424 



It has been this comparative constancy in the oils of identical species that 

 has enabled the somewhat extensive trade in Eucalyptus oils from naturally 

 growing trees to have been built up. Had it been otherwise there could 

 hardly have been the desired constancy in the commercial article, nor could 

 necessary standards for control have been arranged. 



In order to illustrate this constancy in general characters from com- 

 mercially collected material, the three tables below are given. The three species 

 chosen are to be considered as types of groups, and all are now extensively 

 utilised for oil production in New South Wales and Victoria. 



The oils to which the figures refer were in these cases distilled for market, 

 and forwarded to the Museum for investigation. There is not the slightest 

 doubt, however, with the specimens tabulated, as to the botanical identity of 

 the species from which the oils had been distilled. It will be noticed that 

 the dates of the distillations extend over several years. 



Space will only permit the tabulation of a few of the results, but they are 

 sufficient to show the small range of variation in the chemical constituents likely 

 to be observed in commercially distilled Eucalyptus oils when from one species 

 only. Similar data from other species might equally well have been given, if 

 thought necessaiy, as, for instance, with the perfumery oils E. Macarthuri, 

 E. citriodora, &c., but a perusal of the results recorded in this work, under the 

 seveial species, will supply abundant evidence of this comparative constancy 

 of their oil products. 



The figures quoted are those published by one of us in the Journal of the 

 Society of Chemical Industry, August, 1918, in a paper prepared to illustrate 

 the value of the Refractometer for determinative purposes, but they may be 

 equally well applied in the present connection. 



(i) EUCALYPTUS POLYBRACTEA (a species distilled in both New South 



Wales and Victoria). 



It will be seen that only two oils listed were laevo-rotatory. This is due 

 to the influence of a small quantity of the optically active aromatic aldehyde 

 aromadendral, and indicates that the distillation of the leaves had been extended 



