353 



Columm I contains ihe absolute temperature T, column II the 

 conductivity found A''; column IIT the values computed by means 

 of Sutherland's formula. The value of C in this formula, 57.5 for 

 neon, veas derived from the first two measurements '). 



It appears, therefore, that Sutherland's formula cannot represent 

 the dependence on the temperature of the conductivity for neon at 

 the lower temperatures. Tliat Sutherland's formula is not satisfactory 

 at low temperatures, was proved before t)y investigations on the 



1) In connection with the value of C and the high viscosity of neon /;„ = 2981 . 10-7, 

 it is of interest to calculate the diameter t of the neon-molecule. Using Chapman's 

 formula (London Phil. Trans. A. Vol. 216, 1916, p. 279) 



7j = 0.491(1 +6,) "'^ 



\/1.nö\n(\^-\ 



where the small correction ê« is determined by C, we find, witli u = 2.77 . 10", 

 0- ^ 2.32 ■ 10-s . 



An approximate value of o- may also be obtained by means of the critical 

 constants. From van der Waals's formulae in the notation of H. Kamerlingh 

 Onnes and W. H Keesom : Die Zustandsgleicliung, Comm. Supplem. N". 23, 

 Fussn. 284 it follows, using 



Pk — K^ 



that : 



^1 ■ Pk 



ir 



According to van der Waals (see Fussn. 459 I.e..) -j^ is approximately equal 



^1 - 

 to the theoretical value Vs- hence: 



R Tjc 



8 Pk 



Using iV = 62.10'2 and by means of the critical constants /)^. = 26.86 (intern. 

 atm.) and Tj. = 44°.75 K. (H. Kamerlingh Onnes, G. A. Urommelin and P. G. Gath : 

 Coram. NO. 1516) we find ^ = 2.36.10-8 . 



If we use the isothermals for neon at 0^ and 20° G. (H. Kamerlingh Onnes 

 and C. A. Crommelin Comm. N". 147d) and assume, tliat (a in van der Waals's 

 equation of state is independent of the temperature, one finds (comp. H. Kamerlingh 

 Onnes, Comm. N». 102a p. 5) 



6,, = -12 '- = 0-001398. 



20 R 



From the value of the virial-coefficient Ca at 0° C. one obtains 



b,„=^ 7, ^,= 0-00136 

 Using the former of the two values the result is cr = 2.90 . 10—8. 



