Chemistry of Essential Oils

ZINGIBEBACEJE 99

The oil has the following characters :—

Specific gravity0-8740t

Optical rotation-25°

Eefractive index 1-4885

Acid value ........

Ester „ 1

,, ,, (after acetylation) .....

Abnormal ginger oils are from time to time to be found,

reports on a sample distilled in the Philippines, having an optical rota-

tion of + 5

*

9°, and a Japanese oil has been found having a specific

.gravity 0*894 and an optical rotation + 9° 40'. A Java oil has been re-

corded

2

with a rotation of + 13° 9'. Thresh has fractionally distilled a

specimen of this oil prepared in England from the dried root, and ob-

tained the following results :—

0-8740 to

• 25° -5
  1-4885 1
  0 2
  1 »
  30 „

-886

- 50°

1-4950

2

15

45

be found. Baconl

Below 150°.

150

°

to 200°

200° „ 240°

240° „ 265°

265° „ 300° ....

Residue

5 per cent.

. 10
8 „
60
7
10 „
These results, however, must be accepted with reserve, as the oil
undergoes decomposition by distillation at ordinary pressure. The
fraction obtained at 155° to 165° is usually dextro-rotatory.
Dextro-camphene and /2-phellandrene constitute the bulk of the ter-
penes present in the oil. Cineol, citral, and borneol have been identified,
with possibly traces of geraniol. Van Soden and Kojahn^3 have isolated
;a sesquiterpene which they have named zingiberene. This body has a
specific gravity 0872, optical rotation - 69°, and boils at 269° to 270°.
Dodge
4
has isolated a small quantity of an aldehyde, which appears
to be decyl aldehyde. Brooks^5 has identified methyl-heptenone, nonyl
aldehyde, linalol, acetic and caprylic esters, a phenol (chavicol ?), and a
sesquiterpene alcohol having the characteristic odour of the oil. This
body C 15 H 26 O, which has been termed zingiberol, boils at 154° to 157° at
145 mm. pressure.

OIL OF GALANGAL.

This oil is obtained from the rhizome of Alpinia officinarum, a plant

•cultivated in China and Siam. The oil is obtained by moistening the

ground rhizomes with water, and after some hours distilling them with

steam. The oil is of a greenish-yellow colour, with a sharp taste and

pungent camphoraceous odour. The yield is from *5 to 1*5 per cent.

The oil has the following characters :—

Specific gravity

Optical rotation

Refractive index

Acid value

Ester ,,

,, ,, (after acetylation).

The constituents of galangal oil so far identified, are cineol, d-a-

pinene, cadinene, together with the following compounds described by

(^1) Philipp. Jour., Sci.
t^5 (1910), 259.
iJaarb. dep. Landb. Ned. Ind. Batavia (1912), 57.
zpjiarm. Zeit., 45 (1900), 414. 4 chem. Zeit., 34 (1912), 1217.
5Jour. Amer. Chem. Sos., 38 (1916), 430.

. 0-915 to 0*925

• 1°
  . 1-4760
  0 ,
  6 ,
  40 ,

, - 6°

, 1*4825

, 2

, 15

, 50