314 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



cases. The number of examples of this type might be greatly multiplied. 

 Liquid ammonia is the only non-aqueous solvent in which electrolytic 

 reactions have been extensively studied so that this discussion must be 

 largely confined to solutions in this solvent. The study of reactions in 

 ammonia have led to a considerable extension of our notions respecting 

 electrolytic reactions in general, and have greatly advanced our knowl- 

 edge regarding the nature of various nitrogen compounds. Solutions in 

 ammonia exhibit properties similar to those of solutions in water, be- 

 cause of the similarity of constitution of the two solvents. In water we 

 have the ionization reaction: 



H 2 = H + + OH- 



and in ammonia the corresponding reaction: 



NH 3 = H + + NH 2 -. 



The negative ions in ammonia and water differ, but exhibit many points 

 of similarity. The positive ions in the two solvents are the same and 

 exhibit a similar behavior. In ammonia solutions, however, the hydrogen 

 ion appears to be identical with the ammonium ion, whereas in aqueous 

 solution the hydrogen ion is in all likelihood a complex between hydro- 

 gen and water, so that the two ions are not identical. The same is doubt- 

 less true of most ions. In their essential behavior, however, the hydrogen 

 ions in ammonia do not differ materially from the hydrogen ions in 

 water. One of the characteristic properties of the hydrogen ions is its 

 tendency to react with metals to form a salt and hydrogen. In water, 

 for example, we have the reaction: 



Mg + 2HC1 = MgCl 2 + H 2 . 

 So, in ammonia we have the reaction: 



Mg + 2NH.C1 = MgCl 2 + H 2 + 2NH 3 . 



In this last reaction, the ammonia resulting from the reaction is identical 

 with the solvent molecules and therefore may be omitted from the reac- 

 tion equations. In aqueous solutions of the acids this is always done, 

 for it is less evident that water is concerned in the reaction. In am- 

 monia, the acids react with bases to form salts and water, corresponding 

 to the reactions in aqueous solutions; thus: 



(CH 3 ) 4 NOH + HC1 = (CH 3 ) 4 NC1 + H 2 O in water, 

 and (CH 3 ) 4 NOH + NH 4 C1= (CH 3 ) 4 NC1 + NH 3 + H 2 in ammonia. 



