100 



CHEMICAL STATICS 



saturated with globulin contain only half the proportion of base 

 to protein which is contained in those which are neutral to phenol- 

 phthalein. Hardy has suggested, in explanation of this, that 

 globulin has at least two replaceable hydrogens and that its acid 

 salts of sodium or potassium are soluble, while its acid salt of 

 barium is relatively insoluble, the " neutral " salt being soluble 

 and neutral to phenolphthalein. Since complete solution of the 

 globulin is just attained at neutrality to litmus and the ratio 

 of the alkali-binding capacity of serum at neutrality to phenol- 

 phthalein to its capacity at neutrality to litmus is 2:1, this 

 hypothesis, although based only upon results obtained with arbi- 

 trarily chosen indicators, would appear to be justifiable. We 

 shall have occasion to further discuss this question from a some- 

 what different point of view in Chap. IX. 



Employing the potentiometric method (37) I have determined 

 the quantity of alkali neutralized by globulin in solutions contain- 

 ing an excess of KOH. The following were the results obtained, 

 the concentration of globulin in each solution being 0.208 per cent. 



The alkali-equivalent of the globulin, therefore, remained appreci- 

 ably constant throughout the range of alkalinities mentioned. Its 

 mean value is 47 X 10~^ gram-equivalents of KOH per gram 

 of globulin, which may therefore be regarded as the alkali-equiva- 

 lent of globulin in the presence of excess of base. 



The ratio of the alkali to the acid-equivalent of globulin at 

 "saturation" is, according to Hardy's determinations 10 : 18. He 

 considers that the true ratio is probably 1 : 2. 



The compounds of globulin with salts have been studied by 

 Hardy (15) and by Mellanby (25). But as these compounds have 

 not yet been clearly defined, and their discussion involves a con- 

 sideration of the general nature of the mechanism of the solution 

 and precipitation of protein by salts, the description of the results 

 obtained by these observers will be deferred to the succeeding 

 chapter. 



