DETERMINATION OF ACIDITY AND ALKALINITY 109 



Upon the addition of an amount dA of CO2 we have 



dpH 1 



— — = - (log e) - 



dA A 



By making use of the definitions given above, we may designate 

 the ratio of the decrease of CO2 to the increase in pH as the "special 



buffer effect" of the mixture, v', which becomes simply v' = + -r-, 



or, in terms of the reciprocal value, the "special buffer value," N', 



N' = A ■ 



The "special buffer effect" of a buffer mixture consisting of CO2 

 + NaHCOz is therefore independent of the concentration of the bicar- 

 bonate and is inversely proportional to the concentration of the carbon 

 dioxide. 



This remarkable law expresses a mode of defense of the living 

 organism against changes in pH which might be caused by the 

 increase of CO2. Augmentation of CO2 in the blood sets in motion 

 the automatic processes which lead to the elimination of the CO2 

 present in excess. But should these automatic processes temporarily 

 fail because of an excessive strain upon them, then the accumulation 

 of CO2 in the blood results in a progressively decreasing change in pH. 

 It will be shown later that in acidosis there is a smaller concentration 

 of free CO2 in the blood than normally. The "special buffer effect" 

 of such blood is considerably below the normal value, or in other 

 words, the acidotic blood is more poorly buffered than normal blood. 

 The same amount of CO2 arising in the metabolism changes the pH 

 of the acidotic blood more than it would the pH of normal blood. 

 The irritation produced by a given amount of CO2 in all regulatory 

 centers controlled by the pH of the blood, is greater in acidosis than 

 in the normal state. ^^ 



" Simultaneously with the publication of the second German edition of this 

 book there appeared an article by Van Slyke (D. D. Van Slyke, Journ. Biol. 

 Chem., 52, 525, (1922)) in which the theory of buffers was treated on the same 

 basis but much more thoroughly. For further study of this problem this 

 article is especially recommended. 



