292 EUCALYPTUS. 



Phellandrene . This is one of the several free terpenes represented 

 by the formula Cio Hi6. It is capable of existing in two optical modifi- 

 cations, one turning the plane of polarized light to the left and the other 

 to the right. It boils at about 170 degrees. 



With many writers on Eucalyptus Oils, it is a veritable pariah 

 amongst terpenes, its presence disqualifying a Eucalyptus Oil. Those 

 who object to its presence look upon it as a mere diluent of Eucalyptus 

 Oil, stating that it possesses no medicinal properties that are not pos- 

 sessed by the terpenes of the cheaper oil of turpentine. At the same 

 time we have no direct evidence that the terpene phellandrene is not a 

 therapeutically active constituent of Eucalyptus Oil. In some it is en- 

 tirely absent, in most it exists in greater or less quantity. It my be readily 

 detected in an oil if treated with a concentrated solution of sodium ni- 

 trate. If a few drops of glacial acetic acid be added to the mixture a 

 copious formation of crystals of phellandrene nitrate (of a whitish color) 

 ensues, 



Aldehydes. The pungent and irritating odor of the oils of some 

 species is owing to the presence of aldehydes, and fortunately there is no 

 real difficulty in removing them by rectification. These cough-producing 

 substances should always be removed, and I have heard a curious reason 

 why manufacturers retain them in some oils. It is that the public like a 

 pronounced flavor; some "fire in the oil," in fact. But I hope that the 

 taste of the public will become enlightened, for these aldehydes may 

 cause most serious results in persons suffering from throat, bronchial, or 

 lung troubles, while I know of no compensating value whatever. 



At the same time there are some sweet-scented and non-injurious 

 aldehydes, e. g., citronellon, which forms so large a proportion of the oil 

 of E. maculata^ var. citriodora. 



Various Eucalyptus oils contain other other constituents, but they 

 are of minor importance. 



