CARBONIC ACID 159 



HA + NaHC0 3 = NaA + II 2 C0 3 



This reaction corresponds exactly to the 

 simple case first discussed, and so causes an 

 inconsiderable change in the concentration of 

 ionized hydrogen. The free carbonic acid 

 then passes out through the lungs, and the 

 salt is excreted in the urine. Other processes 

 are involved, including a device for final re- 

 tention of a part of the alkali which has neutral- 

 ized acid, 1 but in the whole complex function 

 nothing is more important than the simple 

 reaction written above. 



The hydrogen ion concentration exerts a 

 marked influence upon the rate of progress 

 of chemical reactions. Thus, for example, 

 the so-called inversion of cane sugar by a proc- 

 ess of hydrolytic cleavage into glucose and 

 fructose, 



C12H22OH + H 2 = C 6 H 12 6 + C 6 H 12 6 , 



is commonly accomplished by warming a solu- 

 tion of sugar to which a little acid has been 

 added. It was shown by the classical investi- 

 gation of Wilhelmi that the velocity of this 

 process depends upon the strength of the 

 acid, or, according to the modern view, upon 



1 Henderson, Journal of Biological Chemistry, IX, 403, 

 1911. 



