COMBINING CAPACITY 203 



The results are shown graphically in the accompanying figure: 



0.01 



0.005: 



0.01 



- 0.005 



0.01 



0.006 



6i is the concentration of KOH in 

 which 1 per cent ovomucoid is dis- 

 solved; m is the number of gram- 

 equivalents of KOH which is neutral- 

 ized per litre. 



0.005 0.01 



ai is the concentration of HCl in 

 which 1 per cent ovomucoid is dis- 

 solved; m is the number of gram- 

 equivalents of HCl which is neutral- 

 ized per litre. 



It is obvious that the relationship between the amount of 

 acid or base neutralized by the ovomucoid and the total amount 

 of base present is of very much the same general nature as the 

 corresponding relationship for solutions of casein in KOH — 

 solutions. Ovomucoid, however, differs very strikingly from 

 casein in the fact that it is predominantly basic, while casein is 

 predominantly acid. The maximum combining capacity of ovo- 

 mucoid for KOH is obviously about 50 X 10"^ equivalents per 

 gram, but its maximum combining capacity for acids was not 

 attained in any of the solutions investigated and must be at least 

 lOL) X 10~^ equivalents per gram. Since free ovomucoid, unlike 

 free casein, is soluble in water the quantity of a base or acid which 

 enters into one — N.HOC— group cannot be estimated from 

 these data alone, but it is evident that it cannot be in excess of 

 50 X 10-^ per gram of protein. 



The combining capacities of serum albumin, gelatin and de- 

 aminized gelatin for acids have been determined electrometri- 

 cally by Pauli and Hirschfeld (49). They find that, as in the 

 case of casein, the maximum combining capacities of these pro- 

 teins are independent of their dilution and, moreover, that in 

 isohydric solutions acetic acid, despite the fact that it yields a 

 much inferior proportion of hydrogen ions, is bound by proteins 

 in greater proportion than hydrochloric acid, a fact which in 



