1025 
The less recent researches of Eris *) do not clash with my results 
either, he found an optimum only in the case of NaOH, but if we 
pay attention to the concentrations of his experiments it is clear 
again that it was impossible for him to have observed the other 
maxima. 
The relation between the four curves in our, fig. 1 is most remark- 
able from the point of view of colloid chemistry. It is well known 
that all anorganic ions are adsorbed in nearly the same molecular 
concentration with exception only of the ions H and OH (and those 
of the heavy metals). Considering that the Cl-ions have a tendency 
to give a higher charge to the adsorbing surface, we can easily 
understand that the ion of potassium causes much less resistance 
to the increase’ of the negative charge than the highly absorbative 
ions of H and pCIC,H,NH, and the Ba-ion, which is absorbed in 
a normal way, but bears the double electric charge. Therefore we 
find with KCl a plain optimum, which is noticeable even in rather 
strongly concentrated solutions; with the other three ions the opti- 
mum is reached at a concentration from 50— 100 u Mol and the 
curve is rather pointed, especially with the anilene- and the Ba-ion. 
Powis’ results regarding the influence of the anions and Erus’ 
regarding that of the OH-ion are in agreement with these con- 
clusions. 
It is worth observing that the charges of contact for the different 
electrolytes at a certain concentration show the same sequence as 
the corresponding limit values with colloids, but only at concentra- 
tions somewhat higher than those of the maxima. The descending 
branches e.g. at a concentration of 1000 qu Mol. p. L. show the 
sequence K:, H:, An: and Ba; the limit values’) for the floculation 
of the As,S, sol are (m. Mol p. L.) 
KCI50 HCl 31 pCIC,H‚NH,HCI 1.08 
BaCl, 0.69. 
To test a quantitative relation between electric charge and limit 
value (as I tried to do in a previous paper) it is necessary to make 
use only of the values of the descending branches of fig. 1. For 
that purpose a close investigation of these branches will be necessary 
but cannot be made with the apparatus I have used till now. I 
hope that I shall be able before long to continue these researches 
with an apparatus fit for experiments at higher pressures. 
1) Z. f. physik. Chem. I 78, 321 (1912); Il 80, 597 (1912); IIL 89 145 (1915). 
2) FREUNDLICH, Kapillarchemie p. 351 (Leipzig 1909), 
