■JACQUES LOEB . 199 



SUMMARY. 



1. When a watery solution is separated from pure water by a col- 

 lodion membrane, the initial rate of diffusion of water into the solution 

 is influenced in an entirely different way by solutions of electrolytes 

 and of non-electrolytes. Solutions of non-electrolytes, e.g. sugars, in- 

 fluence the initial rate of diffusion of water through the membrane 

 approximately in direct proportion to their concentration, and this 

 influence begins to show itself under the conditions of our experiments 

 when the concentration of the sugar solution is above m/64 or m/32. 

 We call this effect of the concentration of the solute on the initial rate 

 of diffusion of water into the solution the gas pressure effect. 



2. Solutions of electrolytes show the gas pressure effect upon the 

 initial rate of diffusion also, but it commences at a somewhat higher 

 concentration than m/64; namely, at m/16 or more (according to the 

 nature of the electrolyte). 



3. Solutions of electrolytes of a lower concentration than m/16 or 

 m/8 have a specific influence on the initial rate of diffusion of water 

 through a collodion membrane from pure solvent into solution which 

 is not found in the case of the solutions of non-electrolytes and which 

 is due to the fact that the particles of water diffuse in this case through 

 the membrane in an electrified condition, the sign of the charge de- 

 pending upon the nature of the electrolyte in solution, according to 

 two rules given in a preceding paper.^ 



4. In these lower concentrations the curves representing the influ- 

 ence of the concentration of the electrolyte on the initial rate of dif- 

 fusion of water into the solution rise at first steeply with an increase 

 in the concentration, until a maximum is reached at a concentration 

 of m/256 or above. A further increase in concentration causes a drop 

 in the curve and this drop increases with a further increase of concen- 

 tration until that concentration of the solute is reached in which the 

 gas pressure effect begins to prevail; i.e., above m/16. Within a 

 range of concentrations between m/256 and m/16 or more (according 

 to the nature of the electrolyte) we notice the reverse of what we 

 should expect on the basis of van't Hoff's law; namely, that the at- 

 traction of a solution of an electrolyte for water diminishes with an 

 increase in concentration. 



