JACQUES LOEB 555 



When we plot the osmotic pressure of these solutions as ordinates 

 over the pH as abscissae (Fig. 5), we notice that the curves for the 

 osmotic pressure of Na and K caseinate are alike; the curves for the 

 casein salts are, however, over three times as high when the cation 

 is monovalent (Na or K) than when the cation is bivalent (Ca or Ba). 

 This is, however, chiefly the result of the fact that Ca and Ba caseinate 

 are incompletely soluble up to a pH of 10.5. 



Fig. 6 gives the viscosity curves for Na caseinate and Ba caseinate. 

 The difference in height between the two casein salts is between pH 

 11 and 12 of a similar order as in the case of Na and Ba gelatinate. 



SUMMARY AND CONCLUSION. 



The experiments on casein solutions therefore confirm the con- 

 clusion at which we arrived from the behavior of gelatin and crystal- 

 line egg albumin that the forces determining the combination between 

 proteins and acids or alkalies are the same forces of primary valency 

 which also determine the reaction between acids and alkalies with 

 crystalloids, and that the valency and not the nature of the ion in 

 combination with a protein determines the effect on the physical 

 properties of the protein. 



The measurements mentioned in this paper were made by Dr. E. 

 Brakeley, Mr. M. Kunitz, and Mr. N. Wuest of this Laboratory, to 

 whom I wish to express my indebtedness. 



