355 



b OIL OF / POLYBRAi II I. 



At 22-5 C. = 1-4572 ] ,, , . 



■ I 1 St Mean alteration for e i< li 



0-0 C! C-44Q1 (* """" 1V 



[0-0° C. 1 ■ |.v,7 J 



o-ood 17 



(c) OIL OF E. DIVES. 



At 20-0° C. = 1-4793 " 



39-0° C. = 1-4706 Mean alteration I01 each 



7,7-0° C. = r'4713 }■ degree, approximately 



34-0° C. = 1-4727 0-00047. 



31-0° C. = 1-4741 J 



The above results indicate that 0-00047 ' s , ' l( ' mran alteration in refraetive 

 index [or each degree of temperature for ordinary Eucalyptus oils, and this 



correction has heen employed in this work for standardising the oils at 20° C. 



Eucalyptus Oils and their Constituents. 



The constituents detected in Eucalyptus oils now number about forty. 

 .Manx of them, however, are identical with similar substances occurring in 

 other essential oils, and are thus obtainable from other sources, although, with 

 several of them, much less advantageously. 



The following list includes practically all the constituents so far deter- 

 mined, many of which have been brought to light during these researches. They 

 are found in the oils of the different Eucalypts in varying quantity, occurring 

 more abundantly in some species than in others. It is now known, however, 

 from which investigated species the desired constituents can be most readily 

 obtained, and in the greatest quantity, particularly as those characteristic of 

 specific oils arc comparatively constant. 



Although the main constituents in the several oils have been determined, 

 yet, in many cases, it is difficult to say with certainty that all have been 

 < ! ' tected, and it is possible that some do occur in small amounts in the oils of 

 species in which they have not, so far, been found. 



During the last twenty-five years, however, much work has been done 

 upon the products oi the Eucalypts, and our knowledge concerning the 

 constitution o| their oils is now such thai it lias been possible to evolve some 

 order with the several members of this extensive genus. 



EARLIER INVESTIGATIONS. 



I lie firs1 investigation oi a Eucalyptus oil was undertaken by M. Cloez 

 (Compt. Rend., 1870, p. 687) upon the oil of E. globulus. Trees of this species of 

 Eucalyptus had for some years previously been successfully cultivated in many 

 parts ot Europe, although the young shoots of the trees grown at Paris did not 

 withstand the frost, and it was due to this circumstance that (doc/ was led 

 to investigate the essential oil obtainable from the leaves. It was from this. 



