738 



ELECTRIFICATION AND DIFFUSION OF WATER 



and this explains why the lithium salts attract water less actively 

 than the sodium salts with the same anion. 



Since the solutions of some of the salts with trivalent and tetra- 

 valent cations are acid (due to hydrolysis), it might be argued that 

 it is only the presence of free acid which makes the salts of Group B 

 behave differently from those of Group A. This assumption is dis- 

 proved by the fact that La2Cl6 and Ce2Cl6 which belong to Group B 

 are neutral salts; i.e., the hydrogen ion concentration of their solu- 

 tion has a pH of the order of that of the solution of neutral salts of 

 Group A . 



Since, however, the idea of a specific role of hydrogen and hydroxyl 

 ions is so general in the colloid literature it seemed of importance to 

 make sure that the differences we have established between the salts 



TABLE VI. 



Nature of solution. 



m/512 LasCle. 

 m/512 CeaCle. 

 m/192 MgCIs. 

 m/128 MgS04 

 m/128 KCl... 

 m/192 K2SO4. 



pH 



5.2 



5.15 



5.1 



5.05 



5.0 



5.0 



Concentration of balancing 

 cane sugar solution. 



Slightly above 3m/8 



below 3m/8 » 



Less than m/64 



m/64 



m/16 



3m/ 16 



of Groups A and B remain valid when the salts have an identical 

 hydrogen ion concentration. The pH of m/512 La2Cl6 was found to be 

 5.2, that of m/512 Ce2Cl6 5.1 (due to the presence of C02).^ We pre- 

 pared solutions of m/128 KCl, m/192 MgCla, m/192 K2SO4, and 

 m/128 MgS04 of the same or even a slightly lower pH, namely 5.0 

 to 5.1. Table VI gives the balancing concentration of cane sugar 

 for the six solutions. 



We notice, first, that for the same pH of about 5.1 the salts with 

 bivalent cation show the characteristic low value for e, their at- 

 traction for water being less than that of the salts of K as well as of 

 La or Ce. 



' The pH of the distilled water used varied between 5.1 and 5.3 and this ac- 

 counts for the pH found in our solutions of neutral salts. 



