ESSENTIAL OILS. 81 



the leaves of this tree is richer in the aldehyde citronellal than that 

 of any other known plant, and its physical and chemical characters 

 are remarkably constant, no matter where the trees are grown. 

 This is, of course, only what is to be expected with identical species 

 of Myrtaceous plants. The yield of oil varies from 0-6 to 0-9 per 

 cent., and this result has been obtained commercially from many 

 tons of leaves and terminal branchlets. The oil is distinctly 

 aromatic, has a pleasant citronellal-like odour, and is much used 

 as a perfume for soap, for which purpose it is admirably suited. 

 A sample of oil freshly distilled in Queensland was analysed early 

 in 1910 and gave — 



Specific gravity at 21°C = 0-8652. 



Optical rotation «,) .. .. .. =-fl-7'^ 



Refractive index at 22°C = 1-4542. 



Aldehydes = 920o- 



Soluble in Ij volumes 70% alcohol by weight. 



This agrees very well with the results obtained with the oil of a 

 cultivated tree grown at Sydney. Eucalyptol and phellandrene 

 are both absent in the oil of this species. 



The trade in the grass citronella oils is an extensive one, and 

 in 1909 the exports of this oil from Ceylon were about l.llO.OCO lb. 

 the value being about one shilling per lb. The oil of E. citriodora 

 when distilled from material collected from large trees, as at 

 present, cannot be produced at so low a price, but by systematic 

 cultivation there seems no reason why this should not be done, 

 and if the industry were on a sufficiently extensive scale the oil 

 might be prepared at a considerably cheaper rate than is possible 

 at the present time. With an equal competition in price there 

 seems no reason why much of the trade in citronella oils should 

 not be appropriated by Australia, and distilled from the leaves 

 of this .species of Eucalyptus. 



4. — Eucalyptol (Cineol) Oils. 



Eucalyptus oils richest in Eucalyptol are in most countries 

 official, and to pass the tests demanded by their pharmacopoeias 

 it is necessary that more than half the whole oil should consist of that 

 constituent. It is not appropriate here to consider the relative 

 medicinal value of the various constituents found in Eucalyptus oils 

 so far as experiments have gone, but it is very probable that 

 Eucalyptol will be found eventually not to be the most efficacious 

 in this direction. From a commercial point of view it is sufficient 

 that Eucalyptol Eucalyptus oils are demanded for pharmaceutical 

 purposes, and as the world's requirements for eucalyptus oil of this 

 class are now somewhat considerable, the production to meet this 

 demand is one of some importance. Eucalyptol is perhaps the 

 most frequent constituent in the oils of the Eucalypts and Mela- 

 leucas, but varies in quantity in the oils of the various species, so 



