THE BEARING OF OSMOTIC PRESSURE 



87 



in the futuio development of colloidal chemistry, from which 

 much is to be expected. 



Then take the application of osmotic pressure to the action 

 of the primary cell, about which I must say only a word. The 

 primary cell was discovered by Volta more than a hundred years 

 ago, and its action was not understood until the present theory of 

 solutions was worked out by Van't Hoff and Arrhenius. Knowing 

 the osmotic pressure of the solutions around the two electrodes 

 in the primary cell, we are not only able to calculate the electro- 

 motive force of such cells, but are able to explain satisfactorily 

 the action of all the simpler forms of primarj^ cells. The bearing 

 of osmotic pressure, then, upon this fundamental chapter of elec- 

 trochemistry is obvious and most important. 



I should not close what I have to say in reference to osmotic 

 pressure, without adding a few words concerning the magnificent 

 measurements of osmotic pressure which have been, and are 

 being made by my colleague. Prof. H. N. Morse and his co- 

 workers. They have not only made the most accurate measure- 

 ments of osmotic pressure, but in doing this have overcome 

 difficulties which to any less skillful investigators would have been 

 considered as absolutely insurmountable. We now know the 

 osmotic pressures of cane sugar with accuracy certainly to the 

 second decimal, and over a very wide range in temperature. 

 This work is undoubtedly to be placed among the classics in 

 science for the difficulties met and overcome, and for the accuracy 

 of the measurements that are now being made. 



Just one word more in reference to the nature of osmotic 

 pressure. \Miat is osmotic pressure? Or what causes it? T do 

 not know nor do I believe that anyone else at present does. The 

 number of attempted explanations of what osmotic pressure 

 is or what causes osmotic pressure is literally legion. It seems 

 to me that nearly everj^one who has not anything better to do, 

 or who wishes to write a paper for which a suitable subject has 

 not been selected, favors us with his opinions as to what the nature 

 of osmotic pressure really is. 



As the result of reading more of these papers in the past than 

 I shall do in the future, I have come to the above conclusion 



