Chemistry of Essential Oils

LABIATE 239

time of harvest, drying, and freezing of spearmint, on the yield and

odorous constituents of the oil. He gives the following characters for

typical oils distilled from the plant at different stages of its development.

He finds the oil from the fruiting herb more fragrant than that from

the budding or flowering plant. Oil distilled from the leaves and tops

are richer in esters than the oil from the whole plant. Eabak concludes

that the yield of oil is affected by seasonal conditions, being much higher

in some seasons than in others. The maximum yield is obtained during

the flowering period. Drying the plants results in a lower yield, and

freezing causes the oil to contain more esters and alcohols.

Year and Description

of Material.

1908.

Fresh Herb :

Budding.

Flowering

Fruiting.

1909.

Fresh Herb :

Budding.

Flowering

Fruiting.

Budding.

Flowering

Fruiting.

1910.

Fresh Herb:

Budding.

Flowering

Fruiting.

Dried Herb :

Budding.

Flowering

Fruiting.

Specifi

Gravity.

0-925 at 22°

0-929 „

0-929 „

0-931 at 21°

0-929 ,

0-934 ,

0-928 ,

0-933 ,

0-925 ,

0-931 at 23°

0-925 „

0-930 „

0-912 „

—

0-916 „

Optical

Rotation.

- 25-1°

- 24-5°

- 21-7°

- 16-3°

- 16 1°

- 17-4°

- 17°

- 17-5°

- 16-5°

- 22-8°

- 20-3°

—

- 18-2°

Refractive

Index.

1-4874 at 24°

1-4880 „

1-4853 „

1-4891 at 21°

1-4864

1-4873

1-4888

1-4868

1-4846

1 -4895 at 23°

1-4825 „

1-4800 „

1-4775 „

1-4788 ,,

1-4745 „

Esters as

Acetate of

3-8 °/ 0

4*6 7.

8-7 °/D

8-6 °/ 0

7-7 °/ 0

7-3 %

7-0 °/0

10-8 °/ 0

9*1 7O

7*6 °/

13-4 °/°

15-9 °/ 0

10-8 7O

31-8 °/ 0

22-0 °/ 0

Total

Alcohols

as

C]0H 18 0.

9-1 7O

8-54 °

13-4 7O

12-0 °/ 0

12-4 °/ 0

10-9 7O

11-7 °

12-7 7 8

15-6 %

16 7o

18-4 7O

21-4 7O

15-7 7

28-2 7O

30-5 7O

Eussian spearmint oil contains, according to Schimmel & Co.,

1

50 to

60 per cent, of Z-linalol. Cineol, Z-limonene, and carvone are also present.

OIL OF MENTHA AQUATICA.
The dried herb, Mentha aquatica, the water mint, yields about 0 4
per cent, of essential oil, having an odour of pennyroyal. The characters
'Of the oil are not well determined. An oil distilled by Schimmel & Co.
had a specific gravity 0880 and optical rotation - 2° 14', whereas a
sample examined by Tschirch had a specific gravity 09553, optical
rotation + 64° 56', and refractive index 14827.
Irk^2 found a Hungarian oil to have a specific gravity 09603, optical
rotation + 2273°, and refractive index 1*4900.

(^1) Bericht, April, 1898, 28.

. Zentral., 52 (1911), 1113.