ELECTROLYTIC SOLUTIONS IN VARIOUS SOLVENTS 65 



It will be observed that the ion conductances in ammonia and in 

 water do not stand in a fixed ratio. For example, for the silver ion, the 

 ion conductance in ammonia is 2.15 times that in water, whereas for 

 the lithium ion the conductance in ammonia is 3.36 times that in water. 

 Similarly, the conductance of the bromide ion in ammonia is 2.54 times 

 that itf water, while the conductance of the bromate ion is 3.11 times 

 that in water. We may naturally inquire as to what are the factors 

 upon which depends the conductance of different ions in different solvents. 



If the current is carried through a solution by the translation of 

 charged particles of molecular dimensions, then we should expect the 

 speed of these particles to be a function of the viscosity of the medium 

 through which they move. It might be assumed, for example, that the 

 conductance is proportional to the reciprocal of the viscosity, or to the 

 fluidity of the solvent. The viscosity of water at 18 is 10.63 X 10" 3 and 

 that of ammonia is 2.558 X 10' 3 at its boiling point. Consequently the 

 fluidity of ammonia is 4.15 times as great as that of water. If the con- 

 ductance of the ions were directly proportional to the fluidity of the 

 solvent, then the conductance of all ions in ammonia should be 4.15 times 

 as great as that of the same ions in water. We see, however, that while 

 the conductance of the various ions in ammonia is markedly greater 

 than that in water, nevertheless the ratio of the ion conductances in the 

 two solvents is in all cases smaller than this value. Furthermore, the 

 effect is one specific with respect to the individual ions. For example, 

 for the sodium ion, the value is 3.0, while for the lithium ion it is 3.36. 

 It is noticeable that the ratio for the ions increases in the order: am- 

 monium, potassium, sodium, lithium. In other words, in ammonia the 

 lithium ion possesses a relatively much higher conductance with respect 

 to water than does the ammonium ion. 



The same general relations hold in the case of the negative ions. The 

 conductance of the bromate ion in ammonia is 3.11 times that in water, 

 whereas that of the bromide ion is only 2.54 times that in water. On 

 the whole, the ion conductances in ammonia vary less than they do in 

 water. The extreme variation in the case of ammonia solutions is from 

 112, for the lithium ion, to 168, for the potassium ion, or a ratio of 1.5, 

 whereas in the case of aqueous solutions the extreme variation is from 

 33.3, for the lithium ion, to 65.9, for the thallous ion, or a ratio of 1.98. 

 For the negative ions in ammonia solution the extreme ratio is 1.21, 

 whereas for aqueous solutions it is 1.37. In general, however, the order 

 of ionic conductances in the two solvents is the same. With a few ex- 

 ceptions, ions which move very slowly in water also move very slowly 

 in ammonia. 



