LABIATE 227
Umney
1
heats 1 c.c. of the oil with 0*5 gram of a mixture of equal
parts paraformaldehyde and citric acid over a water-bath. With
Japanese peppermint oil there is no coloration, whereas with American,
English, Italian, and Saxon oils a purple colour develops.
If five drops of oil are dissolved in 1 c.c. of glacial acetic acid a blue
colour results within one hour with peppermint oils, except in the case
of Japanese oil.
Many experiments have been undertaken with a view to transport
peppermint plants from a country where the oil has developed a parti-
cularly fine odour and flavour, into other countries. Few plants, how-
ever, appear to alter to so great an extent under these conditions as those
of the natural order Labiatae, and when once the soil and climate suit the
plant, transplanting it to different conditions causes the oil to assume
different characters. Thus Mitcham plants, transplanted to France, will
not yield an oil which is necessarily identical with Mitcham oil. Eecent
experiments, however, have been to some extent successful, and oils
having characters very similar to English oil have been obtained from
Mitcham plants grown in Italy. The most complete experiments, how-
ever, in this direction have been carried out with Japanese plants by
Thorns,
2
with a view to determine whether oil containing as much
menthol as is present in Japanese oil could be obtained in Germany or
in German colonies. The Japanese plants were cultivated at Dahlem,
near Berlin, and at Okahandja, South-West Africa.
At Dahlem cuttings were made, the first on 17 July and the second
on 10 August. The yield of oil from the July crop was 0 74 per cent.,
and that from the August crop 0624 per cent. The oils had the charac-
ters given below, which are compared with those of the oil distilled from
plants harvested in the summer of 1911:—
Specific Gravity ....
Solidifying-point
Optical Rotation
Acid Value
Ester „.
Acetylation Ester Val
Combined Menthol
Free Menthol.
Total „ueJuly Crop,
1912.0-8987 at 18°
13-5°- 35-22°
2-66
12-96
283-8
3-78 °/o
75-20 °/ 0
78-98 °
August Crop,
1912.0-903 at 16°
14-75°- 35-29°
2-73
13-80
280-1
3-56 '/ 0
75-65 °/ 0
79-21 %
Summer Crop.
1911.0-8954 at 22°
14-5°- 34-75°
4-01
12-74
283-2
3-50 «
75-27 °/ 0
78-82 °/ 0
A sample of oil distilled from plants grown at Witzenhausen, the
yield being just under 1 per cent, on the dry herb, had the following
characters :—
Specific gravity at 15-5°
Solidifying-point
Optical rotation
Acid value
Ester „
Acetylation ester val16
Combined menthol
Free menthol. •
Total „0-9042
14-5°- 35-3°
3-3
15-15
291-6
6-99 per cent.
74-16
81-15
(^1) P. and E-.O.R., 2 (1911), 275.
aH. Thorns, Ber. deutsche pharm. Ges., 20 (1910), 424; Arbeit. Pharm. Instit.
Univ. Berlin, 8 (1911), 93.