PREFACE 



Colloid chemistry has been developed on the assumption that 

 the ultimate unit in colloidal solutions is not the isolated molecule 

 or ion but an aggregate of molecules or ions, the so-called micella 

 of Naegeli. Since it seemed improbable that such aggregates 

 could combine in stoichiometrical proportions with acids, alkalies, 

 or salts, the conclusion was drawn that electrolytes were adsorbed 

 on the surface of colloidal particles according to a purely empirical 

 formula, Freundlich's adsorption formula. 



The writer's investigations have led to the result that this last 

 conclusion is based on a methodical error, as far as the proteins 

 are concerned ; namely, to the failure to measure the hydrogen ion 

 concentration of the protein solutions, which happens to be one of 

 the main variables. When the hydrogen ion concentrations are 

 duly measured and considered, it is found that proteins combine 

 with acids and alkalies according to the stoichiometrical laws of 

 classical chemistry and that the chemistry of proteins does not 

 differ from the chemistry of crystalloids. 



As long as chemists continue to believe in the existence of a 

 special colloid chemistry differing from the chemistry of crystal- 

 loids, it will remain impossible to explain the physical behavior 

 of colloids in general and of proteins in particular. This state of 

 affairs is reflected in the concluding remarks of Burton's interest- 

 ing book on "The Physical Properties of Colloidal Solutions" 

 published in 1920, 



"We may very well conclude with the words used by the pioneer 

 worker Zsigmondy, in closing his first account of the early work on 

 colloidal solutions: 



'From the foregoing outline no general theory of colloids can be 

 given, for the study of colloids has become a great and extensive science, 

 in the development of which many must assist; only when the volu- 

 minous material supplied by much physico-chemical research has been 

 properly systematized, will the theory of colloidal solutions be raised 

 from mere consideration of the similarities in special cases to the standing 

 of an exact science.'" 



