BIOLOGICAL APPLICATIONS 215 



and in a minor degree by the phosphates and by the proteins. 

 He illustrates his hypothesis by reference to a system tenth- 

 molecular in total carbonic acid and equally concentrated in 

 total phosphoric acid, combined or uncombined with sodium, 

 and he shows that in order to appreciably change the acidity of 

 this system a quantity of acid comparable with the total amount 

 of sodium which is present at neutrality must be added. He 

 estimates, from known quantitative data, the quantity of acid 

 which would be neutralized by the bicarbonates of the blood in 

 passing from the reaction of normal blood (= 0.37 X 10^'^ H+ at 

 38 degrees) to that of blood in advanced acid intoxication (about 

 1.00 X 10"'' H+ at 38 degrees). At the same time, from data 

 derived from experiments in which he employed indicators to 

 determine the change in the reaction of solutions of the serum- 

 proteins to which varying amounts of acid and alkali had been 

 added, he estimated the amount of acid which is neutralized by 

 the proteins of the blood, and their salts, as the reaction of their 

 solutions changes by the same amount, and he concludes that 

 it cannot be more than one-fifth of the amount of acid which 

 would be neutralized by the bicarbonates. 



Experimental results which involve the use of indicators to 

 determine such slight changes in reaction as these afford an un- 

 satisfactory basis for so important a theoretical conclusion. Ac- 

 cordingly, employing the potentiometric method, I carried out a 

 series of determinations of the reactions of solutions of the pro- 

 teins of serum, of the concentration in which they occur in serum, 

 to which varying amounts of acid or alkali had been added (58). 

 The results of these experiments entirely confirm Henderson's 

 estimate of the neutralizing power of the proteins of blood-serum 

 between the reactions mentioned above. 



The proteins of ox-blood serum were coagulated by alcohol, 

 carefully washed with alcohol and ether and dried. They were 

 then dissolved in 0.01 N KCl containing varying concentrations 

 of KOH or HCl, each solution containing 8 per cent of the pro- 

 teins (= percentage concentration in blood). The following were 

 the results obtained.* 



* The value of K, the constant ionic product for water at 34 degrees, was 

 taken as (1.47 X 10-^)2 = 2.16 X 10"" (Cf. Kohlrausch and HeydweiUer 

 (33)). The experimental error in the determination of Ch+ in the "unknown" 

 is not more than 6 per cent of Ch+. 



