242 THEORY OF COLLOIDAL BEHAVIOR 



to the solution. The micella theory would explain this by assum- 

 ing that the addition of a salt increases the degree of aggregation 

 in the solution and hence diminishes the number of isolated par- 

 ticles and therefore the osmotic pressure of the solution. This 

 assumption cannot be put to a quantitative test since we have no 

 direct method of determining the number of aggregates in solu- 

 tion. We have shown, however, in this chapter that if we in- 

 crease the number of aggregates at the expense of isolated protein 

 ions or molecules, the viscosity rises. Hence, if we assume that 

 the number of aggregates in the gelatin chloride solution is 

 increased through the addition of salt, the viscosity of such a 

 solution should increase for the same reason; whereas in reality 

 we have seen that the addition of salt depresses both the osmotic 

 pressure and the viscosity of the gelatin solution. This fact 

 eliminates the aggregation or micella theory as a possible source 

 of explanation of the colloidal behavior. We need not deplore the 

 loss, since the application of the aggregate theory to the explana- 

 tion of colloidal phenomena has never risen beyond the stage of 

 vague speculations. 



