1889.] Mr W. K. Shaw, On Electrolytes. 21 



November 25, 1889. 

 Mr J. W. Clark, President, in the Chair. 



The following were elected Fellows of the Society : 

 Arthur Berry, M.A., Fellow of King's College. 

 H. F. Baker, B.A, Fellow of St John's College. 

 E. W. Brown, B.A., Fellow of Christ's College. 

 C. Warburton, B.A., Christ's College. 



The President announced that the adjudicators of the Hopkins 

 Prize for the period 1880-82 have awarded the Prize to Mr R T. 

 Glazebrook, F.R.S., for his researches in Physical Optics. 



The following Communications were made to the Society : 



(1) On the relation between Viscosity and Conductivity of 

 Electrolytes. By W. N. Shaw, M.A., Emmanuel College. 



It has long been suspected that the resistance offered by an 

 electrolyte to the passage of electricity through it, depends in 

 some way upon the viscosity of the liquid. The mere fact that 

 the conduction of electricity is in reality convection by moving 

 ions suggests of itself that resistance may be the opposition 

 offered by the fluid to the motion of the ions. It is not however 

 in any way obvious that the resistance which moving ions would 

 meet with would be identical with the ordinary viscosity that has 

 to be overcome when a fluid is driven through a capillary tube ; 

 so that when G. Wiedemann, in 1856, found that there was an 

 analogy between the relative magnitudes of the numbers express- 

 ing the conductivity of certain solutions and those expressing the 

 fluidity (the reciprocal of the viscosity), the implied relation 

 between electric conductivity and fluidity was not at once accepted 

 as proved. And indeed, in its crudest form, the hypothesis that 

 conductivity is identical with fluidity, as we measure it by Cou- 

 lomb's method or Poiseuille's method, or that the two are propor- 

 tional, evidently cannot be maintained. For clearly a salt solution 

 becoming gradually more and more dilute approaches a finite 

 limit of viscosity, namely the viscosity of pure water, whereas the 

 conductivity apparently diminishes without limit. Moreover there 

 are numerous mobile liquids which do not conduct at all. Nor is 

 the mobility which is characteristic of fluids really necessary to 

 electrolytic conduction. Professor W. Kohlrausch has examined 

 the conductivity of fused salts of silver through a wide range of 

 temperature, and he finds that in the case of iodide of silver there 

 is no discontinuous change in the conductivity at the melting- 

 point, on the contrary the resistance only increases very gradually 

 after solidification takes place, remaining less than the minimum 



