214 



ELECTROCHEMISTRY 



have to add 400 X 10~^ equivalents of HCl to reach an acidity 

 of 0.5 X 10"^ equivalents — just over one-tenth of a per cent of 

 the acid added. Were the casein present in a concentration of 

 8 per cent (the 'percentage concentration of the proteins in the 

 blood), 3200 X 10-5 gram equivalents of HCl, or 320 cc. of a 

 tenth normal solution, would have to be added to a litre of the 

 solution to attain an acidity of 0.5 X 10"^ equivalents. One 

 twentieth of a cubic centimeter of tenth normal HCl, added to a 

 litre of pure distilled water, would produce the same acidity. The 

 power of the proteins to maintain the neutrality of the fluids in 

 which they occur is therefore very remarkable, and Loeb (36), 

 myself (55) (56) (57) (58) and others have suggested that they 

 play an important part in regulating the neutrality of the tissues 

 and tissue-fluids, while Hoppe-Seyler (32), Sertoli (65), Zuntz (72) 

 (73) and myself (55) (57) have advanced the view that the liber- 

 ation of CO2 from the blood in the lungs is accompanied by a 

 transport of sodium from the carbonic acid to the proteins of the 

 plasma. 



Friedenthal (19) (20), Spiro (68), Loeb (36) and Henderson 

 (27) (28) (29) (30) have pointed out that the bicarbonates of the 

 blood and other media in which organisms live must also be of 

 importance in preserving their neutrality. Henderson points out 

 that the rate of change in the alkalinity or acidity of a solution 

 of an acid is a minimum when the dissociation constant of the 

 acid is equal to the hydrogen ion concentration (8 X 10"^ N) at 

 neutrality. He illustrates this by the following table, showing 

 the amount of tenth normal alkali required to secure a definite 

 but arbitrarily chosen change in alkalinity when added to equal 

 amounts of the undermentioned acids. 



Henderson believes that the neutrality of the tissue fluids is 

 chiefly maintained by the bicarbonates which they contain 



