JACQUES LOEB 705 



A similar experiment was made with different concentrations of 

 solutions of the chloride of crystalline egg albumin. The original 

 pH of the albumin chloride solution was 3.5 and that of the outside 

 solution 3.0. After equilibrium was established the pH both inside 

 and outside was slightly changed as is shown in Table V. The 

 osmotic pressures for j to 4 per cent solutions of albumin chloride 

 were measured and calculated for 2y -\- z — 2x. The difference, 

 which should be the osmotic pressure of the albumin particles in 

 solution, is found in the last row. It is almost identical with the dif- 

 ference found for gelatin chloride for the same concentration of gelatin. 



V. Difference between the Curves for Calculated and Observed Values. 



The curves representing the values for calculated osmotic pressures 

 differ in one or two respects from the curves representing the values 

 for the observed osmotic pressures. These differences are not great 

 but they are constant and can therefore not be due to an accidental 

 error. Fig. 3 shows the difference between the curves for the observed 

 and the calculated osmotic pressures in the case of a gelatin chloride 

 solution containing 1 gm. of originally isoelectric gelatin in 100 cc. 

 If we start with the ascending branch of the two curves of Fig. 3, we 

 notice that the observed osmotic pressures for pH 4.4 to pH 3.8 are 

 about 100 mm. higher in each case than the calculated pressures. 

 It may be a mere accident but 100 mm. happens to be the approxi- 

 mate value for the osmotic pressure of 1 gm. of gelatin in 100 cc. and 

 if the gelatin particles participate in the osmotic pressure of solutions 

 of gelatin salts our calculated values should be about 100 mm. lower 

 than the observed values for the same pH in the case of a 1 per cent 

 gelatin solution. Near the summit the difference becomes a little 

 less but we have seen that we may expect such irregularities on 

 account of experimental error. Besides at pH 3.4 the concentration 

 of the gelatin solution was diminished by about 20 per cent on account 

 of diffusion of water into the gelatin bag. The difference in the 

 ascending branch of the observed and calculated values occurs in 

 every experiment. 



The second constant difference between the curves for observed and 

 calculated osmotic pressures lies in the fact that the drop in the cal- 

 culated curves begins at a lower pH than the drop for the curves of 



