1166 



has to multiplied, instead of by the factor V,, by the mass-ratio 

 or — respectively. A rigorous treatment of the problem 



is impossible, but it would seem tliat an approximately correct result 

 will be obtained, if in the above formulae for ƒ the tirst term in the 

 denominator which refers to collisions between like molecules is given 

 the factor V,, and the second term which depends on the unlike 

 collisions is multiplied by the aforesaid mass-ratio. In this manner 

 the persistence-factors ƒ which apply in the case of viscosity assume 

 the following foi*m 



,■■ -1 :Sl- i ^/2 r,,.^,,'( 1 + „^ V. X 0.40C - 



f 1 + ^V 



r,= l:|l- 4 l/2.,^.;(l + ^)^« X Ö-^Öö- 



»Wi+wiW'. , C,,\ m, — 0.\88m, 



rn. 





m„ — 0.188m, 



m^\m^ V m, V 273y vi^\m^ \ 



while the viscosity of the mixture is given by the formula 



7i = 0.35 '- d^u.l, f\ + 35 '^ d,uJ.J\ . 

 n ' ti 



For CO^ and H^ with n,—n,='/,n calculation gives rj=0:0001482. 



The theory therefore actually gives a maximum in the viscosity, 

 in accordance with observation which had not been explained hitherto. 

 The observed maximum lies at 707„ CO, and is not quite so high viz. 

 about 0.000144, but a nearer agreement could not really be expected. 



For argon and helium calculation gives 



for the mixture 3:2 i] = 0.0002294 

 1:1 ti = 0.0002321 . 



Observation gives a maximum near the first named mixture with 

 7^ = 0.0002207 ; in this case the theory gives again too high a value. 

 Whereas therefore a numerical agreement is absent, we may conclude 

 from the investigation that the ordinary gas theory which treats the 

 molecules as mutually attracting elastic spheres can without being 

 strained explai]» the occurrence of a maximum in the viscosity of 

 the above mixtures. 



