92 POPULAR SCIENCE MONTHLY. 



that some may be found among them the odors of which can be 

 utilized. 



Syntheses of this kind only rarely lead to natural principles; 

 more frequently what perfumers call chemical products are obtained, 

 or perfumes which betray their origin to a greater or less extent, 

 and can not be used in the preparation of the finest products, but 

 have cheapness and great strength in their favor. We should observe 

 that chemical synthesis takes to the odorous principle itself, while 

 essences contain only a very slight proportion of the active substance. 



Finally, it sometimes happens that no new material is discov- 

 ered, but some laboratory reaction already known is turned to indus- 

 trial use. Such is the case with heliotropine, formerly known as 

 piperonylic aldehyde or piperonal; terpineol, or white lilac; anisic 

 aldehyde, or hawthorn, etc. 



Twenty-five or thirty years ago it was believed that with a few 

 well-known exceptions, such as those of bitter almonds, anise, mus- 

 tard, and some others, the essences were constituted of hydrocarbons, 

 CioHi 6 in indefinite numbers, all isomeric and similar to spirits of 

 turpentine. Our views on this subject have been considerably modi- 

 fied. It has been found that the hydrocarbons or terpenes contained 

 in essences may be referred to well-defined species possessing charac- 

 teristic reactions and derivatives, some of them crystallizable, by 

 which they may be distinguished. Oxidized principles have been 

 isolated in essences related to the fatty series, capable of facile trans- 

 formation into cyclic derivatives, which may be regarded as con- 

 necting links between the fatty and the aromatic series. Frequently 

 a natural essence represents a harmonious mixture of various com- 

 binations. Oil of bergamot, having a composition of this character, 

 possesses an odor vastly more characteristic than any of its components 

 taken separately. And it sometimes happens that compounds suit- 

 able for fine perfumery, if they were pure, are spoiled by the pres- 

 ence of disagreeably smelling substances. The elimination of such 

 principles, or the refining of such perfumes, has given rise to a 

 second branch of our chemical industry. 



The discoveries that have so far been made are quite insufficient 

 to explain the composition and odor of essences. We find certain 

 substances, like linalool and geraniol, common constituents in es- 

 sences of the most different characters, and are hence forced to recog- 

 nize that in a great number of cases they are only the vehicle, the 

 substratum, of the really characteristic perfume; and we begin to 

 suspect the presence of still rarer principles corresponding probably 

 with a more differentiated, more specialized organism, and related to 

 the specific characteristics of the vegetable cell. — Translated for 

 the Popular Science Monthly from the Revue Scientiftque. 



