: 1027 
OH —|— H OH —|—… H 
Fig. 2. 
illustrates Prrrin’s ') results, as he measured the electro endosmosis 
of a naphtalene membrane. Fig. 2B shows the results of Eris’ 
investigations?) and Fig. 2C completes that representation by adding 
the results of this communication, It is still. difficult to give a 
decision whether the minimum lies exactly at the iso-electrie point 
or not. 
6. Finally we must inquire into the cause of the increase 
of the electric charge in diluted solutions and we have to look for 
points of agreement with the theory of selective adsorption of ions. 
Powis *) too discussed this question. 
The adsorption of ions by a surface with an electric charge of 
the same sign as that of the ions does not form an exceptional 
case. Lately Freunpiich and Poser‘) mentioned a similar pheno- 
menon when studying the adsorbents with positive and negative 
electric charge. °) 
They found bolus (negative charge) did not adsorb dye-anions 
but that aluminium oxide did adsorb cations, some of them (chry- 
soidin, malachit green) even to a high degree. 
“Dies erklärt sich unserer Meinung nach einfach damit, dass 
die adsorbierende Oberfläche keineswegs. mit dem aktiven Elektro- 
lyten, der die Ladung bedingt — gesättigt zu sein braucht; sie kann 
also sehr wohl neben diesem Stoff noch weitere adsorbieren, genau 
wie etwa Kohle, die eine nicht zu grosse Menge Benzoesäure ad- 
sorbiert hat, noch Oxalsäure aufzunehmen vermag” (p. 318). 
1) Journ. de chim. phys. 2 601 (1904). 
2) loc. cit. spec. I p. 348 and Il p. 606. 
8) Z. f. physik. Chem.°89, 103—105, (1915). 
4) Koll. Beih. 6, 297 (1914). | 
5) MicHaAËLIs and Lacus, Z. f. Elektrochemie 17, 1 (1911), as well as Kruyt 
and van Duin, Koll. Beih. 5, 269 (1914) found that negatively charged charcoal 
adsorbed more Cl than K out of a KCI solution. 
