418 



Mr. S, Russ on the Diffusion o) 

 Fijr. 2. 



do 



GU(V 



1 3 i, 



Variation of the Coefficient with Pressure* 



According to the kinetic theory of gases the coefficient 

 of diffusion is inversely proportional to the total pressure of 

 the two diffusing gases ; the product of the coefficient and 

 the pressure should therefore remain constant, 



The variation of the coefficient has been determined for 

 pressures between 76*4 cms. and 1'4 cm.; the small vessel 

 containing the segmented rod was used. The results are 

 recorded in Table III. & fig. 3. It will be seen that 

 over this range of pressure, with tho exception of 1*4 cm. 

 pressure, the product PxK is approximately constant, 

 its mean value being 9'34. It is difficult to say whether 

 the high value 10'9 at the lowest pressure indicates a devia- 

 tion from the above law as the gradient obtained is a 

 very small one, and relatively largo errors may be made in 

 estimating it. 



