HETEROGENEOUS EQUILIBRIA 261 



cylic acid is considerably greater. It appears, therefore, that, on the 

 addition of an electrolyte, so far as the solubility relations are concerned, 

 substances with polar molecules are affected in the same way as are those 

 with non-polar molecules. With polar substances, the same specific 

 effects are found which are characteristic of non-polar substances. At 

 high concentrations of the added acid, the specific nature of the effects 

 indicates some manner of interaction between the two acids. 



b. The Solubility of Strong Binary Electrolytes in the Presence of 

 Other Strong Electrolytes. The solubility of a strong electrolyte is, in 

 general, depressed on the addition of another strong electrolyte having a 

 common ion. On the addition of a salt without a common ion, the 

 solubility is in general increased, presumably owing to the formation of 

 un-ionized molecules as a consequence of a metathetic reaction. The 

 relations are much simpler with binary electrolytes than with electrolytes 

 of higher type. The solubility relations are also greatly affected by the 

 concentration of the electrolyte, whose solubility is under consideration. 



In Table CIII are given values for the solubility of thallous chloride 

 in water at 25 in the presence of various electrolytes. 23 The results are 



TABLE CIII. 



SOLUBILITY OF THALLOUS CHLORIDE IN THE PRESENCE OP OTHER 



ELECTROLYTES. 



Cone, of 

 added salt HC1 KC1 BaCl 2 T1N0 3 T1 2 S0 4 KNO a 



shown graphically in Figure 51. An examination of the table and the 

 figure shows that the solubility change in the case of different electro- 

 lytes is of the same order of magnitude for salts of the same type. The 

 depression due to the addition of hydrochloric acid is slightly greater 

 than that due to potassium chloride or thallous nitrate. Ternary salts, 

 having an ion in common with thallous chloride, cause a depression which 

 is very nearly the same as that of binary salts. The solubility is 

 markedly increased due to the addition of salts without a common ion. 

 While the solubilities due to the addition of different salts differ, this 



"Bray and Winninghoff, J. Am. Chem. 8oc. S3, 1671 (1911). 



