90 



CONDUCTIVITY AND VISCOSITY OF SOLUTIONS 



and have a maximum at about the 30 per cent alcohol mixture. The 

 values for the solvent are slightly higher than those for the solution. 



Sodium iodide, like potassium iodide, increases the viscosity of mix- 

 tures containing a higher percentage of alcohol. At 15 the transition- 

 point occurs in the neighborhood of the 50 per cent mixture. At 25 

 and 35 somewhat irregular results were noted. The salt increases 

 the viscosity of all the solvents through the 50 per cent mixture. 

 Beyond that point an apparently periodic effect occurs, negative vis- 

 cosity appearing only in the 40 per cent and 20 per cent mixtures. 

 Reference to the tables will show that the difference between solution 



100 

 95 



90 

 &5 

 80 

 75 

 70 



65 



j5 



E 60 

 55 

 50 

 45 

 40 

 35 

 30 

 25 



150 

 E 

 45 



40 

 35 

 30 

 25 



10 20 30 40 50 60 70 80 90 100 o 10 20 30 40 50 60 70 80 90 100 



Percentage alcohol. x = solvent. o=solution. 

 FIG. 35. Fluidity of KI at 15 and 25. 



Percentage alcohol. x=solvent. o=solution. 

 FIG. 36. Fluidity of Nal at 15. 



and solvent is very small for the N/8 concentration. In the 10 per 

 cent and 5 per cent mixtures the salt exerts scarcely any effect on the 

 solvent at 25 and 35. 



From this it would seem that the molecular volume of the dissolved 

 sodium iodide is smaller than either the associated alcohol or water com- 

 plexes ; but in mixtures of these two solvents in which the association 

 becomes smaller, a negative viscosity effect is apparent as soon as the 

 dissolved particles are larger than the ultimate particles of the solvent. 

 From the data at hand the change in association appears to take place 

 more largely in the case of the water than of the alcohol. Similar 

 reasoning holds for potassium iodide. 



The explanation of the phenomenon of negative viscosity as first 

 offered by Veazey 1 , has been further elaborated by subsequent in- 



. Chem. Journ., 37, 405 (1907) 



