some other Constants of the Inactive Gases. 801 



Summary. 

 The following table summarises the results obtained in this 



section. 



Values of a from the relation cr^G^^VL. 





v =§- 



4 



K+2' 



A* 2 +2 



Helium ... 

 Argon 



28-5xl0~ 8 cm. 

 10-7xl0~ 8 cm. 



4-35xl0~ 8 cm. 

 2-87xlCT s cm. 



0-597 Xl0- 8 cm. 



0-559 x 10 _8 cm. 

 l-59xl0 -8 cm. 





Using Jeans 5 formula, these values must be reduced in the 

 ratio 6 : 4*58, and this will give the following values for a. 



Values of a from the relation o- = 4*58 V2VL. 





T =5- 



y- h y_K-1 



4' K + 2" 





Helium ... 

 Argon 



21-8xl0- 8 cm. 

 8-16x10 ~ 8 cm. 



3-32 X 10~ 8 cm. 0-455 X 10 _8 cm. 

 219xl0 -8 cm.' 



0-426 Xl0- 8 cm. 

 l-21xl0- 8 cm. 



i 



2. Hie method involving X. 



In the former section we put 



7T 



V: and conse- 



quently if we know N, the number of the molecules in unit gas 

 volume under normal conditions of temperature and pressure, 

 we can obtain another series of values of a independently of 

 the mean free path L. 



The most accurate values of N, which, if Avogadrd's law 

 be true, is not dependent on the nature of the gas, are those 

 obtained by methods which have no reference to the kinetic 

 theory. From determinations of the charge on an ion, 

 Thomson deduced the value N=3'6 x 10 19 per 1 c.c, and 

 Wilson N = 3xl0 19 to GxlO 19 . From his electromagnetic 

 theory of radiation, Planck (Ann. d. Phjs. iv. p. 5G4 (1901) 

 and Arch. JSeerl. (ii.) vi. p. 55 (1901)) deduced the value * 



* Nernst {Tkeoretische Chenue. 5te A.ufl. p. 430) gives Planck's value as 

 5 X 10 10 , but I do not know where he has got it from. The reference 

 given is to another paper. It might be pointed out that Sirk (Ann. d. 

 Fhys. xxv. p. 894 (1908)) has obviously copied this figure and the wrong 

 reference, without first verifying either— always a risky proceeding. 

 — G.B, 



