254 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



For lithium carbonate, silver sulphate, potassium bromate, and potas- 

 sium perchlorate, there is a rough parallelism in the order of the solu- 

 bility effects among the different electrolytes in the presence of a non- 

 electrolyte, although numerous exceptions occur, particularly in the case 

 of lithium carbonate. So, also, the solubility effect in general decreases 

 in the order lithium carbonate, silver sulphate, potassium bromate, potas- 

 sium perchlorate, although here, again, exceptions are found. There can 

 be no question, however, that a parallelism exists between the solubility 

 effects for different salts and for different electrolytes. Roughly, those 

 non-electrolytes which suffer the greatest solubility change on the addi- 

 tion of a non-electrolyte cause the greatest change in the solubility of a 

 given electrolyte, and those electrolytes which cause the greatest change 

 in the solubility of a given non-electrolyte suffer the greatest solubility 

 change on the addition of a given non-electrolyte. These relations, how- 

 ever, are only roughly true. It is again evident that the effect of different 

 non-electrolytes on the solubility of electrolytes is primarily a function 

 of the nature of the electrolyte and of the added non-electrolyte. Similar 

 measurements on the solubility effects in non-aqueous solvents do not 

 exist. 



5. Solubility of Electrolytes in the Presence of Other Electrolytes. 

 If an electrolyte is added to a solution of another electrolyte, which is 

 present as a solid phase in equilibrium with its solution, the solubility 

 effect will obviously depend upon the interaction between the two elec- 

 trolytes. Since electrolytes in solution are ionized and equilibrium estab- 

 lishes itself almost instantaneously, it is to be expected that various 

 effects will be observed. We have to consider here two cases which are 

 of practical importance : First, the solubility of an electrolyte in the pres- 

 ence of another electrolyte with a common ion; and, second, the solubility 

 of an electrolyte in the presence of another electrolyte without a com- 

 mon ion. 



a. Solubility of Weak Electrolytes in the Presence of Strong Electro- 

 lytes with an Ion in Common. If the law of mass-action is applicable, 

 the addition of a binary electrolyte to a second binary electrolyte having 

 an ion in common should cause a depression in the solubility of the second 

 electrolyte. We have the equations: 



M: x x,- 



~~ 



