ODORS AND THE SENSE OF SMELL. 683 



acetic and benzoic acids, which, can unite with bases and form 

 salts ; and the ethers, the results of the association of alcohols, 

 acids, or other alcohols, among which are the oils of the onion and 

 of mustard. Among quaternary compounds we have the alkaloids 

 formed by the union of the alcohols with ammonia or other alka- 

 lies, amides formed by the union of ammonia and acids with the 

 separation of the elements of water; and the metallic radical 

 compounds which are obtained by the reaction of metals on some 

 of the ethers. 



Perfumes are, in general, binary or ternary compounds char- 

 acterized by the fact that the proportion of equivalents of hydro- 

 gen to those of carbon diminishes at the same rate as those of an- 

 other class of products very rich in hydrogen which are called the 

 fatty series, while this class of products, less rich in hydrogen, is 

 called the aromatic series. Is there any relation between odor and 

 chemical composition ? An English physiologist, Mr. John Berry 

 Hay craft, in his studies of the savors and odors, and savors of the 

 principal compounds of each natural family of bodies, particular- 

 ly of compounds of the family oxygen, sulphur, chromium, sele- 

 nium, molybdenum, tellurium, didymium, tungsten, and uranium, 

 has observed modifications in odor corresponding with increase in 

 atomic weights. For example, sulphureted hydrogen, hydrogen 

 selenide, and hydrogen telluride smell like rotten eggs. The com- 

 pounds of elements of this family with methyl and ethyl have an 

 alliaceous odor. So with the family chlorine, bromine, and io- 

 dine ; the acids which these bodies form with hydrogen and their 

 compounds with methyl, ethyl, and ethylene have similar odors, 

 so that some among them seem to share them with their neigh- 

 bors ; bromof orm, for example, having a similar odor with chloro- 

 form and iodoform. Passing to the organic series, Mr. Haycraft 

 observes in the monatomic alcohols a modification of odor corre- 

 sponding with variations in atomic weight. Methyl alcohol, for 

 instance, has a weak odor of alcohol ; ethyl alcohol has the typical 

 alcoholic odor ; propylic alcohol has both an alcoholic odor and 

 a special smell; isobutylic, amylic, and octylic alcohols pro- 

 gressively lose the alcoholic odor and acquire as against it a spe- 

 cial scent. The same facts are remarked in the fatty acids and 

 hydrocarbons. 



Similar odors may be furnished by bodies without likeness in 

 chemical composition. Arsenic in oxidizing disengages vapors 

 that have the odor of garlic. Nitrobenzene, benzoic aldehyde, 

 and prussic acid smell much alike. It has been asserted that 

 emeralds pounded and ground several hours a day for three weeks 

 had emitted a well-defined odor of violets. The fact has been 

 verified ; but it has yet to be determined whether it is due to the 

 manipulation or to organic substances that have been released by 



