78 SMELL, TASTE, ALLIED SENSES 



Amyl acetate with no acetic odor but well marked pine- 

 apple flavor. 



Ethyl acetate and amyl acetate have entirely distinct 

 odors, but when propyl acetate and butyl acetate are 

 taken into consideration the four compounds form a se- 

 ries in which there is a transition in odors corresponding 



Table V. 



X 



Estimated potencies of alcohols, Passy (1892c). 



Alcohol Estimated Potency 



Methyl 1 



Ethyl 4 



Propyl 100 



Butyl 1000 



Amyl 10000 



to the changes in chemical structure. Other series of 

 homologues, however, such as the one tested by Huyer 

 (1917), analine, o-, m-, and p-toluidine, xylidine, and cu- 

 mioline, show no such relations. 



Not a few investigators have suggested that the odors 

 of many substances depend upon the number and ar- 

 rangement of certain chemical radicals contained within 

 the odorous molecule. Such radicals are commonly 

 called osmophoric groups. Perhaps one of the most 

 considerable studies of this kind was that carried out by 

 Cohn (1904), but without commensurate results. The 

 most recent and ambitious of these attempts is by Hen- 

 ning (1916) whose classification of odors has already been 

 referred to. 



Henning's studies on the relations of odors to chemical 

 constitution have to do almost entirely with the aromatic 

 compounds, though there is no reason to believe that his 

 generalizations, if true, may not be extended eventually 



