Vol. 36 



BULLETIN 



I No 6 



OF THE 



TORREY BOTANICAL CLUB 



JUNE, 1909 



Osmotic theories, with special reference to van^t Hoff's law 



J. B. Dandeno 



Osmotic action is a phenomenon referred to in nearly all text- 

 books on physics, in many works on physical chemistry, and in 

 practically all books which deal with physiological phenomena, 

 whether relating to plant or animal. In these same text-books, 

 whether relating to physics, chemistry, or biology, one will look 

 in vain for a satisfactory explanation of osmotic processes. In 

 fact a variety of definitions will be found, some relating to diffusion 

 merely, some relating to osmosis and diffusion in a general way, 

 some relating to osmosis particularly, but all more or less vague ; 

 and, when relating to pressure produced by osmotic action, some- 



■ 



times confusing and contradictory. Of course, osmotic activities 

 in themselves are physical phenomena purely; but as they bear 

 so important a part in relation to physiological operations, they 

 are dealt with frequently in works on biology. But it is to the 

 physical chemist, perhaps, to whom we must look for more light 

 with respect to the operations underlying osmotic processes. 



It is not intended here to go into a history of the subject, yet, 

 in order to understand the question in its relationships, it is neces- 

 sary to give a few points of a historical nature. 



The phenotnenon of osmosis, first observed in relation to or- 

 ganisms, crept into the text-books and other books on physics, 

 and was dealt with there in connection with diffusion and dialysis 

 rather than as osmosis merely. In such books we have to read 

 through such terms as colloid and crystalloid before we come to 

 osmosis. As a matter of fact, however, colloid and crystalloid 



[Th 



1 909. J 



283 



