﻿at the Boundary between a Liquid and a Gas. 39 1 



Three examples are given for slightly greater concentra- 

 tions : — 



No. 6. 



Concentration. 



Equivalents 



per c.c. 



Diameter of 

 sphere 

 in mm. 



Sign 

 charo 



10- 9 x6-6 



0-53 









041 









0-35 



+ 





0-17 



+ 





0-08 



+ 



No. 7. 



Concentration. 



Equivalents 



per c.c. 



10" 9 X6-6 



Diameter of 

 sphere 

 in mm. 



0-35 



0-28 

 0-26 

 0-17 

 0-14 



Sign of 

 charge. 



Concentration. 



Equivalents 



per c.c. 



10" 9 x8 



No. 8. 



Diameter of 

 sphere 

 in mm. 



0-44 



035 



017 



Sign of 

 charge. 



Almost zero. 



Above a concentration of 10~ 9 X 8 the bubbles were always 

 positive. 



The examples given show that the spheres do not all have 

 the same size when they reach the zero — isoelectric — point 

 in a given solution. The larger a sphere is at the beginning 

 the larger it is when its charge becomes zero. This suggests, 

 as the cause of the change in sign, a kind of coagulation of 

 something in the free surface. 



It is known that, in a solution of thorium nitrate in water, 



