282 



HYDROGEN ION CONCENTRATION 



stated that the theoretical expectations were to a great extent 

 confirmed. 



First it appeared that glass becomes in most cases negatively- 

 charged towards aqueous solution. By means of high hydrogen ion 

 concentrations of the solution the current potential can be reduced to 

 zero, but the sign of the charge could not be reversed in this way. 

 Bivalent cations (Ba++) aboHsh the current potential in lower con- 



TABLE 42 



centrations than univalent cations. Trivalent cations (A1+++) reverse 

 the sign of the current potential even in the lowest concentrations, 

 while at higher concentrations the potential is reduced to zero again. 

 This was shown by the following experiment by Kruyt: Various 

 hquids were forced through a glass capillary and jaelded the values 

 for hydrodynamic current potential shown in table 42, at a water 

 pressure of 1 cm. of mercury. The concentrations are given in 

 micromols (1 /x-mol = 0.000,001 mol); a + sign before the value of 



