OF VITAL PHENOMENA 109 



the dilute side positive and hence favor positive osmosis by 

 electroendosmose, hence a membrane containing only such pores 

 would show only positive osmosis. Anions can diffuse through 

 the large pore, however, and since they diffuse faster than cations 

 in case of those salts effecting negative osmose, they give the 

 dilute side a, negative charge. The water, therefore, that is 

 charged positively (near the walls of the large pore) is pulled 

 through toward the dilute side. We have, then, in favor of 

 negative osmose, the electroendosmose and the water carried by 

 the electrolyte that diffuses toward the dilute side; whereas, 

 against negative osmose, we have the osmotic pressure of the 

 more concentrated solution exerted rather ineffectively against 

 a leaky membrane. It may be added that the explanation given 

 by Freundlich (1916) seems at least unnecessary. 



It was further observed by Hocker that not only the magni- 

 tude but also the direction of osmose is affected by changes in 

 concentration of the electrolyte. Negative osmose did not occur 

 with solutions more dilute than n/50. Perhaps at this dilution 

 the size of the negative ions is so increased by hydration as to 

 prevent them from passing through the pores. It would be in- 

 teresting to know whether more dilute solutions show negative 

 osmose with membranes having slightly larger pores. 



The experiments of Bethe (1911) and Bethe and Toropoff 

 (1914) may be interpreted as indicating that the charge in the 

 water half of the electric double layer over the porcelain is due, 

 in part at least, to H ions. They found that when an electric 

 current of more than one volt is passed from non-polarizable elec- 

 trodes through a Na 2 S0 4 solution, divided by a diaphragm of 

 gelatine, jelly, collodion, agar-agar, albumin, bladder, gold beaters 

 skin parchment, carbon or clay, the anode side becomes alkaline 

 and the cathode side acid, whereas water passes toward the 

 cathode. Thus water and hydrogen ions pass in the same direc- 

 tion. The water therefore that is charged positively contains 

 an excess of H ions, which must give it at least part of its posi- 

 tive charge. The side of the membrane toward the anode is 

 alkaline on account of the removal of hydrogen ions. It is im- 

 possible for the massing of anions against a non-metallic mem- 

 brane to cause an acid reaction, since there is no means of rob- 

 bing them of their charges. 



