124 H. G. SMITH. 



Note on the SESQUITERPENE of EUCALYPTUS OILS. 

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



Technological Museum. 



[Read before the Royal Society of N. S. Wales, November 6, 1901.'] 



When an Eucalyptus oil is quantitatively determined for 

 eucalyptol with phosphoric acid a pink or reddish colour is usually 

 given to the mixture. This is particularly the case with the oils 

 of higher specific gravity which consist largely of eucalyptol. The 

 •appearance of this reddish colour has often been taken to denote 

 the end reaction for this determination, but the constituent causing 

 it cannot be considered as an indicator for eucalyptol because 

 the greater the proportion of the constituent occurring in a 

 particular oil the sooner the colour will appear. 



The constituent of Eucalyptus oils causing this colour reaction 

 with phosphoric acid is a sesquiterpene, and it probably occurs in 

 varying amount in all the oils of the series. In some of these it 

 occurs in great abundance, and over fifty per cent, of the oil of 

 E. hcemastoma distilled above 225° C, nor, was this an abnormal 

 sample, because material of this species was obtained from locali- 

 ties nearly one hundred and fifty miles apart, and both the 

 •samples of oil were in agreement, indicating that the sesquiterpene 

 follows the general rule with these oils, of identical species of 

 Eucalypts giving practically identical oils irrespective of location. 

 The oils from the following species were also found to contain the 

 sesquiterpene in quantity : — E. eximia, E. nova-anglica, E. trachy- 

 phloia, E. affinis, E. maculata, E. crebra, E. viminalis, and E. 

 acmenoides. It may occur in these oils with either pinene or 

 phellandrene as the principal terpene, and eucalyptol may be 

 either present or absent. There appears to be only one sesqui- 

 terpene in Eucalyptus oils, because the product obtained by 

 fractional distillation (finally over sodium) from the mixed higher 



