ELECTRICAL CHARGES OF COLLOIDAL PARTICLES AND 

 ANOMALOUS OSMOSIS. 



II. Intluence of the Radius of the Ion. 



By JACQUES LOEB. 



(Front the Laboratories of The Rockefeller Institute for Medical Research.) 



(Received for publication, March 21, 1922.) 



The valency and sign of charge of ions are not the only variables 

 influencing anomalous osmosis. A third variable is the radius of the 

 ion. The radius of the ions of the alkah metals increases in the order 

 of Li < Na < K. The writer has shown that when solutions of pH 

 3.0 of the chlorides or nitrates of these cations are separated from 

 a solution of water also of pH 3.0 by collodion-gelatin membranes, 

 water diffuses into the salt solution with a rate increasing inversely 

 with the radius of the cation.^ This is illustrated in the transport 

 curves in Fig. 1 where the abscissae are the concentration of the salt 

 and the ordinates the number of millimeters to which the level of 

 liquid has risen in 20 minutes in the manometer connected with the 

 solution. It is obvious that the rise is greatest for LiCl, less for 

 NaCl, and still less for KCl. This confirms the results of a preceding 

 publication. 



It is also obvious that the three transport curves in Fig. 1 show the 

 initial rise to a maximum at about m/16 followed by a drop which is 

 followed by a second rise. This second rise will not interest us here 

 since it is mainly or exclusively the expression of the transport of liquid 

 due to osmotic forces. ^ Only part of the curves, namely, between the 

 concentration from to a concentration of m/4, is due to electrical 

 forces, and only these forces interest us in this connection. 



The question arises, What determines this influence of the radius 

 of the monatomic and monovalent cations on the electrical transport 



J Loeb, J., 7. Gen. Physiol., 1919-20, ii, 673. 

 ^Loeb, J., J. Gen. Physiol., 1919-20, ii, 173; 1921-22, iv, 463. 



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