Chemistry of Essential Oils

EUTACE^ 445

Oil.

Bergamot (1)

Bergamot (2)

with 5 per Cent. Terpinyl

Acetate ....

with 10 per Cent. Terpinyl

Acetate ....

20 c.c. x

2 hours.

100-5

108

117

121

10 c.c. (and

25 c.c. Alcohol)

x 1 hour.

98-6

105-5

102-5

104-0

Difference.

1-9

2-5

H-5

17-0

The above table represents the behaviour on fractionation at 3 mm.
pressure of two samples of bergamot adulterated with terpinyl acetate and
a sample of pure bergamot oil.
The author has recommended the examination of the last 10 per
cent, left on evaporation of the oil on a water-bath, since the heavy arti-
ficial esters accumulate in this fraction. The refractive index of this 10
per cent, should not be below 15090, and the saponification value should
not exceed 190. The figures given on p. 446 represent nine samples of
adulterated oil, all sold as genuine bergamot oil.
Glyceryl acetate, which is an artificial ester commonly used in the
adulteration of bergamot oil, is detected fairly easily on account of its high
solubility in dilute alcohol. The test is carried out as follows^2 : Ten c.c.
of bergamot oil and 20 c.c. of 5 per cent, alcohol are well shaken in a
separating funnel, and after the solutions have separated and become
clear the watery solution is run off and filtered. Ten c.c. of the filtrate
are exactly neutralised with deci-normal alkali, and then 5 c.c. of semi-
normal alkali run in, and the whole saponified under a reflux condenser
for one hour. In the case of pure bergamot oil 01 or at most 02 c.c. of
semi-normal alkali will have been used up by the saponification, whilst
each 1 per cent, of glyceryl tri-acetate present in the oil will be represented
by practically 0*5 c.c. of semi-normal alkali.

Schimmel & Co. have proposed to detect esters of fixed acids by an.
estimation of the amount of volatile acids obtained by distilling the
acidified saponification residues, and comparing this figure with the
amount of acid indicated by the saponification valued
In this determination about 2 grams are saponified in the usual
manner, and the saponification residue rendered slightly alkaline, and
evaporated to dryness on a watsr-bath. The residue is dissolved in 5 c.c..
of water and acidified with 2 c.c. of dilute sulphuric acid. This liquid is
now distilled by passing a current of steam through it, and when no
further acid comes over, the distillate (about 300 c.c.) is titrated with deci-
normal alkali, using phenolphthalein as indicator. The alkali consumed in
this neutralisation is nearly identical with that used in the direct saponi-
fication, if all the esters present are those of volatile acids, as is the case
with pure bergamot oil. The distillation value should not be more than
5 to 10 below the direct saponification value (i.e. milligrams of KOH per
1 gram of oil). When esters of non-volatile acids have been used as
adulterants the difference is enormous. For example, an oil co ntaining.
2 per cent, of ethyl citrate yielded a direct saponification valueo f 109*1

(^1) P. and E.O.R. (1911), 14.^2 SchimmQl'sBericht, April, 1911, 151.