JACQUES LOEB 



771 



The bags were put over night at 21°C. into beakers containing each 

 350 cc. of 0.001 N HCl in water. The next day the osmotic pressure 

 was read, the p.d. between the gelatin chloride solution and the out- 

 side aqueous solution free from gelatin was measured (with a Comp- 

 ton electrometer and indifferent saturated KCl-calomel electrodes), 

 and the pH inside and outside was determined with the hydrogen 

 electrode. Table I gives the results of these observations. 



TABLE I. 



Influence of Substitution of Powdered for Dissolved Gelatin on Osmotic Pressure 



and p. D. 



Powdered gelatin per 100 cc, 

 gm 



Dbsolved gelatin per 100 cc, 

 gm 



Osmotic pressure 



pH inside 



pH outside 



pH inside minus pH outside . . 



P.D. calculated, millivolls 



Membrane potentials observ 

 ed, millivolts 





 0.8 



398 

 3.Zi 

 2.87 

 0.46 



26.5 

 27.0 



The table confirms the writer's former observation that the osmotic 

 pressure of the gelatin solution diminishes the more the more of the 

 dissolved gelatin is replaced by powdered gelatin. The latter ob- 

 viously does not participate in the osmotic pressure. 



The table shows furthermore that the p.d. observed at equilibrium 

 between the gelatin solution and the outside aqueous solution varies 

 much less than the osmotic pressure. It became necessary to ascer- 

 tain whether or not this p.d. across the membrane which was 

 measured with the aid of two indifferent electrodes (saturated KCl- 

 calomel solution) was actually determined by the difference in the 



