JACQUES LOEB 105 



submersed in water are therefore comparable to those in our experi- 

 ments except that we substitute a collodion membrane for the gelatin 

 membrane. 



The writer has shown that metal gelatinates of the same con- 

 centration of gelatin and of hydrogen ions swell much more when 

 the metal in combination with the gelatin is monovalent (e.g. Li, 

 Na, K, or NH4) than when it is bivalent {e.g. Ca or Ba).^ When 

 gelatin is a cation the swelling is greater when the anion in com- 

 bination with gelatin is monovalent {e.g. CI, NO3, or H2PO4) than 

 when it is bivalent {e.g. 804).^" The curves representing the influ- 

 ence of different acids and alkalies on the swelling of gelatin are 

 similar to the curves representing the influence of the same acids 

 and alkalies on the osmotic pressure of gelatin solutions. This 

 similarity becomes clear if we adopt Procter's osmotic theory of 

 swelling, adding to it our theory of the role of the electrification of 

 particles of water in the phenomena of osmosis. In these experi- 

 ments the solution surrounding the block of gelatin salt must have 

 a low concentration of electrolyte since the presence of an excess 

 of electrolyte suppresses the swelling, as pointed out in previous 

 publications. 



SUMMARY. 



1, Amphoteric electrolytes form salts with both acids and alkalies. 

 It is shown for two amphoteric electrolytes, A1(0H)3 and gelatin, 

 that in the presence of an acid salt water diffuses through a collodion 

 membrane into a solution of these substances as if its particles were 

 negatively charged, while water diffuses into solutions of these elec- 

 trolytes, when they exist as monovalent or bivalent metal salts, as 

 if the particles of water were positively charged. The turning point 

 for the sign of the electrification of water seems to be near or to 

 coincide with the isoelectric point of these two ampholytes which 

 is a hydrogen ion concentration of about 2 X 10~^ N for gelatin and 

 about 10-^ N for A1(0H)3. 



2. In conformity with the rules given in a preceding paper the 

 apparently positively charged water diffuses with less rapidity through 

 a collodion membrane into a solution of Ca and Ba gelatinate than 

 into a solution of Li, Na, K, or NH4 gelatinate of the same concentra- 



