98 



The Effect of Sugar on Sourness. 



p. N. Evans. 



It is common experience that some foods and beverages taste less sour 

 when sugar is added, and it seems worth while to seek an explanation of 

 the fact. 



In books of popular science the statement is sometimes made that 

 the sugar "neutralizes" the acid — in some such way, presumajjly, as a base 

 might- This explanation is untenable from the chemist's standpoint, in- 

 asmuch as sugar enters into no such reaction with acids. 



Better informed writers sometimes aver that since sugar can not neu- 

 tralize acids its value in such cases is onlj- imaginary and not real. Since, 

 nowever, in matters of taste, if the imagination is satisfied the problem is 

 practically solved, it becomes of interest to know how the imagination is 

 satisfied in this instance. 



Sourness is now ]vno\^ll to l)e a property of the hydrogen ion; for all 

 acids, and acids only, are sour, and all have this constituent, and this only, 

 in common, when dissolved in water. A diminution in intensity of sour- 

 ness must therefore be due either to a reduction in the number of hydrogen 

 ions in a given volume of the solution, or to a lessened sensitiveness to 

 sourness on the part of the nerves of taste. 



An investigation was made by the writer as to whether the introduction 

 of sugar diminished the degree of ionization of hydrochloric acid in a given 

 solution, using the freezing point method, and it was found that there was 

 no effect, the degree of ionization of the acid being the same in the pres- 

 ence and in the absence of sugar. 



The value of sugar, then, must depend on its physiological effect on 

 the nerves of taste, not on any chemical action by which the concentration 

 of hydrogen ions is reduced. 



Some ye.'irs ago Professor T. W. Richards of Harvard Oniversity (Am. 

 Chem. Jour. ISOS, 121), called attention to the delicacy of the sense of taste 

 in detecting sourness and in comparing it in different intensities. With the 

 assistance of Miss Carrie Richardson (now Mrs. C. E. Roth) the writer 



