Chemistry of Essential Oils

68 THE' CHEMISTEY OF ESSENTIAL OILS

contained in it is lower than that indicated by analysis. This is due to

the presence of a compound, or a mixture of compounds, distilling at a

higher temperature than geraniol and susceptible to acetylation, which

they are further investigating.

Geraniol can also be directly estimated by the followingl process :—

Two grms. of the oil are heated with 2 grms. of phthalic anhydride

and 2 c.c. of benzene for two hours on a water-bath. The mixture is

allowed to cool, and shaken for ten minutes with 60 c.c. of semi-normal

aqueous caustic potash, in a stoppered flask. At the end of this time

the anhydride is converted into neutral phthalate, and the acid geranyl

ester into its potassium salt. The excess of alkali is titrated with semi-

normal sulphuric acid. By deducting from the proportion of alkali

absorbed by the quantity of phthalic anhydride used, the quantity of

alkali used up in the experiment, the quantity of alkali absorbed by the

geranyl ester is obtained, and hence the percentage of geraniol can be

calculated. The results of this method applied to the above mixtures

were as follows :—

I. Geraniol present, 45 per cent.

II. „ „ 40 „

Pound, 47-9 per cent.

41-1

The slightly high results are evidently due to the fact that the

citronellal contained a small proportion of alcohols which react with

the phthalic anhydride.

Schimmel & Co. examined five samples of Ceylon oil by the above

method, and give the following results :—

Specific

Gravity.

0-9012

0-9016

0-9034

0-9039

0-9033

Rotation.

• 11° 22'


• 11° 28'


• 11° 40'
  11° 43'


• 11° 31'

Total

Acetylisable

Constituents

54-1 per cent.

57-2

58-6

56-3

57-6

Geraniol.

30*7 per cent.

33-2

30-0

29-8

30-8

Citronellal.

Kleber's

Method.

ll'i per cent.

11'O

11-6 ,,

10-8

11 5

Dupont's

Method.

7'9 per cent.

8'0

7-K

6-7

7-9

For other methods, which do not appear to be of great practical
value, papers by Kleber^2 and Boulez^3 may be consulted*.
Ceylon citronella oil contains about 10 to 15 per cent, of terpenes,
wrhich include camphene, Z-limonene, and dipentene. Geraniol, borneol,
citronellal, methyl-eugenol, methyl-heptenone, isoamyl alcohol, isovaleric
aldehyde, valeric acid esters, a-terpineol, thujone (?), nerol, esters of
citronellal, farnesol, a mixture of at least two sesquiterpenes (one of low
and the other of high specific gravity), and a terpene of very low specific
gravity have all been detected in this oil.^4

JAVA CLTKONELLA OLL.
This oil is distilled from Cymbopogon nardus in Java, the grass being
of the Maha Pangiri type. The Singapore distilled oil is of almost
exactly the same character.

(^1) Schimmel's Report, October, 1912, 43.
(^3) Bull. Soc. Chim., iv. 11 (1912), 915. * American Perfumer,J Schimmel's Report, April,^6 (1912), 1912, 284. 44.