OTHER PROPERTIES. OF ELECTROLYTIC SOLUTIONS 317 



place, however, has been definitely shown. As a consequence of the 

 very low concentration of the H + and NH 2 ~ ions in ammonia, it is only 

 in the case of salts of extremely weak acids or bases that hydrolysis has 

 been observed. For example, when mercuric chloride is dissolved in 

 ammonia the following reaction occurs: 



HgCl 2 + NH 2 - + NH 8 = HgNH 2 Cl + NH 4 C1. 



In this case, the compound HgNH 2 Cl is insoluble and is precipitated. 

 Obviously, this precipitation proceeds until the concentration of NH 4 C1 

 is sufficiently great to bring the reaction to equilibrium. The addition 

 of an ammonium salt, which raises the concentration of the NH 4 + (hydro- 

 gen) ions, reverses the reaction, causing the precipitate to go into solu- 

 tion; while, on the other hand, the addition of an ammono-base, KNH 2 , 

 for example, results in an increased precipitation. In most instances, 

 however, salts dissolve in ammonia without appreciable ammonolysis. 

 This is indicated by the fact that in many cases the resulting base or 

 basic salt is practically insoluble and even a small degree of ammonolysis 

 would result in the formation of a precipitate. Since in the great ma- 

 jority of cases the salts yield clear solutions, it is obvious that am- 

 monolysis does not occur to an appreciable extent. 



A considerable number of reactions have been studied in solvents of 

 very low dielectric constants 49 such as benzene, toluene, etc. Reactions 

 in these solvents often take place readily and even instantaneously. As 

 a rule the salts dissolved are heavy metal salts of the higher organic 

 acids such as the oleates, stearates, etc. It has been claimed that solu- 

 tions of these salts are non-conductors, but the work of Cady and 

 Lichtenwalter indicates that, while -the order of conductance of solutions 

 of salts of organic acids in benzene is low compared with that of ordi- 

 nary solutions of electrolytes, nevertheless, benzene solutions conduct 

 far more readily than does the pure solvent. In the case of a.metathetic 

 reaction with hydrochloric acid, the conductance was found to rise largely 

 before precipitation, due, presumably, to the relatively greater con- 

 ductance of the more concentrated supersaturated solution. That solu- 

 tions of salts in such solvents as benzene are sufficiently ionized to exert 

 a marked influence on the conductance is not to be doubted. 



Metathetic reactions take place readily in solutions in solvents of 

 low dielectric constants such as benzene, but, apparently, these reactions 

 are not always instantaneous. 50 This result may in part be due to the 



Kahlenberg, J. Phys. Chem. 6, 1 (1902) ; Sammts, ibid., 10, 593 (1906); Gates 

 ibid., 15, 97 (1911) ; Cady and Lichtenwalter, J. Am. Chem. Soc. 55, 1434 (1913) ; Cady 

 and Baldwin, ibid.. 43, 646 (1921). 



80 Cady and Lichtenwalter, loc. cit. 



