m 



Salt 



Temperature- 

 coefficient 



Temperature- 

 coefficient 



between 0° and i between 0'' and 



Dilution 



5^ C 



30' C. 



X. Sodium Salicylate 



0.013 



From a consideration of' equal effect of temperature on the con- 

 ductivity and fluidity of acjueous electrolytic solutions of pure water, 

 KoHLRAUSCH ') presents the hypothesis that, round every ion, and 

 moving along with it, there is an atmosphere of the solvent whose 

 dimension is determined by the individual characteristics of the ion; 

 and the electi-olytic resistance of an ion is a frictional resistance 

 which increases with the extension of the atmosphere, the direct 

 action between the ion and the outer portion of the solvent dimin- 

 ishing as the atmosphere becomes of greater thickness. This hypo- 

 thesis is in agreement with the fact that the most sluggish ions 

 have the temperature coefficient of resistance very like the tempe- 

 rature coefficient of viscosity of the solvent. The hypothesis is in 

 further agreement with the circumstance that the temperature formula 

 for the mobility of the ions shows in all cases a convergence towards 

 the zero value between — 35° C and — 41° C, the zero value of 

 the fluidity of water being reached at — 34° C. 



From our work it is evitient that the same hypothesis may be 

 applied e(iually in alcoholic solutions. Tlie electrolyte binds with 

 it a few molecules of the solvent, the alcohol, wliicli forms an 

 atmosphere round it, and it moves through the solution with this 

 alcoholic atmosphere surrounding it. The frictional resistance it meets, 

 is not the frictional resistance between the ions and the solvent 

 alcohol, but it is the frictional resistance of the alcoholic atmosphere 

 round tiie ions against the solvent molecules. 



Chemical Laboratori/, Presidency College, Calcutta. 

 "~^Pr^c. Roy. Soc. 1903, 71, 338. 



