624 



eiectrolyles exert uii llie charge of a glass capillar}' is quantitatively 

 tlie same as that exerted on the colloidal particle during the coagulation. 



2, As regards the order of the ion-actions, it has been pointed 

 out in the previous paper that the ions discharge more strongl}', 

 when their valency is higher and that the heavy metals exert more 

 influence tlian the light ones of equal valency. It is well-known 

 that the limit values for the coagulation of suspensoids just exhibit 

 the same peculiarities. 



3. In order to make a quantitative comparison it should be first 

 observed that the limit values for KCl and BaClj in the same sol. 

 are generally in the proportion of about 60: 1. In contact with 

 either of tiiese solutions the charge of the particle thus gets equally 

 diminished. We may, therefore also expect that the charge of a glass 

 capillary will be lowered by a solution of KCl to the same extent 

 as by the sixty times weaker BaCl^ solution. Hence, when from the 

 tables in the preceding paper vnc calculate the charge in concen- 

 trations of KCl and BaCl, in the said proportion, those should be 

 eijual if the idea as to the limit value just revealed is a correct one. 



The calculation of the charge is })0ssible according to the theory 

 developed by HELMHOJiTZ ^). The current potential is sequel to the 

 electric double layer formed at the wall of the capillary and is 

 related to the electric moment M as follows. 



E = M-P (1) 



n 



in which co represents the specific resistance and ^] the constant of 

 the internal friction whilst P represents the pressure employed. For 

 comparison purposes we can consider the electric moment of the double 

 layer just as well as the charge ? per unit of section, as it is in 

 inverse proportion therewith. 

 We write equation (1) : 



E n 



Pea 



If now we indicate the quantities relating to a BaClj- solution 

 with the index t>, those relating to the 60 times more concentrated 

 solution of KCl with the index k, then on the strength of the aboxe 



considerations we must get 



PJb Oih \Pjk 0)k 



(' Wied. Ara. 7, 337 (1879). 



