September 1910.] 



199 



Oils and Fats. 



The assay of an essential oil is on all- 

 fours with that of a drug or galenical 

 preparation ; when it becomes possible 

 completely and satisfactorily to assay it 

 by chemical means, then, logically, it 

 must cease to have a raison d 1 etre. 



It occasionally happens that the essen- 

 tial oils yielded by two different plants 

 have very similar proximate composi- 

 tions, or have in common a constituent 

 usually adjudged as the most important, 

 yet they may be very readily distin- 

 guished by the nose, and in fact may 

 have widely different monetary values ; 

 perhaps the oil which contains less of the 

 common constituent may even be the 

 higher priced. 



This is actually so with the oils of 

 cinnamon and cassia, and in such a case 

 it becomes of increasing interest and im- 

 portance to examine more closely than 

 usual the chemical and physical charac- 

 ters of the oils and their several consti- 

 tuents. 



As would be expected in such cases, it 

 sometimes happens that the physical 

 characters are similar and that the two 



oils are differentiated analytically only 

 by comparing data for several of the 

 physical and chemical properties, when 

 it will be found that there are slight dif^ 

 ferences always in the same direction 

 which small differences in toto con- 

 stitute an uumistakable differentiation. 

 This is the case with the oils of dill and 

 caraway fruits, but with cinnamon and 

 cassia oils it is not so ; for with the latter 

 pair we have a strongly marked dif- 

 ference in at least one physical property 

 — namely, the refractive index. 



It has recently become fashionable to 

 speak slightingly of the ref ractometer as 

 a weapon in essential-oil analybis ; partly 

 it seems, because everyone does not 

 possess a ref ractometer, and partly, per- 

 haps, because the factor has not opened 

 up a royal road in essential-oil analysis 

 as, when it was first introduced, some 

 persons apparently expected it would. 

 It is, of course, just one physical pro- 

 perty, like specific gravity or optical 

 rotation ; often it is of little value in 

 essential-oil analysis, but sometimes it 

 is very useful, and in the case of cinna- 

 mon oil quite important. 



Table I. 

 Cinnamon-Bark Oij„ 



Sample. 



ft. I. 25° 



Sp. Gr. 



15° 



Aldehyde % 



Eugenol % 



Colour with 

 Fe Cl 3 . 



1. 



1-5753 



1-026 



57-5 



8 



Green. 



2. 



1-5767 



1.0265 



60 



8 





3. 



1-5734 



1-028 



59 



6 



> » 



4. 



1-5727 



1 0265 



58-5 



6 



ti 



5.* 



1-5797 



1-030 



58 



8 



Brownish 





1-5747 



1-029 



58 





green. 



6. 



8 





7.t 



1-5614 



1-003 



50 



8 



1. 

 »» 



8.t 



1*5752 



1-023 



59 



7 



>) 



Coming now to the consideration of 

 this oil in more detail, attention is first 

 called to Table I, which shows analytical 

 data from six samples taken from bulk 

 of cinnamon-bark oil of the choicest 

 aroma, imported in quantity over a 

 series of years, direct from Ceylon, by 

 the British Drug Houses, Ltd., and their 

 predecessors. It will be seen that the 

 refractive index varies only from 1-5727 



to 1-5767, except in the case of one 

 sample which was from a consignment 

 of oil stated to be more than nine years 

 old, where the figure had risen to 1-5797. 

 This particular sample was very resin- 

 ous, from its age. Samples 7 and 8 

 were English-distilled oils of good 

 aroma, the figures for which will be of 

 interest. 



* Nine years old and very resinous. t English- 



