KAHLENBERG — ACTION OF SOLUTIONS ON TASTE. 19 



It is well known that solutions of salts of strong bases with 

 Yerv weak acids have an alkaline reaction toward indicators. This 

 is due to the fact that, these salts are to a certain extent hydro- 

 ly tit-ally decomposed by the water into free acid and caustic al- 

 kali, the latter yielding OH ions by electrolytic dissociation. As 

 examples of salts whose solutions possess alkaline reactions and 

 tastes because of the OH ions due to hydrolytic dissociation 

 may be mentioned the carbonates, silicates, and borates of the 

 alkalies, and the soaps. The fact that the latter In strong so- 

 lutions produce vomiting- is well known; probably this effect is 

 due to the OH ions present in the solution-. 



The taste that a dilute solution containing OH ions causes 

 is difficult to describe. Some of the persons tested said it was 

 a soft, smooth sensation quite unlike that produced by other sub- 

 stances. It would seem somewhat peculiar perhaps that the 

 taste of hydroxy 1 ions, being not sharp like sour or salty tastes, 

 should manifest itself in solutions containing only one gram ion 

 (i. e., 17 grams of OH) in 400 liters. It must be remembered 

 in this connection that hvdroxvl ions, like hydrogen ions, are 

 generally speaking very reactive. What the nature of the ac- 

 tion of the OH ions on the protoplasm of the nerve is, is not 

 known. The mobility of OH ions is very great (being second 

 only to that of II ions as already pointed out), consequently we 

 should expect them to find little difficulty in reaching the nerve 

 endings. 



Water itself is slightly dissociated into hydrogen, and hydroxy! 

 ions. The degree of this dissociation is, however, exceedingly 

 small. Very pure water has been prepared by Kohlrausch, the 

 electrical conductivity of which showed that there were no more 

 than 18 grams of dissociated water present in eleven million li- 

 ters. It is clear that this is far beyond the limit at which H 

 and OH ions can be detected by the sense of taste. It is not 

 very difficult to obtain distilled water of a specific conductivity 

 of 2xl0~ 6 and such water is devoid of taste. If we inquire as 

 to the reason for this, we should agree that the undissociated 

 molecule of water is tasteless because it does not react chemically 



