THE INFLUENCE OF ELECTROLYTES ON THE ELECTRI- 

 FICATION AND THE RATE OF DIFFUSION OF WATER 

 THROUGH COLLODION MEMBRANES. 



By JACQUES LOEB. 

 {From the Laboratories of The Rockefeller Institute for Medical Research.) 



(Received for publication, May 24, 1919.) 

 I. INTRODUCTION. 



The direct measurements of the osmotic pressure of sugar solutions 

 by Morse^ and his fellow workers as well as by Lord Berkeley and 

 Hartley^ show so close an approximation to the values calculated on 

 the basis of van't Hoff's theory that it is difficult to doubt the cor- 

 rectness of this theory. As Fick^ pointed out as early as 1866, we 

 can, on the assumption of the validity of the kinetic theory, treat a 

 solution as a mixture of two gases, the solvent and the solute. When 

 the solution is separated from the pure solvent by a semipermeable 

 membrane more molecules of the solvent will impinge in the unit of 

 time on the unit area of the membrane on the side of the pure solvent 

 than on the side of the solution and hence the solvent will diffuse to 

 the solution until the partial pressure of the solvent on the solution 

 side becomes so great, that the number of molecules of solvent im- 

 pinging on the unit of membrane on the solution side becomes equal 

 to the number of molecules impinging on the unit of membrane on 

 the side of the pure solvent. 



There are, however, phenomena which suggest that in addition to 

 the gas pressure other forces may enter into the problem of diffusion 

 of water through a membrane. Such phenomena are the cases of 



^ Morse, H. N., The osmotic pressure of aqueous solutions, Carnegie Institu- 

 tion of Washington, Publication 198, 1914. 



^ Earl of Berkeley, and Hartley, E. G. J., Proc. Roy. Soc. London, Series A, 

 1916, xcii, 477. 



^ Fick, A., Die medizinische Physik., Braunschweig, 1866, 2nd edition, 36; 

 Z. physik. Chem., 1890, v, 526. 



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