Variable Acidity of Hemoglobin. 181 



with which the blood has been brought into equilibrium has in 

 each instance been analyzed for carbon dioxide and oxygen after 

 equilibrium has been reached. 



From the data obtained the hydrogen ion concentration has 

 been calculated from the ratio of free dissolved carbonic acid to 

 bicarbonate. When the concentration of bicarbonate has been 

 plotted against the hydrogen ion concentrations, curves similar to 

 those given by L. J. Henderson in a recent paper 1 have been ob- 

 tained, showing an isohydric shift of base between hemoglobin 

 and the other constituents of the blood, according to whether the 

 hemoglobin was oxygenated or reduced. When the bicarbonate 

 was plotted against the logarithm of the figure obtained for the 

 hydrogen ion concentration a linear relationship was found. 



On plotting the serum chlorides against the hydrogen ion 

 concentration an isohydric shift of chlorides has been noted in 

 every experiment — i.e., at the same hydrogen ion concentration 

 the concentation of chlorides in the serum is higher in the case 

 of oxygenated blood than in the case of reduced blood, which is 

 the reverse of the condition in the case of bicarbonate. The 

 total isohydric shift of chloride amounts to about two thirds 

 that of base under the same conditions. 



On plotting the serum bicarbonate against the serum chlorides 

 it was found that they have a linear relationship, in the case of 

 both oxygenated and of reduced blood, and that an increase in 

 the concentration of bicarbonate in the serum is accompanied by a 

 decrease of chlorides, corresponding to somewhat more than one 

 half of the increase of bicarbonate. These curves appear to be 

 straight lines, and are apparently parallel, indicating a constant 

 difference between oxygenated and reduced blood at all hydrogen 

 ion concentrations. This constant difference, accompanying 

 the change in the state of hemoglobin, and not dependent on the 

 change in concentration of bicarbonate, we are inclined to attribute 

 to the change known to occur in the relative volumes of the red 

 cells and serum. Of the total shift of chlorides at an isohydric 

 point, this constant difference makes up only a small part. 



Since the shift of chlorides, from or to the cells, accounts for 



1 L. J. Henderson, "The Equilibrium between Oxygen and Carbonic Acid in 

 Blood," J. Biol. Chan., 1920, XLI, 401. 



