ioi DIFFUSION OF GASES 271 



on diffusion, that the exponent has different values for dif- 

 ferent gases, and his observations give for 



Air -carbonic acid . . . . n = 0-968 

 Hydrogen oxygen . . . 0'755 



Carbonic acid nitrous oxide . . 1-050 



Carbonic acid hydrogen . . 0'742 



Oxygen nitrogen .... 0-792 



and these values so far agree with those which the same 

 observer l obtained for the dependence of the coefficient of 

 viscosity on the temperature, viz. 



Air n = 0'76 



Hydrogen .... 0-70 



Oxygen . . . . 0-80 



Nitrogen .... 0-74 



Nitrous oxide . . . 0-93 



Carbonic acid . . . 0*98 



that the exponent for the diffusion in the case of any pair 

 lies, with one exception, between the exponents for the 

 viscosity of the two gases concerned. 



From these experiments we cannot doubt that the 

 variability of the two phenomena, viscosity and diffusion, 

 with the temperature is to be referred to exactly the same 

 causes. Both coefficients, that of viscosity and that of 

 diffusion, depend on the temperature, not only because 

 their formulae contain the molecular speed H, but also in 

 so far as the radii s and a of the spheres of action are 

 variable with the temperature. The only difference in 

 their variability with the temperature consists in that for 

 diffusion being greater than that for viscosity in the ratio 

 of 1 + o3 to 1. 



We may further conclude that the change of both 

 magnitudes s and a- with the temperature is effected by 

 forces that are equal or, at least, of like kind. Both magni- 

 tudes are radii of spheres, of action ; * refers to the mutual 



1 Wien. Sitzungsber. 1876, Ixxiii. Abth. 2, p. 433; Carl's Bepert. 1877, 

 xiii. p. 130. Compare 85. 



