101 DIFFUSION OF GASES 269 



into that which would hold if the mutual collisions of 

 particles of the same kind might be left out of account. 

 We need not therefore pursue this improbable assumption, 

 according to which the coefficient of diffusion would have 

 the constant value 



D = 

 " 



/( 

 V V 



any further here, if we obtain an answer to our question 

 from the more general formula. 



Since the magnitudes denoted by 7 do not depend on the 

 pressure p, the equations show directly that according to the 

 theory the coefficient of diffusion is inversely proportional to 

 the total pressure of the two diffusing gases. But this is 

 the very law which Loschmidt deduced in 1870 from his 

 observations, and which has been confirmed by all later ex- 

 perimenters. 



Loschmidt has further concluded from his observations 

 that the coefficient of diffusion increases as the temperature 

 rises, and that it increases indeed proportionally to the 

 square of the absolute temperature. The theoretical formula 

 likewise requires an increase of the coefficient with rise of 

 temperature. In the formula p is not variable when we are 

 dealing with experiments that are made at constant tem- 

 perature and pressure. If the magnitudes 7 were also 

 independent of the temperature, D would increase propor- 

 tionally to the f power of the absolute temperature (since 

 this on the kinetic theory is proportional to II 2 ), and there- 

 fore less than is really the case according to Loschmidt's 

 experiments. 



But according to the observations on viscosity the radii 

 ?! and s- 2 of the spheres of action are dependent on the 

 temperature, either actually or apparently ; this is also pos- 

 sible, and, indeed, highly probable, for the newly-introduced 

 magnitude a-, which has a similar meaning. If we may 

 assume that <r and the magnitudes s are variable, at least 

 approximately, in the same way with the temperature, the 

 coefficient of diffusion D must increase with the temperature, 

 according to the same law as the product of the coefficient 



