CHEMISTRY: J. WEB 
441 
time it had been known that in certain cases water is able to diffuse 
from solutions of higher to solutions of lower concentrations, and it has 
been suggested by a number of authors, e.g., Girard,^ Bartell,^ Bern- 
stein,^ and others that these phenomena are due to electrical forces 
caused by the presence of electrolytes in solution. They assume on the 
basis of the experimental and theoretical work done by Quincke, Helm- 
holtz, Perrin,^ and others on electrical endosmose that differences of 
electrical potential on both sides of the memibrane influence the rate of 
diffusion of water through the membrane. 
The writer has recently investigated the influence of electrolytes 
on the rate of diffusion of water through collodion bags prepared in a 
definite and uniform way and bathed over night in a 1 per cent gelatin 
solution. The bags had the shape of Erlenmeyer flasks with 50 cc. con- 
tents and were closed by rubber stoppers which were perforated by a 
glass tube with a bore of 2 mm., the tube serving as a manometer. 
When such a bag was filled with watery solution and was dipped into 
distilled water the level of the water in the manometer rose owing to 
the fact that more water diffused from the pure water into the solution 
than diffused simultaneously in the opposite direction, as was to be 
expected. It was found that the initial rate of diffusion of water was 
influenced in an entirely different way by electrolytes and non-electro- 
lytes. The solutions of non-electrolytes, e.g., sugars, influenced the 
initial rate of diffusion of water through the membrane in proportion to 
their concentration and this influence began to show itself when the con- 
centration of the sugar was above M/64 or M/32. Sugar solutions of 
lower concentrations than M/64 caused no rise in the manometer. We 
will call this effect of the concentration of the solute on the initial rate 
of diffusion the gas pressure effect. Solutions of electrolytes show this 
gas pressure effect also, but it commences at somewhat higher concen- 
trations than M/64, namely at M/16 or even M/8. Solutions of 
electrolytes of a lower concentration than M/16 or M/8 have a specific 
influence on the rate of diffusion of water through the membrane which 
is not found in the case of non-electrolytes. 
When we separate a watery solution of an electrolyte of a concentra- 
tion below M/16 from pure water by a collodion membrane, the water 
molecules diffuse through the membrane as if they were electrically 
charged — positively or negatively according to the nature of the ions 
present — and as if they were attracted electrostatically by ions of one 
sign and repelled by ions of the opposite sign. When we used solutions 
of electrolytes theoretically isosmotic with a M/64 cane sugar solution 
