The Comparative Constancy of the Oil Products 

 from Individual Species of Eucalyptus. 



THIS question may be considered as one of considerable importance to the 

 distiller, particularly as Eucalyptus trees are so abundant in Australia, the 

 greater portion of the natural vegetation of the country being composed of trees 

 belonging to this genus. 



The leaves of all the Eucalypts are evergreen, so that distillation can 

 proceed throughout the year, but the oil is less in amount during the winter 

 months. Although practically all the species contain an essential oil, yet, 

 with many of them, the yield is very small indeed, and thus they are not 

 profitable to work. (See table of yields in separate list.) 



From a commercial point of view only a small percentage of the species 

 can be utilised for oil production, the principal reasons for such limitation being 

 (i) the constitution of the oil itself, and (2) the variation in- the amounts of oil 

 yielded by the several species. 



The competition for trade among the distillers naturally causes those 

 species which produce the greatest amount of oil per tank,* all else being equal, 

 to be the most in demand, and consequently distillation from material growing 

 naturally can only be carried on profitably in those portions of the country where 

 the desired species abound. It. has been this question of yield that, among 

 the richer cineol-bearing oils, has caused E. globulus to recede in the world's 

 markets from the position it once held, and in Australia to-day only a very 

 small amount of oil is distilled from that species, the reason being that the yield 

 is too small in amount for it to compete satisfactorily with the more profitable 

 Eucalypts, such as E. polybractea, E. Australiana, E. cneorifolia, E. Smithii, &c., 

 all of which furnish rich cineol oils, and give practically double the amount from 

 the same weight of leaf material as from E. globulus. In the case of E. 

 Australiana the yield is three times as great. 



In view of the geographical distribution of the genus in Australia, with 

 an area of 3,000,000 square miles, the number of distinct species is comparatively 

 not great, but their oil products vary much in constitution among themselves, 

 although comparatively constant for individual species. 



The large amount of research which has been carried out during recent 

 years on their oils, has demonstrated quite clearly that a particular Eucalyptus 

 species will produce from average material an oil practically constant in 

 composition and general characters, f and also give a fairly uniform yield, 

 providing the material for distillation has been well selected and not too 

 coarsely cut, or with too many branchlets. 



* In some parts of Australia, New South Wales particularly, the standard upon which payment is made for 



cutting the leaf material, for calculating the contents of the digesters, and the statement of oil produced, is 



the 40o-gallon square-iron tank, which holds approximately 800 pounds of material when filled for open firing. 



f This matter is more fully considered in the early article dealing with the comparative constancy of 



specific characters of Eucalyptus species. 



