OSMOTIC PRESSURE 



177 



We can, therefore, say that (with the exception of two minor 

 discrepancies to be discussed further on) the Donnan equilibrium 

 accounts not only qualitatively but almost quantitatively for 

 (a) the valency effect of the anion with which the gelatin is in com- 

 bination; (b) for the effect of the pH. 



s 



450 

 425 

 400 

 375 

 350 

 325 

 300 

 275 

 250 



225 



a 200 



t/2 



O 175 



150 



.125 



100 



75 



50 



25 



t- 



smoti 



7o(>ektin 



: presi 



chl 



OP( 



)rice 



\ 



\ 



pH 1.6 IB 20 2.2 2.4 26 2.8 3.0 3.2 34 3.6 3.8 4.0 4.2 4.4 4.6 



FIG. 45. Showing agreement and minor discrepancies between the curves 

 of observed and calculated osmotic pressures of 1 per cent gelatin chloride 

 solutions. 



A glance at the formulae will show us that this influence of 

 the pH on osmotic pressure te a mathematical consequence of 

 12 



