AMYL ESTER OF EUDESMIC ACID IN EUCALYPTUS OILS. / 6 



Eucalyptus aggregata, contains the ester in sufficient quantity to 

 enable its constituents to be isolated and determined. 



Unfortunately the yield of oil is small in those species of 

 Eucalyptus giving this ester in largest amount. The leaves of the 

 "Black Gruin"i?. aggregata, from which this oil was obtained, 

 were sent by the Museum collector, Mr. Bauerlen, in the month 

 of October, from Fagan's Creek, near Braidwood, in this colony. 

 Four hundred pounds of leaves were received, but the amount of 

 oil obtained was only two and a half ounces, equal to 004 per cent. 

 More material was not obtainable later, without great trouble and 

 expense, as trees of this species do not occur within easy distance 

 of Sydney. More leaves of the " Black Gum " will be obtained at 

 the first opportunity and the chemistry of the acid completed, a 

 research I would like to reserve to myself. 



It is probable, however, that we may yet find other species of 

 Eucalyptus containing this ester in fairly large quantities. The 

 oils of E. botryoides and of E. saligna contain an ester in fair 

 amount ; it is present in the oil of E. rostrata, and in the oils of 

 several other species its presence can be proved. 



The determination of this ester explains much in reference to 

 Eucalyptus oil that previously seemed obscure. It is most prob- 

 able that the amyl alcohol of this ester is connected with the 

 valeraldehyde known to be present in these oils, and it may, 

 perhaps, be found eventually, that the (?) cuminaldehyde, existing 

 in so many of these Eucalyptus oils, has some connection with the 

 acid of the ester. In the oil of E. rostrata both the ester and 

 (1) cuminaldehyde occur together. The presence of this aldehyde 

 is much more frequent in these oils than was previously supposed. 



[Since this paper was prepared I have been investigating the 

 aromatic aldehyde found in many Eucalyptus oils. This con- 

 stituent was previously supposed to be cuminaldehyde and its 

 odour and reactions certainly suggested that substance ; but 

 further research points to the fact that it is not ordinary cumin- 

 aldehyde. When isolated in a pure condition its odour is more 



