some other Constants of the Inactive Gases. 



799 



Of course this method o£ calculating a is only applicable to 

 helium and argon, as L is not known for the other gases. 



Jeans (J. c. p. 250) by introducing a number of corrections 

 for the persistence of velocities after collision, &c, deduced 

 the formula 



L = 



1-31 



This would give 



o- = 1*58^/2 VI 



(B) 



(a) Upper limit of a from the density of the liquid or 

 solid. 



It is assumed that in the liquid or solid state, the mole- 

 cules are so closely packed together that the volume they 

 inhabit is practically the volume they themselves occupy. 

 This method was first used by Loschmidt. In this case V 

 will be simply the ratio of the density of the gas to the 

 density of the liquid. For helium, Kamerlingh Onnes 

 (Communications from the Phys. Labor. Leiden, Nr. 108 

 (1908), and Nature, lxxviii. p. 370 (1908)) found the density 

 of the liquid (d) to be 0*15. For argon the highest value 

 recorded by Baly and Donnan (J. C. S. lxxxi. p. 907 (1902)) 

 is 1*123. From these values we get the following for a: — 





P- 



d. 



Y^ p . L. 

 d 



<T. 



Helium ... 

 Argon 



00001769 

 0-001782 



015 

 1123 



1-18x10— 3 285x10-5 cm. 



l-252xl0~ 3 .l-006xl0-°cm. 



1 



28-5x10-8 cm. 

 10 7X10- 8 cm. 



(b) From the coefficient b of van der Waals' equation. 



The coefficient h is theoretically four times the volume 

 occupied by the molecules. For helium, Kamerlingh Onnes 

 (I. c.) found />= 0*0007. For argon we can calculate b 

 from the critical constants {vide the corresponding section 

 infra), and find £ = 0*001317. 





b. 



-1- 



L. 



a. 



Helium 



Argon 



0-0007 

 0-001347 



0-00018 

 0-000337 



2-85xl0 _5 cm. 

 1-006 Xl0- 5 cm, 



4-35xl0~ 8 cm. 

 287 Xl0~ cm. 



