AMPHOTERIC COLLOIDS. 

 I. Chemical Influence of the Hydrogen Ion Concentration. 



By JACQUES LOEB. 



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



(Received for publication, July 26, 1918.) 



It is often stated (Pauli, Hober, and others) that both ions of a 

 neutral salt affect the physical properties of an amphoteric electro- 

 lyte (ampholyte) simultaneously and in the opposite sense; so that 

 the total result is the algebraic sum of the opposite action of the 

 oppositely charged ions of the neutral salt.^ The writer has been 

 able to show by experiments on gelatin and on pig's bladder that 

 this statement is not correct, but that apparently only one of the 

 two ions of the neutral salt acts upon the ampholyte; namely, the one 

 which has the opposite electric charge from that of the ampholyte.^ 



The hydrogen ion concentration of the gelatin solution used by the 

 writer was 10~^ (or in Sorensen's logarithmic symbol pH = 7.0) 

 and this gelatin reacted with neutral salts as if it were an anion 

 capable of combining with the cation of a neutral salt. When, 

 however, powdered gelatin is treated for some time with an acid, 

 e.g. HCl, gelatin chloride (or hydrochloride) is formed, which is 

 supposed to dissociate electrolytically into a positive gelatin ion and 

 a negative chlorion. The writer found that when the supernatant 



^ This and other erroneous statements current in colloid chemistry are due to 

 the fact that the previous investigators always studied the action of neutral salts 

 upon proteins in the presence of the salt. The writer removed these salts after 

 they had a chance to act on the gelatin. This procedure is necessary on account 

 of the fact that the manifestation of the effect of the electrolyte upon the gelatin 

 is repressed in the presence of the electrolyte. 



^ Loeb, J., /. Biol. Chem., 1917, xxxi, 343; 1918, xxxiii, 531; xxxiv, 77, 395, 

 489; 1918, xxxv, 497. 



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