JACQUES LOEB 



277 



the absorption of CO2 from the air and this diminished the concen- 

 tration of NaOH in the outside and, as a consequence, also in the 

 inside solution. 



Fig. 1 represents the osmotic pressure reached after about 5 hours 

 in the various solutions. (At this time the permanent osmotic 

 pressure is generally attained when the solution undergoes no further 

 chemical changes.) The abscissae of Fig, 1 are the logarithms of the 

 concentration of the NaOH. The row of figures below the figures 

 for the concentration of NaOH is the pH as found in each gelatin 

 solution at the end of the experiment. The ordinates are the osmotic 



a 



o 



•1—1 

 to 



£ 



120 

 100 

 80 

 60 

 40 

 20 



Cone, of NaOH 



_riiii3_Tiriririii n 



4000 2000 1000 500 250 125 62 31 15 

 pn 4.65 4.9 5.0 53 84 ItO llfl 122 124 12.6 



Fig. 2. Curve of initial rate of diffusion of water into 1 per cent gelatin dissolved 

 in the same concentrations of NaOH as those used in Fig. 1, measured by rise of 

 level of liquid in manometer 30 minutes after beginning of experiment. Abscissae 

 are the concentrations of NaOH, ordinates are the rise of level of liquid in manom- 

 eter after 30 minutes. The curve is similar to the curve of osmotic pressure. 

 Maximum at pH = 8.4. 



pressures expressed in mm. of a column of 1 per cent gelatin solution. 

 The maximum should have been at a pH of about 8.4 (between 

 m/ 1,000 and m/500). The figure shows that the osmotic pressure 

 rises first rapidly with an increase in the pH and falls equally rapidly 

 beyond a pH which (from other experiments) we judge to be about 

 8.4. At a pH of 12.2 the curve is almost as low as it is for isoelectric 

 gelatin. 



