Chemistry of Essential Oils

222 THE CHEMISTEY OF ESSENTIAL OILS

Japanese Peppermint Oil.—This oil, as mentioned above, is distilled

from Mentha arvensis (Mentha canadensis), and forms an important

Japanese industry. The most important modern contribution to the

literature of this oil is by Naojiro Inouye.

1

Nagasaki

2

describes the four

following varieties of the plant which are cultivated :—

1. Akamaru.—The leaves of this plant are round, the stalk is reddish-
   violet, and the flowers of a violet colour. The yield of oil and menthol
   is greater in this than in the other varieties.


2. Aomaru.—The leaves are round, the stalk is blue, and the flowers
   violet.


3. Akayanagi.—The leaf is violet on the under surface, the stalk is
   blue and the flower white. The yield of oil is low.


4. Aoyanagi.—This variety resembles the wild plant. Its stalk is
   blue and flower white.
   The following details^3 of peppermint cultivation are o'f interest;
   " Peppermint is cultivated in different parts of Japan, mostly on the hill-
   sides, although that grown on low-lying ground which can alternately
   be used for rice is richest in crystals. As the-oil which has been freed
   from menthol crystals is inferior both in taste and odour to English and
   American oil, experiments have been made in the cultivation of English
   and American peppermint, but unfortunately without success. The best
   oil is produced in the districts 'of Okayama and Hiroshima, where three
   cuts are made yearly: in May, June, and August. The first cut yields
   about 47 per cent, of crystallised menthol (i.e., by freezing only), the
   second about 53 per cent., and the third about 60 per cent. In the dis-
   trict of Yamagata only two, and in Hokkaido only one cut is made, but
   in the last-named district the area under cultivation is considerably larger
   than in the other, so that, in spite of a single crop and a crystallised-
   menthol-yield of only 45 per cent., more than one-half of the total output
   of menthol is produced in the province of Hokkaido.
   " The method of distilling is the same everywhere. It lasts four hours,
   the yield from 82 Ib. of dry leaf of the first cut being 14, of the second
   24, and of the third 21 oz. of oil, or 107, 183, and 1

• 60 per cent, respec-
  tively. The value of course fluctuates, being dependent both upon the
  quality and the dryness of the leaves. The second cut is always the
  most prolific; thus, for example, a field which produces 300 Ib. of leaves
  in the first cut will yield 800 Ib. in the second and 600 Ib. in the third.
  The production per acre is about 5000 Ib. of dry leaves, yielding about
  80 Ib. (= 1-60 per cent.) of oil.
  " The price of the leaves, like that of the oil, varies and the distillers
  •only make small profits. The oil is collected by brokers, and resold to
  the large refineries, of which there are two of importance. In the dis-
  tricts of Odashitsuki, Okujoto, and Bingo there are so-called peppermint-
  guilds, who test the oil and give certificates of weight and purity. In
  the other districts the refiners must take the oil as it comes."
  E. Marx^4 has made an elaborate report on the distillation of the oil
  in Japan.
  From this report it appears that the industry has not benefited by the
  introduction of European methods, although it is a considerable one.

1
Communication from the Laboratory of Prof. Kremers, Madison, Wisconsin,
1908.
a
Yamagata, S. 1.
3
Board of Trade Journal, 79 (1912), 78.
4
Gessell. fur Natur. und Volkirkunde Ostasiens (1896), 6, 355.