SERUM GLOBULIN 



99 



We have already had occasion to discuss the interpretation of simi- 

 lar phenomena which are displayed by the compounds of casein 

 with acids. 



The acid-equivalent of serum-globulin for dibasic (strong) acids 

 is twice that for monobasic acids, and for tribasic (strong) acids 

 it is three times that for monobasic acids. Hence serum-globulin 

 combines with acids, at "saturation" in molecular and not equiva- 

 lent molecular proportions. 



Solutions of acids " saturated" with serum-globulin are faintly 

 acid to methyl orange. 



Employing the potentiometric method (37) (39) I have deter- 

 mined the quantity of acid neutralized by globulin in solutions of 

 hydrochloric acid of various concentrations. The following are 

 among my results, the concentration of globulin in each solution 

 being 0.496 per cent. 



We see that the acid-equivalent of serum-globulin rises with in- 

 creasing acidity of its solution. 



The compounds of serum-globulin with bases have also been 

 investigated by Hardy. He finds that at " saturation " of solutions 

 of bases with serum-globulin the bases are bound by the globulin 

 in molecular, not equivalent molecular proportions. Solutions of 

 monacid bases " saturated" with globulin are neutral to litmus, 

 the alkali equivalent for monacid bases being approximately 

 10 X 10~ 5 gram-equivalents of the base per gram of globulin, that 

 for di-acid bases being approximately 20 X 10~ 5 in the same units. 



At neutrality to phenolphthalein, however, that is, at an alka- 

 linity corresponding to an OH' concentration of 20 X 10~ 7 (Cf. 

 Salm (48)), the bases are bound in equivalent molecular pro- 

 portions, such that one gram of globulin binds 20 X 10~ 5 gram- 

 equivalents of the base. Thus the point of complete saturation of 

 Ba(OH) 2 solutions by globulin and that of neutrality to phenol- 

 phthalein coincide, while solutions of the monacid bases which are 



