IONIC INTERACTIONS 



29 



carboxyl groups present at the surface of the ovalbumin 

 molecules. 



Ca++ + R.COo- ±> R.C02Ca+ 



(I) 



It will be seen that the results obtained in this way are in 

 excellent agreement with the experimental results. 



I therefore suggest that in the mechanisms which we 

 have just studied we have a rational approach to some 

 aspects of the interaction of ions with surfaces. We shall 

 now consider two examples of this. 



The sodiumi calcium ratio. It is very well known, indeed 

 so well known that of recent years no explanation has 

 been sought, that physiologically balanced salines, i.e. 

 salines which will support the life of tissues in a rela- 

 tively normal way, contain something of the order of 

 100 sodium ions to i calcium ion. It is difficult to con- 

 ceive any physico-chemical mechanism which would 



TABLE I 

 THE RATIO [Na"'"]:[Ca"'""''] in physiological fluids, and at 



