386 Mr Mines, On the relative velocities of diffusion, etc. 



In the following table these results are compared with some 

 figures given by previous observers for the relative diffusivities of 

 potassium, sodium and lithium chlorides. 



It will be noticed that in the last two columns my numbers 

 fall within the limits of variation of those quoted above. This 

 fact I consider to justify the extension of the method to the study 

 of rubidium and caesium chlorides. In making these experiments 

 I aimed only at getting a rough comparison of the diffusion rates 

 of these substances, but I believe that the method might be used 

 to obtain values of considerable accuracy. 



It would be easy to simplify the conditions by keeping one 

 end of the cylinder of jelly in contact with a dilute salt solution 

 renewed at frequent intervals and the other end in contact with 

 distilled water. It is obvious that the method is limited to those 

 electrolytes which are not hydrolysed in solution. 



Conclusion. In dilute aqueous solution at 18° C rubidium 

 chloride diffuses slightly faster than potassium chloride and 

 caesium chloride slightly faster than rubidium chloride. 



The chlorides of the alkali metals show a rise in their rate of 

 diffusion which follows the same order as the increase in their 

 molecular weight and in the velocity of their kations. 



My f]-iend, Mr A. V. Hill, of Trinity College, has kindly indi- 

 cated a mathematical treatment of the subject in the following 

 note. 



* Beilstein, Liebig's Annalen, xcix. 1856, p. 165. 

 + Schuhmeister, Landolt-Bornstein's Tabellen, 1905. 

 X Long, Annalen der Physik u. Chemie, ix. 1880, p. 613. 

 § Oholm, Zeit. Physik. Chem. l. 1905, p. 309. 

 II J. C. Graham, ibid. p. 257. 

 II Ibid. Lix. 1907, p. 691. 



