460 ACTION OF ACID AND ALKALI ON GLUTEN 



making. Accordingly the measurements have in some respects not 

 been pushed to the highest possible accuracy, nor has every part of 

 the question been carefully surveyed. 



I. 



The first part of the work consisted of measurements, with the con- 

 centration cell, of the hydrogen ion concentration of solutions which 

 had been in contact with powdered gluten. 



The data in Table I show that, as a first approximation, the hydro- 

 gen ion concentration in such systems is determined by the ratio of 

 gluten to acid, or gluten to base. In the acid systems this is quite 

 clear; in the alkaline systems, where unknown difficulties have inter- 

 fered with the accuracy of the measurements, it is perhaps somewhat 

 less apparent. But, in view of the fact that under the circumstances 

 equilibrium can hardly be perfectly attained, and on account of the 

 numerous other difficulties which are inherent in work of this kind, 

 the evidence seems satisfactory. 



This result accords with the work of Sorensen. But the system that 

 we have studied contains large amounts of protein in a discrete phase, 

 and frequently also large amounts dispersed throughout the aqueous 

 solution, and therefore possesses a very high degree of complexity. 

 It is on this account especially important that the simple relationship 

 still holds good. Unpublished measurements upon purified glutenin 

 and gliadin further confirm this observation. Therefore we venture 

 to draw the conclusion that' in systems containing gluten and acids or 

 bases the formation of salts, in accordance with the requirements of 

 the mass law, is the fundamental phenomenon. Here, as in all cases 

 where a weak acid or base in excess is in equilibrium with a strong base 

 or acid, the hydrogen ion concentration is dependent upon the ratio 

 of acid to salt or of salt to base, as the case may be. This relation- 

 ship is of course only approximate, less true in the neighborhood of 

 the isoelectric point. Compared with the case of simple substances, 

 it is modified in a definite and characteristic manner by the polybasic 

 and polyacid character of the amphoteric protein. It is not, however, 

 seriously modified by the heterogenity of the system or by the col- 

 loidal character of the protein. This subject will be discussed theo- 

 retically in a later paper. 



