200 Proceedings of the Royal Society of Victoria. 



are of low density and Ifevo-rotatory, though some few that are 

 Isevo-rotatory do not give the Phellandrene reaction. 



These results are in harmony with the general conclusions so 

 tar obtained in the study of the chemistry of the Eucalyptus- 

 Oils, the chief result of which is to show that these oils contain 

 two main ingredients of different densities, rotation and specific 

 refractive energies ; difierences in the proportion of the ingredients 

 producing such differences as are recorded in the tables. The 

 researches of Wallach {Ann. der Chem., 225 et seq.; Ber der 

 Deut. Chem. Ges., 24) have established that the two main 

 ingredients are a Terpene or mixture of closely related Tei-penes 

 CioHig, and Cineol (Eucalyptol) CioHi.sO- The values of 

 the above physical constants for some of these Terpenes and 

 Cineol are approximately as follow, the values of different 

 authorities varying too much to allow of any but approximate 

 values being given : — • 



Table IV. 



The range of density -848 to •927 corresponds closely to that 

 pointed out as holding in the natural Eucalyptus-Oils, namely 

 •853 to -933, and the range of specific refractive energy is -495 to 

 •562, to be compared with the range "49 to -56 of the natural 

 oils. Thus it is quite clear that in the Eucalyptus-Oils as a 

 whole we have to do with mixtures in varying proportions of 

 bodies of the two types, Cineol C^oHigO and Terpene C^qHi,;. 



To determine which of the many isomerides possible for both 

 of these types are really present in any one oil, the methods of 

 investigation developed by Wallach will have to be applied ; but 

 at present it can be seen that the values of physical constants 

 give a good measure of the relative proportions of the ingredients 

 CioHigOand CjoHifi. 



