JACQUES LOEB 



253 



The results of our experiments on swelling are expressed in Figs. 1, 

 2, and 3. The abscissae in Fig. 1 are the pH found in the gelatin 

 after equilibrium was established. The ordinates represent the fig- 

 ures for the volume of the granules of 1 gm. of gelatin in different 

 acids. It is obvious that in all cases the volume (or swelling) is a 



pH 1 



6 



Fig. 1. Influence of HCl, HNO3, H3PO4, H2SO4, trichloracetic, and oxalic 

 acids on the swelUng of gelatin. Abscissae are the pH, ordinates the volume of 

 gelatin. The curves for all the acids are practically identical except that for 

 H2SO4 which is about one-half as high as the curves for the other acids. 



minimum at the isoelectric point pH = 4.7, that it rises with dimin- 

 ishing pH until the maximum is reached at a pH of about 3.2 or Z.Z, 

 and that the curve drops steeply with a further diminution of pH 

 {i.e. a further increase of hydrogen ion concentration). The fact that 

 the maximum lies here at pH of about 3.2, while in our osmotic pres- 

 sure curves it was at about Z.Z or 3.4, indicates the degree of error in 



