ON THE ELECTRICAL CHARGE OF PROTEIN. *49 



last mentioned have an alkaline reaction in that upon 

 solution in water they increase the number of OH ions 

 present in it. This is brought about through the fact 

 that they combine with water and split hydrolytically into 

 sodium hydroxide and carbonic and phosphoric acids. 

 Since, however, sodium hydroxide is a stronger base than 

 carbonic and phosphoric acids are acids, more OH ions 

 exist in solution than H ions. If now we imagine the 

 sodium hydroxide to be replaced by the much weaker 

 calcium hydroxide, then the concentration of the free 

 OH ions will fall immediately. The chemical reaction 

 between the alkaline earths added to an animal fluid 

 and the phosphates and carbonates contained in it must 

 also act in this way in other words, toward the establish- 

 ment of an acid reaction in the fluid. It can readily be 

 shown even in an experiment with native protein to which 

 an alkali has been added and which reddens phenol- 

 phthalein very strongly that an acid reaction is produced 

 in the mixture as soon as calcium chloride is added to 

 it, as indicated by disappearance of the red color. In 

 this way the identical effects of acids and alkaline earths 

 upon negatively charged protein have found a ready 

 explanation. 



That the alkaline earths can act only indirectly through 

 their effects upon the salts of the serum is shown most 

 strikingly by an experiment in which calcium chloride is 

 added to salt-free serum. If sodium iodide or sodium 

 sulphocyanate is added to this mixture, no precipitate is 

 produced. If, however, the protein is rendered electro- 

 positive through the addition of a little acid, then the 

 sulphocyanate at once brings about a coarsely flocculent 

 precipitate. 



