318 



ISOELECTRIC POINT OF RED BLOOD CELLS 



The observation by Joos^^ that the salt necessary for the agglutina- 

 tion of sensitized bacteria combined chemically with the bacteria, 

 since it was not to be detected in the supernatant fluid after aggluti- 

 nation, although not confirmed by later investigators, led me to inves- 

 tigate the removal of salt after acid agglutination. With cells washed 

 as free as possible from electrolyte, the amount of chloride present 

 was very small and consisted chiefly in that added as HCl. A test 

 for chlorine ion was made with AgNOs on the supernataiit fluid from 

 the cells, and it was found that at pH 4.8 no chloride was present, and 



20 



16 





6.0 5.0 4.0 3.0 pH 



Fig. 4. Curve showing the combination of red blood cells with hydrogen ion. 

 5 cc. of 10 per cent normal cells. The same curve is given with sensitized cells. 



only the slightest trace in the tubes to which considerable amounts 

 of HCl had been added, while on the alkaline side of pH 4.8 a distinct 

 turbidity appeared. 



This experiment was repeated many times, always with the same 

 result. The conditions were determined more accurately by volumet- 

 ric analysis of the fluid from tubes of cells to which small amounts of 

 m/10 NaCl were added along with m/10 HCl, so that each tube con- 

 tained exactly the same amount of chlorine ion. The results are 



" Joos, A., Z. Hyg., 1901, xxxvi, 422. 



