438 ODOKOGKAPHIA. 



" The two first oils (on Table I.) prove that all oils of high ester- 

 proportion distinguish themselves from the varieties containing less 

 ester by their higher specific gravity and their greater solubility in 

 80 % alcohol. Our own pressing (Table I. Xo. 1) contains a higher 

 ester percentage and a higher specific gravity than all other oils at 

 present known to us, even from the best sources. It is j^'i'ohahle 

 that an entirely unmixed Bergamot oil is never seen in commerce. 



" The third table shows, by means of the control experiments, 

 that the addition of Turpentine, Orange oil or Lemon oil, can be 

 proved convincingly by the determination of the ester percentage. 



"As the intensity of the aroma and therefore the value of 

 Bergamot oil depend solely upon the quantity of Linalool-acetate 

 which it contains, we must consider the determination of the ester 

 percentage to be the decisive test of quality, and may fix the 

 minimum at 38 per cent, of Linaool-acetate. The sp. gr. should 

 not be below 0-881 at 15*^ C. nor the specific rotation higher than 

 20^ (100 m. m.). These requirements, as shown by Table I., are 

 very moderate, and will soon have to be made more severe, in the 

 interests of genuine manufacture. 



"Table III. explains the changes which Bergamot oil experiences 

 by steam-distillation. The abnormally low ester-percentage of the 

 oils distilled from the residue of the pressing, or of the rectified 

 oils, shows that all distilling operations are injurious. In practice 

 this has long been admitted, otherwise the much easier process of 

 distilling the oil instead of pressing it by hand would certainly 

 have been preferred. Owing to its poverty in ester the distilled 

 oil only possesses a very slight Bergamot aroma and much more 

 resembles in fact, Lign-aloe oil ; also its specific gravity and 

 behaviour towards acetic anhydride show it to be rich in Linalool. 



A distilled oil which only contained 12 per cent, of ester, 

 showed, after treatment with acetic anhydride (as above-explained, 

 on Lavender oil), a proportion of 61-5 per cent, of Linalool-acetate. 

 Pressed Bercjamot oil also contains a little free Linalool ; an oil of 

 37 per cent, contained after this treatment, 47 per cent, of ester. 



It may be taken for granted that the Bergamot oil 

 manufacturers use the oil distilled from the residue of the pressing, 

 to mix with the pressed oil. This is the explanation of the low 

 ester percentage and the low specific gravity of the connnercial 

 oils as compared with the oil pressed by us. 



