112 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



also found in glycerine. In general, however, the negative viscosity 

 effect appears only in the case of solutions in solvents having high dielec- 

 tric constants. As a rule, only those salts which show relatively a slight 

 tendency to form stable hydrates exhibit a negative viscosity effect in 

 solution. In Table XLI are given examples of the relative viscosities of 

 solutions in ammonia, 5 water, and methylamine 5 at a number of con- 

 centrations. 



TABLE XLI. 



COMPARISON OF THE VISCOSITY CHANGE DUE TO ELECTROLYTES IN 

 DIFFERENT SOLVENTS. 



Solvent Solute Relative Viscosity at Concentration: 



0.5 1.0 2.5 



Water LiCl 1.05 1.10 1.42 



Ammonia KI 1.16 1.38 2.38 



Methylamine .... AgN0 3 1.40 1.96 6.38 



It will be observed that in a 0.5 normal solution the viscosity increase 

 for potassium iodide in ammonia is approximately three times that of 

 lithium chloride dissolved in water, while the viscosity change for silver 

 nitrate in methylamine at the same concentration is approximately three 

 times that of potassium iodide in ammonia. Approximately the same 

 ratio of increase holds at somewhat higher concentrations. In this con- 

 nection it should be noted that the viscosity effect in the case of lithium 

 chloride is relatively very great compared with that of other salts in 

 water. In the case of potassium iodide the viscosity effect is actually 

 negative in water. We see, therefore, that the lower the dielectric con- 

 stant of the solvent, the greater is the increase in viscosity due to the 

 added electrolyte. The dielectric constants are approximately 80, 22 

 and 10 for water, ammonia, and methylamine respectively. There are 

 no data available relative to the viscosity of solutions in the higher 

 amines, but qualitative data indicate that the viscosity effect increases 

 very greatly with increasing complexity of the solvent, or, rather, with 

 decreasing dielectric constant of the solvent. It is evident that there is 

 a relation between the magnitude of the viscosity effect due to an elec- 

 trolyte and the dielectric constant of the solvent in which this electrolyte 

 is dissolved. 



In Figure 16 are shown curves 6 representing the relation be- 

 tween the viscosity and the concentration of aqueous solutions of 



8 Fitzgerald, loc. cit. 



Sprung, Pogg. Ann. d. Phys. 159, 1 (1876). 



