IONIZING INFLUENCE OF SALTS WITH TRIVALENT 



AND TETRAVALENT IONS ON CRYSTALLINE EGG 



ALBUMIN AT THE ISOELECTRIC POINT. 



By JACQUES LOEB. 

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



(Received for publication, May 17, 1922.) 



I. 



INTRODUCTION. 



Measurements of the membrane potentials between aqueous pro- 

 tein solutions or gels and surrounding water at equilibrium have 

 yielded the result that salts with trivalent cations give isoelectric 

 protein a positive charge while salts with tetravalent anions give it 

 a negative charge.^ On the basis of Donnan's theory of membrane 

 potentials it was assumed that salts with trivalent cations, e.g. 

 LaCls, form with isoelectric protein ionizable salts which result in 

 the formation of positive protein-La ions and negative CI ions; and 

 that salts like Na4Fe(CN)6 form with isoelectric protein salts which 

 result in the formation of negative protein-Fe (CN)6 ions and positive 

 Na ions.' In other words, salts with trivalent cations react with 

 isoelectric protein like acids, and salts with tetravalent anions react 

 with isoelectric protein like alkalies; with this difference, however, 

 that the compounds of isoelectric gelatin with acids and bases are 

 much more stable than those with the salts of trivalent cations or 

 tetravalent anions. Salts with divalent ions like Na2S04, CaClo, 

 or salts with monovalent ions like NaCl, did not produce any measur- 

 able charge on isoelectric gelatin in aqueous solutions. Experiments 

 on anomalous osmosis through gelatin-collodion membranes were in 

 harmony with these results.^ 



iLoebJ.,/.Cf«.P//>'5w/.,1921-22,iv,741. 



' Loeb, J., Proteins and the theory of colloidal behavior, New York and London, 

 1922, 165. 



» Loeb, J., /. Gen. Physiol, 1921-22, iv, 463. 



75'; 



