helium in all 

 cases being taken as unity. 



The Inst three columns refer to the molecular dimensions 

 corrected according to Sutherland's theory. This is that 

 owing to the increased frequency of collision caused by 

 molecular attractions, the molecules behave as though their 

 dimensions were greater than their re d values. It we wish 

 to find the true radius we must diminish that calculated by 



the simple theory in the proportion l:il-fm). Tha 



numbers in the last three columns are obtained from columns 

 3 to 5 by the application of this process. 



Table III. 





With Si 



itherland correction. 



Gas. 



Relative 

 Atomic wt. 



Molecular 

 Radius. 



Molecular 

 Volume. 



Density 

 of the atom. 



Molecular 

 Radius. 



Molecular 

 Volume. 



Density 

 of the atom. 



He... 



1-00 



1-00 



1-00 



1-00 



1-00 



1-00 



1-00 



Ne ... 



5-06 



119 



1-69 



2*99 



1-21 



1-79 



2-83 



A ... 



10-08 



1-68 



4-74 



212 



T53 



3-59 



2-81 



Kr ... 



20 96" 



1-91 



6-98 



300 



1-65 



4'53 



4-63 



X ... 



33 01 



2-25 



11-37 



290 



1-83 



6-11 



5-40 



Em- 



55*5 



2-57 



16'97 



328 



1'93 



716 



775 



Finally, using the value N = 2*8 x 10 19 for the number of 

 atoms per c.c. at N.T.P., we obtain for the absolute molecular 

 radius of radium emanation 



s Em = 2'16 x 10" 8 cm. 



This is the uncorrected value, L e. the value obtained 

 without applying- the Sutherland diminution, it being still 

 customary to record molecular dimensions in this way. 



In order to avoid confusion with regard to these two 

 separate measures of the molecular radius, the following- 

 consideration may be found useful. 



Rayieigh * has pointed out that if the molecules mutually 

 attract one another, mutual repulsions must also exist, and 

 that the laws of variation of force with distance are different 



* Pliil. Mag. xxx. pp. 285 & 456 (1890). 

 E 2 



