112 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



The conductivity of the pure acetone used in these experiments was 

 1.516 x 10- 6 ; that of the pure alcohol, 0.857 X KT 6 . 



These results show that complete dissociation is nearly reached only in 

 the pure alcohol, and that the mixture is dissociated about as we might 

 expect from the law of averages. We note that the maximum is very pro- 

 nounced. 



The conclusion of Dutoit and Friderich and of Jones and Carroll, that 

 conductivity is inversely proportional to viscosity, and directly propor- 

 tional to the association factor of the solvent (or to the amount of dissocia- 

 tion), is incomplete. It fails to take into consideration changes in the 

 dimensions of the ionic spheres. 



In the conductivities of lithium nitrate, in mixtures of acetone and water, 

 the decreased fluidity manifests itself again. We notice, however, that the 

 power of the acetone to produce smaller (or more symmetrical) ionic spheres 

 is not destroyed by substituting water for methyl alcohol or ethyl alcohol. 

 Practically all of the dilutions in the 75 per cent mixture of acetone and 

 water, show a decided elevation of the conductivity curves above those we 

 should expect from similar measurements with potassium iodide. That 

 increase in dissociation would make itself manifest in this way is doubtful, 

 and our theory is thus strengthened. 



Jones and Lindsay's results with lithium nitrate, in mixtures of water and 

 methyl alcohol, do not show this effect; hence the acetone acts peculiarly in 

 this respect. However, acetone behaves exceptionally in other ways. 



At this point we should call attention to the fact that lithium forms a very 

 slowly moving ion, i. e., one with a large ionic sphere, while potassium forms 

 a comparatively rapidly moving ion, i. e., one with a small ionic sphere. The 

 anions used do not differ greatly. Calcium forms an ion with a migration 

 velocity between that of lithium and potassium. It was thought best to 

 measure the conductivities of calcium nitrate in all of the mixtures, exactly 

 as with the other salts. 



The results show that the tendency towards a maximum in conductivity 

 in the mixtures is very marked indeed. Moreover, they show that calcium 

 nitrate is dissociated in the solvents very differently from lithium nitrate. 

 Calcium nitrate is dissociated to a large extent in water and methyl alcohol, 

 very much less in ethyl alcohol, and still less in acetone. In spite of all differ- 

 ences, we are struck by the fact that the maximum divergence still tends to 

 manifest itself in the 75 per cent mixture. Especially is this the case with 

 acetone and water. 



Let us now turn our attention to the concentrated solutions. In these 

 we find the tendency towards a maximum very small, or entirely absent. 

 If our explanation is correct, then, as the concentration of the salt increases 

 there will be less of the solvent for the formation of ionic spheres, or, in the 



