140 SMELL, TASTE, ALLIED SENSES 



salty. Other chlorides, such as those of ammonium and 

 magnesium, have a saline taste. 



This taste, however, is not due exclusively to chlorine 

 ions. Sodium bromide at 0.02 molar has a faint saline 

 taste and is unquestionably salty at 0.04. Hence the 

 bromine ion must also be a stimulus for the salty taste. 

 Kahlenberg (1898) reported it as not quite so effective 

 in this respect as the chlorine ion. Although solutions 

 of sodium iodide at 0.04 or even at 0.02 molar could be 

 distinguished from water, they did not give an unques- 

 tionable taste till a concentration of 0.16 was reached. 

 At this concentration the taste w r as markedly saline. A 

 corresponding solution of potassium iodide was found 

 also to be salty though in this instance the taste was ac- 

 companied by a slightly bitter flavor. Prom these con- 

 siderations it is evident that iodine ions are saline stimuli 

 though they are not so effective in this respect as chlorine 

 or bromine ions are. The sulphates of sodium and of 

 potassium as w r ell as their nitrates also have a saltiness 

 in their tastes and it has been shown in these instances 

 that the sulphate and nitrate ions are the effective agents. 

 Thus all saline tastes depend upon ionic stimuli, and, as 

 Kahlenberg (1898) and Hober and Kiesow (1898) have 

 maintained, these ions are always anions, a conclusion 

 supported by the more recent work of Herlitzka (1908). 



6. The Bitter Taste. The bitter taste is character- 

 istic of almost all alkaloids, and of certain unrelated sub- 

 stances such as dextro-mannose, the glucosides, picric 

 acid, ether, and certain inorganic salts such as magnesium 

 sulphate or Epsom salt. 



Magnesium salts when sufficiently concentrated have 

 a bitter taste and this taste is due to the magnesium ion. 

 This is in strong contrast with the ions of sodium and 



