— 57 — 



I. d 15 o 0,8834, « D + 18° 45', acid no. 0,9, ester no. 101,0 = 35,4% ester 



(calc. for linalyl acetate), residue of evaporation 6°/ , soluble in 



0,3 vol. and more of 90% alcohol. 

 II. disc 0,8838, « D + 20°, acid no. 1,8, ester no. 100,2 = 35,1 °/ ester, 



residue of evaporation 6,2%, soluble in 0,3 vol. and more of 90° 



alcohol. 

 With the exception of the residue after evaporation of sample No. II 

 the properties enumerated above lie within the limits applicable to com- 

 mercial oils (di 5 o 0,881 to 0,886; « D + 8 to +24°; linalyl acetate not less 

 than 34%; residue of evaporation 4,5 to 6%), but both oils contained 

 citric acid which had obviously been added in the form of tri-ethyl citrate. 

 By working with 100 g. of the oil it was even possible to isolate the acid. 

 It was then found that citric acid ester which has been added to oil 

 of bergamot remains behind in the residue when the oil is evaporated in the 

 water-bath, and can there be detected by the increase in the saponification 

 number. Thus a ready means is at hand for proving any adulteration of 

 this description. Experiments showed that almost the whole of the citric 

 acid ester remains behind, from which it follows that the saponification 

 number of the residue makes it possible to form an approximate estimate 

 of the quantity of the ester added. 



This determination is carried out as follows: 5 g. bergamot oil is 

 evaporated in a metal dish on the water-bath until the weight remains 

 constant, which takes from 4 to 5 hours. The residue is washed quanti- 

 tatively with alcohol in a saponification flask and saponified in the cus- 

 tomary manner with semi-normal potash solution. After cooling, the excess 

 of alkali is titrated back with seminormal sulphuric acid, additing phenol- 

 phthalein as indicator. If, in the process of titration, the liquid should 

 acquire a red tint after some time no attention need be paid to this, the 

 original decoloration being the only factor to be taken into consideration. 

 The reddening is due to the tardy elimination of alkali from the bergaptene, 

 which has been split up into bergaptenic acid. The recurrence of the 

 reddening may be obviated to a certain extent by abstaining from diluting 

 the liquid with water before it is titrated. 



The saponification numbers of the residues of evaporation of pure 

 bergamot oil ranged from 136 to 180, but in the case of the two adulte- 

 rated oils referred to above they were 253,8 (No. I) and 261,9 (No. II), 

 that is to say, very decidedly above the normal. For purposes of com- 

 parison we added to pure natural oil, of which the residue of evaporation 

 was 5,2% (sap. no. of the said residue 174,5), 1% triethyl citrate and 

 then found the residue of evaporation to be 6% and its sap. no. 222,2. 

 That is to say, the residue gave an increase of 0,8%, equivalent to almost 

 the whole of the triethyl citrate added, while the saponification number 

 of the residue of evaporation showed an increase of 222,2 — 174,5 = 47,7. 

 The addition of 2% triethyl citrate to the original oil gave corresponding 



