405 



The Pincncs of Eucalyptus Oils. 



DURING this research it has been demonstrated that both laevo- and dextro- 

 rotatory pinenes occur in Eucalyptus oils in varying quantities, from the small 

 amount found in the richer cineol yielding species, to those oils consisting almost 

 entirely of either dextro- or laevo-rotatory pinene. From the leaves of some 

 species an excellent oil of turpentine can be obtained, corresponding to either the 

 American or European varieties, and it thus becomes difficult to determine 

 whether or not a Eucalyptus oil has been sophisticated by the addition of 

 commercial oil of turpentine. If the presence of pinene in quantity were proved, 

 there is still no reason why the oil might not' have been derived entirely from 

 Eucalyptus leaves, and we presume that such a product from such a source must 

 be Eucalyptus oil, even if it consists almost entirely of pinene, like those of 

 E. dextropinea, E. Icevopinea, E. Wilkinsoniana, and others. As these pinene 

 oils necessarily fail to meet the present requirements of the British or American 

 Pharmacopoeias for Eucalyptus oils required for pharmaceutical purposes, they 

 should be exploited in the direction of supplying commercial requirements for 

 turpentine. Whether certain of the non-cineol-bearing .Eucalyptus oils, or those 

 containing but a small amount of that constituent, will eventually be used for 

 medicinal purposes is a matter that has yet to be decided. 



It has been shown in a previous article that the almost transverse 

 parallel venation of Eucalyptus leaves, like those of E. calophylla, E. corymbosa, 

 E. saligna, E. botryoides, &c., is an indication of the presence of a predominance 

 of pinene in their oils, and it was the recognition of this constantly occurring 

 constituent in this group that enabled this peculiarity in the oils of species with 

 this leaf venation to be noted. In all Eucalyptus oils that are rich in cineol, 

 pinene occurs, although in some of them it is present in only small amount. 

 From oils of numerous species it has been isolated and its identity proved by 

 chemical methods, ?.s shown with the pinene which occurs in the oils of 

 E. saligna, E. robusta, &c. From the results thus obtained it is apparent that 

 the pinenes obtainable from the oils of the Genus Eucalyptus (N.O. Myrtaceae) 

 are chemically identical with those obtainable from the Genus Pinus (N.O. 

 Coniferae.). In the oils of Eucalyptus species that connect the large group of 

 " Boxes " with the " Gums," as E. conica, E. Bosistoana, E. quadrangulata, 

 E. propinqua, and others, the presence of pinene is pronounced, as might be 

 expected from their closer proximity to the pinene group, and consequently 

 these oils are on the border line which separates oils capable of passing the 

 present standard, from those lower in this respect. The oils of the species 

 belonging to this group all contain a fair amount of cineol, and the terpene 

 phellandrene is entirely absent, or at the most only present in traces in 

 rare instances. The predominant pinene in these oils is invariably the dextro- 

 rotatory one, and this is also true for oils belonging to the richer cineol class, 

 but often the pinene of opposite rotation is present in such amount as to cause 

 the oil to be almost inactive, and yet for it to be poor in cineol ; for this reason 

 the value of the test of optical rotation for Eucalyptus oils is limited in value, 

 as it may be misleading. If the pinene found in Eucalyptus oils always rotated 

 the ray in the same direction the test would be of greater value, but this is not 

 the case, and in this respect the pinene differs from the phellandrene which 

 appears always to be L-evo-rotatory in Eucalyptus oils. 



By the discovery of the pinene yielding oils, such as those of E. dextro- 

 pinea and E. Icevopinea, it has been possible to investigate somewhat completely 

 the properties of the Eucalyptus pinenes. (See paper Proc. Roy. Soc., N.S.W., 



