OSMOTIC PRESSURE 



173 



show not only the same qualitative characteristics as the curves 

 for the observed osmotic pressures in Fig. 44, but show them 

 almost quantitatively; except that a correction for the value of 

 osmotic pressure due to the gelatin particles themselves has to be 

 added, a point which will be discussed later. What is of im- 



pH 1.4 1.6 IS 20 22 2.4 2.6 2.8 3.0 32 3.4 a6 3.8 4.0 42 44 4.6 4fi 



FIG. 43. Calculated curves of osmotic pressure taken from the data of the 

 experiments represented in Fig. 44. The calculation is made on the basis of the 

 validity of Donnan's theory of membrane equilibrium. The calculations lead to 

 curves resembling the curves in Fig. 44 in all essential points, in regard to valency 

 effect of the anion, as well as in regard to influence of pH (see legend under 

 Fig. 44). 



portance here is the following : The curves for osmotic pressure 

 calculated on the basis of the Donnan equation and plotted in 

 Fig. 43 resemble the curves for the osmotic pressure observed in 

 the same experiments represented in Fig. 44 in the following 

 essential points. 



