196 SCIENCE PROGRESS 



The theory of Ghosh is based on the following postulates : 

 (i) complete ionisation of the electrolyte ; (2) arrangement of 

 the charged particles in a space-lattice in the solution ; (3) the 

 oppositely charged ions can form saturated electrical doublets 

 and the work required to separate them is the electrical work 

 done in separating two charged particles ; (4) an ion is free to 

 conduct the current only if its kinetic energy is greater than 

 half the work required to separate it from its partner ; and (5) 

 the distribution of velocities is according to the Maxwell law. 

 For binary electrolytes he deduces a relationship for a, the 

 degree of ionisation as defined by conductivity measurements, 



,RT In i = ^° '' VI^ ° 

 a D I V 



V 



where D = dielectric constant of the solvent. 



Criticism is directed, in the first place, against the choice 

 of experimental data, the methods of calculation, and the 

 narrow range of concentration over which comparisons were 

 made between theory and experiment. Incorrect values were 

 used by Ghosh for //^, the dielectric constant of water, 

 the degrees of polymerisation and ionisation in non-aqueous 

 solvents, etc. When the corrected values are introduced into 

 his equations, relatively large deviations are observable 

 between theory and experiment. Thus Arrhenius shows that 

 in ethyl alcoholic solutions the discrepancy is particularly 

 marked. For ri KI the calculated value for a is 31*4, whereas 

 the observed value is 22*4. 



In the second place, it is urged that the postulates are 

 inconsistent among themselves, and that the equations which 

 Ghosh employs do not follow from his postulates. It is also 

 doubtful if the Maxwell law of distribution can be applied to a 

 system of charged ions. Kendall shows that the electrical 

 work necessary to disperse 2N particles of a dissolved salt 

 will he A = 175 NE'jDr instead of NE^/Dr as assumed by 

 Ghosh. Also Chapman and George point out that the expres- 

 sion used for the distribution of velocities is erroneous. When 

 both of these corrections are made, the disagreement between 

 theory and experiment is seen to be far beyond the limits of 

 experimental error. 



The theory of Ghosh requires that all electrolytes of the 

 same type should be equally ionised. Partington shows that 

 considerable divergences exist between the experimental 



values of — for different electrolytes in aqueous solution. The 



r'oa 



divergences are still more marked in solutions of non-electro- 

 lytes. Ghosh gets over this difficulty by a new method of 



