THE CONDUCTANCE OF SOLUTIONS VISCOSITIES 111 



in the neighborhood of 0.3 as the ions become more complex; that is, 

 as the speed of the ions decreases. It follows that, in the case of very 

 slowly moving ions, the speed is inversely proportional to the viscosity 

 of the medium, more or less independent of the nature of the solvent 

 itself. It is interesting to compare the speed of ions due to radiations 

 with the speed of ordinary ions in different solvents. In Table XL * 

 are compared the speeds of the acetate ion in water, the lithium ion in 

 ammonia, and the positive and negative ions in hexane. In the last 

 column are given the values of the ratio of the speed of the ions to the 

 fluidity in arbitrary units. 



TABLE XL. 

 COMPARISON OF IONIC SPEEDS IN DIFFERENT SOLVENTS. 



Speed of ion 

 Solvent Ion S X 10* F S/F 



Water Acetate 3.58 95.35 3.76 



Ammonia Lithium 11.60 390.8 2.97 



Hexane Positive 6.03 312.0 1.98 



Hexane Negative 4.17 312.0 1.34 



It will be observed that both positive and negative ions in hexane move 

 decidedly slower than even the slowest moving ion in ammonia or in 

 water, taking into account the relative viscosities of the solvent media. 

 Apparently, in solvents of very low dielectric constant, the speed of the 

 ions relative to the fluidity of the solvent is smaller than it is in solvents 

 of higher dielectric constant. It may be inferred, therefore, that the 

 positive and negative carriers in hexane are associated with a con- 

 siderable number of the solvent molecules, as a result of which their 

 speed is relatively low with respect to that of the ordinary ions in water 

 and ammonia. 



2. Change of Conductance as Result of Viscosity Change Due to the 

 Electrolyte Itself. At higher concentrations the viscosity is a function 

 of the concentration of the solution, and, in most cases, increases with 

 it. In aqueous solutions there are, however, many eases in which the 

 viscosity decreases at higher concentrations, or rather, in which the vis- 

 cosity passes through a minimum, beyond which it again increases as the 

 concentration increases. The viscosity effect of the electrolyte, there- 

 fore, is a property depending on the electrolyte as well as on the solvent. 

 Solutions which exhibit a negative viscosity change with the concentra- 

 tion, that is, whose viscosity decreases with increasing concentration are 



4 raus ; J. Am. Chem. Spc. 36, 35 (1914), 



