70 Mr. Clive Cuthbertson on New Determinations of 



Table I. 



Element. 



1. 



Relative 

 viscosity. 



2. 



Relative 



mean free 



path. 



3. 



Relative 



molecular 



radius. 



4. 



Absolute 



molecular 



radius) 



xio 8 . 



5, 



Absolute 



molecular 



volume 



per normal 



unit vol. 



6. 



2 



(,"00-1)3- 



7. 



Ratio of 

 column 5 



to 

 column 6. 



Helium 



Neon 



1-000 

 1-585 

 1-124 

 1-253 

 1-136 



1000 

 0-704 

 0-354 

 0-274 

 0198 



1-000 

 119 



1-68 

 1-91 

 225 



•84 



•9996 

 1-4112 

 1-6044 

 1-890 



•0000695 

 •0001171 

 •0003296 

 •0004844 

 •0007918 



•0000231 

 •0000444 

 •0001848 

 •0002791 

 •0004545 



30 



2-53 



1785 



1-733 



1*742 



Argon ...... 



Krypton . . . 

 Xenon 







is taken as 2'8 x 10 19 . The calculation is based on the 

 relation 



L~ =\/"2 . N7ra 2 , 



where L is the mean free path and a is taken to be the 

 molecular radius. It is, however, more usual to take a as 

 the radius of the sphere of action of the molecule and equal 

 to the molecular diameter. Hence the absolute value of the 

 molecular radius is given by multiplying Rankine's figures by 



1-68 xlO 8 

 2 



The sum of the volumes of the molecules per unit volume 

 of aas is 



N 



^47T<7 3 



These figures are given in the fourth and fifth columns of 

 the table. 



Turning now to the refractivities, we start from Clausius's 

 well-known equation 



k-1 



where g denotes the fraction of the volume containing a gas 

 which its molecules actually occupy. This becomes 



pr + 2 



F 



