114 



CONDUCTIVITY AND VISCOSITY OF SOLUTIONS 



elation to be driven back. This shifting of the minimum by the slight 

 solubility, however, seems to be clearly manifested only between salts 

 with great difference in solubility in acetone, as is the case with potas- 

 sium sulphocyanate and the rubidium halides. Of the four salts, rubi- 

 dium chloride, iodide, bromide, and nitrate, the solubility in acetone of 

 only the iodide is accurately known, so that these salts could not be com- 

 pared with each other for the relation between solubility and minimum 

 conductivity. 



The relative solubilities in water probably do not correspond to the 

 relative solubilities in acetone. The iodide and the nitrate are respec- 

 tively the most soluble and the least soluble in water ; but the conduc- 

 tivity minima of these two salts are the farthest from the ordinate, 

 corresponding to 100 per cent acetone (figs. 48 to 51). 







115 

 110 



100 

 90 



70 



s 



60 



60 



40 



N_ 

 1600 



TT 



N 



75 62.5 50 37.5 25 12.5 

 Percentage acetone 



FIG. 48. Conductivity of rubidium 

 iodide in acetone-water at 25. 



100 



90 



80 



-o 70 



60 



o 



50 



40 



30 



N. 

 1600 



N. 

 800 



200 



N 

 50 



10 



75 62.5 50 37.5 25 12.50 

 Percentage acetone. 



FIG. 49. Conductivity of rubidium 

 bromide in acetone-water at 25. 



It is not to be expected that the differences in solubility in water of 

 the different rubidium salts would show this relation, because in the 

 dilutions which are sufficiently great to give any minimum at all, these 

 salts are very far from their saturation in water. In the dilutions 

 greater than N/800, that is, where the dissociation approaches com- 

 pleteness, the minima in the conductivity curves are seen to be nearer 

 those of fluidity (figs. 48 and 51). 



A comparison of the percentage coefficients of fluidity given in 

 tables 34 to 38 with those of conductivity, shows that the two are 

 nearly equal, which is to be expected in the case of a non-sol vated salt. 



