CHEMICAL PHENOMENA IN LIFE 



any difference in the osmotic pressure theoretically 

 calculated from the number of molecules. So we 

 must believe that colloidal solutions are never 

 electrolytes, but are always molecular solutions. 



The depression of the freezing-point in solutions 

 is less in proportion as the molecular weight of 

 the substance dissolved is greater. If colloidal 

 solutions only show a very slight depression, or one 

 which lies beyond the limits of exact observation, 

 the conclusion is evident that colloidal substances 

 have a very considerable molecular weight. It 

 was extremely interesting for physiology to learn 

 that exactly those substances which are most im- 

 portant for life possess a very high molecular weight 

 and consequently very large molecules in com- 

 parison with inorganic matter. For example, 

 egg-albumin is said to have the molecular weight 

 of at least 15,000, starch more than 30,000, whilst 

 the molecular weight of hydrogen is 2, of sulphuric 

 acid and of potassium nitrate about 100, and the 

 molecular weight of the heaviest metal salts does 

 not exceed about 300. 



Thus we come to the hypothesis that the size 

 of the molecules of dissolved colloids is considerably 

 larger than the size of those of crystalloids. It is of 

 great interest that in living protoplasm such large 

 molecules are characteristic of its chemical structure. 



Graham believed that colloids and crystalloids 

 are not connected with each other by substances 

 of intermediate character. They were rather said 



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