806 Dr. R. D. Kleeman on the Nature of the 



length of path in different gases are not proportional to the 

 corresponding expenditures of energy, The writer* has 

 calculated the total energy expended by the a particle on an 

 ion made from different atoms, and found that some of the 

 energies differ from one another by as much as 40 per cent. 

 It appears very probable, therefore, that the above explana- 

 tion is the true explanation of the law found by experiment. 

 The chemical attraction close to a molecule thus seems to 

 be inversely as the third power of its distance from the 

 centre of the molecule, whiph gradually becomes the inverse 

 fifth power as the distance approaches that of separation of 

 the molecules in a liquid, and for distances much greater 

 than this we have seen that the power of the distance must 

 be greater than the fifth, otherwise the attraction will be 

 greater than the gravitational at distances lor which we 

 knpw this is not the case. 



Diffusion of Gases. 

 Assuming that the attraction between two molecules is 

 — - , that is inversely as the fifth power of their distance of 



£0 



separation, Maxwell has obtained a formula fpr the coefficient 

 of diffusion of a gas 1 into a gas 2 which gives 



J) -Pi 1 I 



B ) 1/2 p» 



^ 2 \m 1 m 2 (rni + m 2 ) j 



where p^ p 2 , pi, P25 are the partial pressures and densities of 

 the gases, and p^Pi^-p2- The value oi B according to the 

 investigation in this paper is K 2 ^% . % Vm 2 . Let us 

 consider the case when the number of molecules 1 is sjnaU 

 in comparison with the number of molecules 2, so that 

 p^p 2 . We have 



Pi PT , p 2 m 2 



and t}ie equation may therefore be written 

 RT 2 1 



D = 



p 2 2 m im2 A j KX Vm! . S W - 





?n 1 m 2 (w 1 -f m 2 ) 

 f Prop. Eoy. Soc. A. vol, lxxix. p, 220 (1907), 



= M f ^ + ^3 y/ 2 



