136 



CONDUCTIVITY AND VISCOSITY 



Returning to the fundamental point; why do these rubidium and 

 ammonium salts cause conductivity minima and also fluidity minima 

 in some of these ternary solvents and not in others? In some cases, 

 a flat curve or a straight line is produced. In all such cases the fluidity 

 coefficients are negative. These negative coefficients occur only with 

 the solvents containing 40 and 50 per cent acetone. The first sug- 

 gestion would be that it was due to some specific effect of acetone on 

 the fluidities of these solvents, but a study of them and also of figure 

 58 renders this view open to question. The explanation suggested is 

 the polymerizing action of acetone. The normal action of these salts 

 is to produce positive fluidity coefficients on account of large molecular 

 volumes. The formation of a polymer would reduce the number of 



50 



45 



a 35 



30 



20 



35 



25 



25- 



10 



Volume concentration 



60 



= conductivity curves. 



- = fluidity curves. 



FIG. 55. Conductivity and fluidity of rubidium bromide in the 1-2-1 solvent at 



15, 25, and 35. 



molecules and hence diminish or overcome the action that results in 

 these positive coefficients. Jones and Mahin 1 have shown that cad- 

 mium iodide, lithium nitrate, and lithium acetate polymerize in acetone. 

 More data on the polymerization of inorganic salts is desirable. 



Figure 57 show's for comparison the temperature coefficients of con- 

 ductivity and fluidity for an N/10 solution of ammonium iodide in the 

 ternary solvents at 15 to 25 and 25 to 35. There is a striking 

 similarity between the curves for the conductivity and fluidity coef- 

 ficients. 2 They are lower for the higher range in temperature, as 



'Carnegie Inst. Wash. Pub. No. 180. 



2 The unusual feature shown by curve II for the 2-2-1 solvent is probably due to this solvent 

 containing 40 per cent of acetone, a very volatile liquid. This solvent also contains only 20 per 

 cent of water, which is the minimum amount necessary to cause these three liquids to form a 

 homogeneous mixture. 



