KAHLENBERG — ACTION OP SOLUTIONS ON TASTE. 17 



no doubt they do especially in strong solutions, and to these 

 effects the differences of the individual solutions are due. 



It is well known that solutions of most of the salts of the heavy 

 metals have acid reactions and that they have an astringent ef- 

 fect upon the membranes of the mouth, besides creating in some 

 cases the so-called metallic taste. The solutions of all of these 

 salts contain hydrogen ions whose presence is caused by hydro- 

 lytic dissociation as in the case of the salts of iron and alumi- 

 num. To these hydrogen ions the astringent effect of the solu- 

 tions is very likely to be ascribed in many cases. Salts of 

 stronger acids with the alkalies are not decomposed hydrolyti- 

 cally and do not possess astringent properties. Long 1 used the 

 method of sugar inversion in investigating the hydrolytic decom- 

 position of salt solutions. He employed a polariscope in his 

 work and consequently could test only colorless solutions. The 

 freezing- and boiling-point methods, however, can be used quite 

 as well as the polariscope in this work; although by means of 

 them the observations are perhaps not quite as accurately and 

 readily made. They possess the advantage, however, that they 

 can be used with colored solutions. Experiments along this line 

 have for some time been in progress in this laboratory and the 

 results will soon be ready for publication. 



As to the nature of the chemical action of the hydrogen ions 

 on the nerve nothing definite is known, indeed the same must 

 be said of the action of any ingredient on the nerves of taste. 

 It is significant, however, that hydrogen ions can be detected 

 by the sense of taste in very dilute solutions, the limit being 

 in the neighborhood of ^, or one gram of hydrogen ions in 

 800,000 grams of water. The speed of migration of the hydrogen 

 ion exceeds that of any other ion; it is about one and three- 

 fourths times that of the next fastest ion, the hydroxyl ion. In- 

 timatelv connected with this is the fact that solutions of strong 

 acids diffuse more rapidly than those of their salts. By virtue 

 of their great mobility, it is clear that hydrogen ions can easily 



UjOC. Cit. 



