374 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



ions of salts in ammonia solution, as we have seen, do not differ greatly. 

 This indicates that the negative carrier in the metal solutions is of rela- 

 tively small dimensions. ' Nevertheless, if the negative carrier in these 

 solutions were the negative electron unassociated with matter, we should 

 expect a much greater value. It is known, however, that, owing to elec- 

 trostatic action, a charge placed in a fluid medium tends to condense 

 about it an atmosphere of the surrounding molecules. In gases at higher 

 pressures, the speed of the negative carrier is as low as, and often lower 



300 



sso 



200 



too 



SO 



o.o 



o.s 



t.s 



Log F. 



2.0 



3.0 



FIG. 64. Relative Speed of the Negative and Positive Ions of Sodium in Liquid 

 Ammonia at Different Concentrations. 



than, that of the positive carrier and it is only at low pressures that the 

 negative carrier in gases loses its envelope of surrounding molecules 

 and acquires a high speed. It is not surprising, therefore, that the nega- 

 tive electron in liquid ammonia should possess a speed comparable with 

 that of ordinary ions. At higher concentrations, however, as is indicated 

 by the increased carrying capacity of the negative ion, the size of the 

 surrounding envelope evidently diminishes and, indeed, it has been shown 

 that some of the negative carriers are completely unassociated with 

 ammonia. 



If the negative carriers are associated with ammonia, then obviously, 



