Chemistry of Essential Oils

228 THE CHEMISTKY OF ESSENTIAL OILS

In dealing with the experimental cultivation at Okahandja, in German
South-West Africa, the herb was divided into the leaves and the stems,
which were distilled separately. The leaves yielded 1225 per cent, of
oil, and the stems 02 per cent. Calculated on the whole plant the yield
was 0*866 per cent. Both oils were very similar, and were characterised
by a very high menthol value, in each case over 84 per cent. They had
the following characters :—

Specific Gravity at 20°

Solidifying-point.

Optical Rotation.

Acid Value.

Ester „

Acetylation Ester Value

Combined Menthol ......

Free Menthol

Total ...,.,

1

Leaf Oil.

0-904

20*75°

- 35-29°

1-56

8-29

306-6

2-31 °

83-01 °/ 0

85-32 °/ 0

Stem Oil.

0-9000

21°

- 35-3°

2-77

6-15

304-1

1-71 °/ 0

82-93 °/ 0

84-64 °/ 0

No less than 57|i per cent, of menthol could be separated by freezing

from these oils. ''

CHINESE PEPPERMINT OIL.

A small quantity of peppermint oil is distilled in the neighbourhood

of Hong-Kong, from a plant which is, in all probability, Mentha cana-

densis, var. glabrata. This oil has been examined by the Imperial

Institute,

1

by Schimmel & Co.,

2

and by Shino Saki.

3

The three samples

had the following characters:—

Specific gravity

Optical rotation

Menthol as Esters.

Total menthol.

1.

0-918

- 44° 40'

13-55 per cent.

64-24

2.

0-9187

- 44° 2'

12-6 per cent.

64

3.

0-9091

-35°

8-08 per cent.

78-65 „

FRENCH PEPPERMINT OIL.

Peppermint oil is distilled at Grasse, Cannes, Vence, Cagnes, and

Villeneuve-Loubet, as well as in the Basses-Alpes, Var, and Haute-

Garonne, etc. The French varieties of Mentha piperita are not identical

with those cultivated in England. According to A. and E. G. Camus,4

Mentha piperita is not a separate species, but is a hybrid of Mentha

viridis and Mentha aquatica. Two well-defined forms are cultivated

in the south of France which are termed by Camus Mentha piperita

officinalis, var. pallescens, and Mentha piperita officinalis, var. rubescens.

These, however, do not agree in characters with the forms described by

Planchon and Collin as "blanche" and "noire"—nor are they identical

with our own " black " and " white " mints. These facts illustrate the

very great variability of the peppermint plant. The following figures

illustrate the characters of the two oils:—

1

Bull Imp. Inst., 11 (1913), 434.

34 /. Chem. Ind. Tokio, 1919, 22, 458.

Boure-Bertrand Fils, Report, October, 1911, 3.

(^2) Report, October, 1910, 96.