286 H. G. SMITH. 



On a NEW AROMATIC ALDEHYDE OCCURRING in 



EUCALYPTUS OILS. 



By Henry G. Smith, f.c.s., Assistant Curator, Technological 



Museum, Sydney. 



[Read before the Royal Society of N. 8. Wales, December 5, 1900.'] 



In a paper read before this Society in June of this year, 1 the an- 

 nouncement was made that the aldehyde occurring in Eucalyptus 

 oils, and which for a long time had been supposed to be cuminalde- 

 hyde, was most probably not that subslance, the reasons, then 

 available for that conclusion, being given. I was induced to 

 investigate this subject because it was found that this aldehyde 

 occurs in a very large number of Eucalyptus oils in varying 

 amounts, and is probably present in the majority of them. 



In the oils obtained from the true "boxes," Eucalyptus hemi- 

 phloia, E. albens, E. Woollsiana, etc., this constituent occurs in 

 greatest amount, and if we take E. hemiphloia as the extreme end 

 of the list of those species in which this aldehyde occurs most 

 plentifully, we can descend the scale through the "boxes" into 

 the "gums," and so onward to those species the oils of which 

 contain the greatest quantity of eucalyptol or cineol. 



From the results of this research this appears to be quite feasible, 

 as it is probable that the natural eucalyptol in Eucalyptus oils is 

 derived directly or indirectly from this aldehyde, and we may 

 assume that it will eventually be proven that the yellowish tint 

 in Eucalyptus oils of the better class, or those richest in eucalyptol, 

 is due to the original presence of this aldehyde, as the oils con- 

 taining this aldehyde when rectified are all more or less yellow, 

 and are generally not rich in eucalyptol. Oils very rich in phel- 

 landrene, such as E. dives, E. radiata, etc., do not appear to contain 

 this aldehyde, it being replaced in those oils by the ketone of 

 peppermint odour, consequently these oils are generally almost 



1 On the amyl ester of eudesmic acid occurring in Eucalyptus oils, p. 72. 



