366 



SUMMARY OF METHODS. 



The foregoing may be summarised as follows : 



i. That an accurate method for determining the amount of cineol in 

 Eucalyptus oils under all conditions has yet to be discovered. 



2. That no one present method is applicable in all cases. 



3. That arsenic acid is less advantageous for the purpose than phos- 



phoric acid. 



4. That the use of petroleum ether in connection with phosphoric acid 



is an advantage if the process be carried out in the manner 

 directed. 



5. That the richest cineol Eucalyptus oils should be diluted with 



non-cineol containing terpenes, corrections being made for the 

 dilution. 



6. That the resorcinol method is only applicable with certain oils, such 



as those containing cineol in the greatest amount, or those, in which 

 it occurs in too small quantity to be determined with phosphoric 

 acid. Constituents absorbable by resorcinol, other than cineol, are 

 too abundant in Eucalyptus oils for this method to be of general 

 application, although it has certain advantages for experimental 

 work . 



7. The process recommended for the purpose, in Australia particularly, 



is the rapid phosphoric acid method, using petroleum ether in order 

 to remove the non-cineol bodies before pressing. 



Gcraniol and its Acetic Acid Ester Occurring 



in Eucalyptus Oils. 



The alcohol geraniol and its acetic acid ester are frequently occurring con- 

 stituents in Australian plants, and in the oils of no less than three species 

 does geranyl-acetate occur to the extent of 60 per cent, or over. 



The coniferous tree Callitris Tasmanica, the "Oyster Bay Pine" of Tas- 

 mania, yields an oil of this character (Research on the Pines of Australia, Baker 

 and Smith, Technical Education Series, N.S.W., No. 16, page -'40 , while the 

 others belong to the Myrtacese. One of these is Darwiuia fascicularis, a shrub 

 growing around the shores of Port Jackson, New South Wales (Proc. Roy. Soc, 

 N.S.W., December, 1899), while the other, Eucalyptus Macavthuri . is a fine 

 foliaceous tree which grows plentifully in the Wingello and neighbouring districts 

 of New South Wales (Proc. Roy. Soc, N.S.W., November, 1900). In lesser 

 amounts this ester occurs in the oils of numerous species of Eucalyptus. 



Geranyl-acetate is also the chief ester in the oils of the Angophoras, a genus 

 closelv related to Eucalyptus, and perhaps the older. If this is so then most 

 likely the ester passed into Eucalyptus through Angophora, and as it occurs also 

 in the oils of many of the " Peppermints " it probably runs through the whole 

 genus Eucalyptus, although in some of the oils the amount is very small. 



Eucalyptus Macavthuri, similarly with other species of Eucalyptus, shows 

 a comparative constancy in oil products. That this is so has been well demon- 

 strated from the results of much work carried out with this species during recent 

 years. We have recorded some of this data under the species in this 

 publication. 



