ION SERIES AND THE PHYSICAL PROPERTIES OF 

 PROTEINS. I. 



By JACQUES LOEB. 



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



(Received for publication, July 17, 1920.) 

 I. INTRODUCTION. 



It had been shown in a preceding paper^ that the relative influence 

 of ions on the rate of diffusion of water through collodion membranes 

 can be expressed by arranging the ions in two definite series, as follows: 



(1) Rb < K < Na < Li < divalent < trivalent cations. 



(2) CI < Br < I < divalent < trivalent anions. 



These results are intelligible on the assumption that we are dealing 

 in this case with electrostatic effects of ions, the electrostatic effects of 

 the cations being due to the excess charges of the positive nucleus and 

 the electrostatic effects of the anions being due to the charges of the 

 captured valency electrons. In this case the relative efficiency of 

 monatomic and monovalent cations should increase inversely with 

 the radius of the ion; and the relative efficiency of the monovalent, 

 monatomic anions should increase directly with the radius of the ion. 

 In the cation series the Li ion should be next to the divalent cations, 

 while in the anion series the iodion should be next to the divalent 

 anions. 



This order differs from that usually given for the action of ions on 

 the physical properties of proteins. Hofmeister^ and afterwards 

 Pauli^ determined the relative order of efficiency of ions for the pre- 

 cipitation of proteins. This order is according to Pauli: 



1 Loeb, J., /. Gen. Physiol, 1919-20, ii, 673. 

 ^ Hofmeister, F., Arch. exp. Path. u. Pharni., 1888, xxiv, 247. 

 ^ Pauli, W., Beitr. chem. Physiol, u. Path., 1903, iii, 225; Fortschr. naturwiss. 

 Forschung, 1912, iv, 237. 



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