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portion which came over between 170-190 C., being used for the absorption, 

 and the result calculated for the original oil. (See also in this connection C. F. 

 Bennett, " Perfumery and Essential Oil Record," Oct., 1912.) 



With the heavy cineol Eucalyptus oils of the E. polybractea class, in which 

 only a very small portion distils below 170 C., this modified method may 

 succeed in concentrating the cineol, but with the pinene-cineol oils in which a 

 considerable fraction is obtained boiling below 170 C. a good deal of cineol 

 comes over in that portion, and it does not seem possible, by direct distillation 

 of oils of this class, to prevent much cineol distilling over with the pinene 

 in this way. 



With a large number of Eucalyptus oils in which cineol is only present in 

 small amount and other constituents soluble in resorcinol not at all pronounced, 

 the process acts very well, and cineol as low as 5 per cent, can be determined in 

 this way. Such oils are those consisting largely of pinene, as E. dextropinea, 

 E. Icevopinea, &c., and many of the phellandrene-bearing oils, such as E. oreades, 

 E. Delegatensis, E. stelhdata, &c. 



The method was also found useful for comparative purposes, as, for 

 instance, in the investigation of the oils of E. Smithii from various forms of 

 growth (Proc. Roy. Soc., N.S.W., Aug., 1915). Those results are also published 

 in this work. The oil of this species contains a very small amount of substances 

 other than cineol absorbable by resorcinol, and this is also the case with that of 

 E. polybractea and a few others of the richer cineol class. 



The resorcinol method may be considered a useful one for determining 

 the cineol in a number of Eucalyptus oils, and may be satisfactorily employed for 

 that purpose, but is more particularly applicable with those for which the 

 phosphoric acid method is useless. Like all other known methods it is not of 

 universal application, owing to the great diversity of constituents in Eucalyptus 

 oils, and it thus becomes necessary to discriminate when choosing the method 

 to be employed. The resorcinol process is also useful in assisting the investigation 

 of undetermined Eucalyptus oils. 



Unfortunately many constituents which occur in varying amounts in 

 Eucalyptus oils are absorbed by 50 per cent, resorcinol, equally with cineol, and 

 this is the case with the alcohols, as geraniol, terpineol, eudesmol, amyl, butyl, 

 &c. ; the aldehydes as aromadendral, citral, citronellal, butaldehyde, &c. ; the 

 lower esters as amyl-acetate, butyl-butyrate, &c. ; piperitone and other bodies 

 containing oxygen. 



It is thus evident that the resorcinol method cannot be expected to give 

 accurate results with all Eucalyptus oils, particularly those in which the 

 constituents enumerated above occur in quantity, and it is difficult, if not 

 impossible, with the oils of many Eucalyptus species to prepare a fraction in 

 which the whole of the cineol is concentrated, and at the same time for it to be 

 comparatively free from other absorbable constituents. If these are known, 

 however, they can be separately determined, and allowed for, and in this way 

 the cineol results might be made fairly accurate. 



Illustrations of this procedure are given under E. dives, E. piperita, and 

 other species in which the amount of piperitone in the fraction boiling below 

 190 C. was separately determined and allowed for. 



As illustrating the difficulties in this connection the following analyses are 

 given, and the four oils investigated are quite representative of the cineol Eucalyptus 

 oils at present found on the market. The data have been obtained from the 

 rectified oils distilling below 190 C., in order that the results with the rapid 

 phosphoric acid and resorcinol methods might be compared, and the amount of 

 absorbable constituents, other than cineol, indicated. 



50068 2 A 



